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Dissertations / Theses on the topic 'Quantum sensing'
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Santos, Marcílio Manuel dos. "Quantum precision sensing." Thesis, University of Aberdeen, 2014. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=215279.
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Zhuang, Quntao. "Quantum enhanced sensing and communication." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119115.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references.
Quantum phenomena such as entanglement and superposition enable performance beyond what classical physics can provide in tasks of computing, communication and sensing. Quantum sensing aims to enhance the measurement precision in parameter estimation or error probability in hypothesis testing. The first part of this thesis focuses on protocols for entanglement-enhanced sensing. However, various quantum sensing schemes' quantum advantage disappears in presence of decoherence from noise and loss. The quantum illumination protocol, on the other hand, has advantage over classical illumination even in presence of decoherence. This thesis provides the optimum receiver design for quantum illumination, and extends quantum illumination target detection to the realistic scenario with target fading and the Neyman-Pearson decision criterion. Quantum algorithms can solve difficult problems more efficiently than classical algorithms, which makes various classical encryption schemes vulnerable. To remedy this security issue, quantum key distribution enables sharing of secret keys with unconditional protocol security. However, the secret-key-rate of the state-of-art single-mode based quantum key distribution protocols are limited by a fundamental rate-loss trade-off. To enhance the secret-key-rate, this thesis proposes a multi-mode based quantum key distribution protocol. To prove its security, the noisy entanglement assisted classical capacity is developed to enable a security framework for two-way quantum key distribution protocols such as the one proposed here. An essential notion in the entanglement assisted capacity is additivity. This thesis constructs a channel with non-additive classical capacity assisted by limited entanglement assistance, even when the classical capacity of the channel is additive.
by Quntao Zhuang.
Ph. D.
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Fernández, Lorenzo Samuel. "Exploiting symmetry and criticality in quantum sensing and quantum simulation." Thesis, University of Sussex, 2018. http://sro.sussex.ac.uk/id/eprint/81274/.
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Decoherence and errors appear among the main challenges to implement successful quantum technologies. In this thesis I discuss the application of some general tools and principles that may be valuable resources to develop robust technologies, with applications in quantum sensing and quantum simulation. Firstly, we employ suitable periodically driving fields acting on the Ising model in order to tailor spin-spin interactions depending on the spatial direction of the bonds. In this way, we are able to simulate the quantum compass model on a square lattice. This system exhibits topological order and a doubly degenerate ground state protected against local noise. A possible implementation of this proposal is outlined for atomic quantum simulators. Secondly, we exploit two general working principles based on spontaneous symmetry breaking and criticality that may be beneficial to achieve robust quantum sensors, particularly appropriate for quantum optical dissipative systems. A concrete application is given for a minimal model: a single qubit laser. It is shown how the precision in parameter estimation is enhanced as the incoherent pumping acting on the qubit increases, and also when the system is close to the lasing critical point. Finally, classical long-range correlations in lattice systems are shown to provide us with an additional resource to be used in robust sensing schemes. The previous setup is extended to a lattice of single qubit lasers where interactions are incoherent. Under the right conditions, we show that a Heisenberg scaling with the number of probes can be accomplished.
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Mulrooney, Ray. "Analyte sensing with luminescent quantum dots." Thesis, Robert Gordon University, 2009. http://hdl.handle.net/10059/452.
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Semiconducting nanocrystals otherwise known as Quantum Dots (QDs) have attracted considerable attention over the last number of years due to their unique optical properties and potential applications. Their narrow size-tunable emission spectra, broad absorption spectra, resistance to photobleaching and long fluorescent lifetimes make them ideal for sensing ions and small molecules. This thesis explores the potential of QDs to function as the emissive unit in fluorescent probes. Primarily, the focus of the work is to develop QD-based sensors that operate through an electron transfer mechanism. Chapter 3 discusses the synthesis and characterisation of CdSe and CdSe/ZnS QDs. Three different sized QDs were prepared each with distinct emission wavelengths. The sizes of these nanoparticles were determined by three methods, transmission electron microscopy (TEM), dynamic light scattering (DLS) and by a UV-vis method. Surface functionalisation of these synthesised QDs (chapter 4) with mercaptosuccinic acid rendered them water soluble and were shown to display selectivity for Cu2+ over a number of biologically relevant metal ions. The negatively charged surface of the QDs and the position of copper in the Irving-William series were believed to be responsible for this interaction. Positively charged CdSe/ZnS QDs were also prepared and were shown to detect ATP and to a much lesser extent GTP over the other nucleotides screened. The greater net negative charge of the ATP and GTP when compared to their mono and diphosphate analogues was the likely cause of this discrimination. In chapter 5 the relatively unexplored field of anion sensing with QDs was examined using charge neutral urea and thiourea receptors. Based on a design by Gunnlaugsson et al, a CdSe/ZnS QD with a thiourea receptor anchored to its surface displayed similar PET-mediated fluorescence quenching as an organic dye sensor containing the same receptor. A ferrocenyl urea receptor was also anchored to a QD surface and shown to “switch off” the QD’s fluorescence emission. On addition of fluoride ions the emission was restored, most likely due to a modulation of the ferrocene’s redox activity. In chapter 6 the assembly of Schiff base receptors on the surface of preformed CdSe/ZnS QDs were shown to arrange in such a way to enable the simultaneous detection of Cu2+ and Fe3+. The intriguing aspect of this study was that the receptors themselves displayed no selectivity for any metal ion until they were assembled on the QDs. Recognition was also confirmed by a distinct colour change visible to the naked eye.
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Hay, Kenneth Gillespie. "Gas sensing using quantum cascade lasers." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=12766.
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Ajoy, Ashok. "Quantum assisted sensing, simulation and control." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107326.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 453-485).
This thesis describes experimental and theoretical work making contributions with the aims of improving and advancing techniques of quantum metrology, simulation and control. Towards this goal, we engineer novel devices for quantum sensing, particularly the measurement of rotations, magnetic fields, and single spins towards the reconstruction of single-molecule structures. We also develop new methods that aid these tasks. For instance, we demonstrate how versatile quantum control of spin systems can be achieved via Hamiltonian engineering based on the creation of dynamical filters and/or the use of a quantum actuator, with novel implications in quantum simulation. We also enhance the available quantum control, sensing and simulation methods by the use of ancillary systems, for instance an electronic quantum actuator and a nuclear quantum memory. Finally, by revisiting old techniques in nuclear magnetic resonance, we develop novel insights and measurement protocols on single-spin quantum systems.
by Ashok Ajoy.
Ph. D.
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Dietsche, Eva-Katharina. "Quantum sensing with Rydberg Schrödinger cat states." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066211/document.
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Les atomes de Rydberg sont des états très excités, dans lesquels un électron est placé sur une orbite éloignée du noyau. Leur grand dipôle électrique les rend très sensibles à leur environnement électromagnétique. En utilisant des champs microondes et radiofréquences, nous préparons des états quantiques non-classiques spécialement conçus pour exploiter au mieux cette sensibilité et mesurer des champs électriques et magnétiques avec une grande précision. Dans la première partie, nous préparons des états chats de Schrödinger, superpositions d'orbitales de polarisabilités très différentes, qui nous permettent de mesurer de petites variations du champ électrique statique avec une sensibilité bien supérieure à la limite quantique standard et proche de la limite Heisenberg fondamentale. Nous atteignons une sensibilité par atome de 30mV/m pour un temps d'interrogation de 200ns, faisant de notre système l'un des électromètres les plus sensibles à ce jour. Nous implémentons ensuite des manipulations plus complexes de l'atome. Grâce à une technique d'écho de spin qui exploite la richesse de la multiplicité Rydberg, nous mesurons les corrélations temporelles du champ électrique avec une bande passante de l'ordre du MHz. Dans la partie finale, nous préparons une superposition quantique de deux états circulaires de nombres quantiques magnétiques opposés. Cet état très non-classique correspond à un électron tournant à la fois dans des directions opposées sur la même orbite. La grande différence de moment magnétique entre les deux composantes de la superposition, de l'ordre de 100muB, ouvre la voie à la mesure de petites variations du champ magnétique avec une grande bande passanteRydberg atoms are highly excited states, in which the electron is orbiting far from the nucleus. Their large electric dipole makes them very sensitive to their electromagnetic environment. Using a combination of microwave and radio-frequency fields, we engineer non-classical quantum states specifically designed to exploit at best this sensitivity for electric and magnetic field metrology. In the first part, we prepare non-classical states, similar to Schrödinger cat states, superpositions of two orbitals with very different polarizabilities, that allow us to measure small variations of the static electric field with a sensitivity well beyond the standard quantum limit and close to the fundamental Heisenberg limit. We reach a single atom sensitivity of 30mV/m for a 200ns interrogation time. It makes our system one of the most sensitive electrometers to date. We then implement more complex manipulations of the atom. Using a spin-echo technique taking advantage of the full extent of the Rydberg manifold, we perform a correlation function measurement of the electric field with a MHz bandwidth.In the final part, we prepare a quantum superposition of two circular states with opposite magnetic quantum numbers. It corresponds to an electron rotating at the same time in opposite directions on the same orbit, a rather non-classical situation. The huge difference of magnetic moment between the two components of the superposition, in the order of 100muB, opens the way to the measurement of small variations of the magnetic field with a high bandwidth
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Maurer, Peter. "Coherent control of diamond defects for quantum information science and quantum sensing." Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11431.
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Quantum mechanics, arguably one of the greatest achievements of modern physics, has not only fundamentally changed our understanding of nature but is also taking an ever increasing role in engineering. Today, the control of quantum systems has already had a far-reaching impact on time and frequency metrology. By gaining further control over a large variety of different quantum systems, many potential applications are emerging. Those applications range from the development of quantum sensors and new quantum metrological approaches to the realization of quantum information processors and quantum networks. Unfortunately most quantum systems are very fragile objects that require tremendous experimental effort to avoid dephasing. Being able to control the interaction between a quantum system with its local environment embodies therefore an important aspect for application and hence is at the focus of this thesis.Physics
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Spedalieri, Gaetana. "Quantum hypothesis testing : theory and applications to quantum sensing and data readout." Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/13736/.
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In this thesis we investigate the theory of quantum hypothesis testing and its potential applications for the new area of quantum technologies. We first consider the asymmetric formulation of quantum hypothesis testing where the aim is to minimize the probability of false negatives and the main tool is provided by the quantum Hoeffding bound. In this context we provide a general recipe for computing this bound in the most important scenario for continuous variable quantum information, that of Gaussian states. We then study both asymmetric and symmetric quantum hypothesis testing in the context of quantum channel discrimination. Here we show how the use of quantum-correlated light can enhance the detection of small variations of transmissivity in a sample of photodegrabable material, while a classical source of light either cannot retrieve information or would destroy the sample. This non-invasive quantum technique might be useful to realize in-vivo and real-time probing of very fragile biological samples, such as DNA or RNA. We also show that the same principle can be exploited to build next-generation memories for the confidential storage of confidential data, where information can be read only by well-tailored sources of entangled light.
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Charlton, Christy. "Quantum Cascade Lasers for Mid-Infrared Chemical Sensing." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/13953.
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The mid-infrared (MIR) spectral range (2-20 m) is particularly useful for chemical sensing due to the excitation of fundamental rotational and vibrational modes. In the fingerprint region (10-20 m), most organic analytes have unique absorption patterns; absorption measurements in this region provide molecule-specific information with high sensitivity.
Quantum cascade lasers (QCLs) present an ideal light source for (MIR) chemical sensing due to their narrow linewidth, high spectral density, compact size, and ease of fabrication of nearly any MIR wavelength. As the emission wavelength is dependent on layer size within the heterostructure rather than material composition, various wavelengths in the MIR can be achieved through bandstructure engineering.
High sensitivity measurements have been achieved in both gas and liquid phase by developing integrated sensing systems. The laser emission frequency is selected to match a strong absorption feature for the analyte of interest where no other interfering bands are located. A waveguide is then developed to fit the application and wavelength used.
Gas sensing applications incorporate silica hollow waveguides (HWG) and an OmniGuide fiber (or photonic bandgap HWG). Analyte gas is injected into the hollow core allowing the HWG or OmniGuide to serve simultaneously as a waveguide and miniaturized gas cell. Sensitivities of parts per billion are achieved with a response time of 8 s and a sample volume of approximately 1 mL.
Liquid sensing is achieved via evanescent wave measurements with planar waveguides of silver halide (AgX) and gallium arsenide (GaAs). GaAs waveguides developed in this work have a thickness on the order of the wavelength of light achieving single-mode waveguides, providing a significant improvement in evanescent field strength over conventional multimode fibers. Liquid samples of L volume at the waveguide surfaces are detected.
QCLs have begun to be utilized as a light source in the MIR regime over the last decade. The next step in this field is the development of compact and highly integrated device platforms which take full advantage of this technology. The sensing demonstrations in this work advance the field towards finding key applications in medical, biological, environmental, and atmospheric measurements.
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Higgins, Kieran. "Quantum technologies for enhanced sensing and light absorption." Thesis, University of Oxford, 2014. https://ora.ox.ac.uk/objects/uuid:f21e691a-f83e-4c9f-bc51-d94c4703e16e.
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The counterintuitive properties of quantum mechanics have the potential to produce revolutionary new technology. The applications of these devices are both vital and diverse: the efficient generation of energy from light, sensing and measuring with exquisite precision, and information processing with unparalleled speed. In this thesis, I use the theory of open quantum systems to investigate quantum technologies for enhanced sensing and light absorption. In the first research chapter, we develop a new method for describing qubit dynamics in the Rabi model. We obtain a new expression for the ac Stark shift, which enables practical and precise qubit thermometry of an oscillator. In the second research chapter, we demonstrate that it is possible to invert the phenomenon of Dicke Superradiance using nanostructures and quantum control. This creates the possibility of a new class of quantum light absorption technologies with a super-linear scaling in the absorption rate. In the final research chapter, we investigate another means of enhancing light absorption. We show that phonon assisted transitions to ratchet states in rings allow absorbed excitions to be protected from reemission.
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Cooper-Roy, Alexandre. "Coherent control of electron spins in diamond for quantum information science and quantum sensing." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/111688.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 115-122).
This thesis introduces and experimentally demonstrates coherent control techniques to exploit electron spins in diamond for applications in quantum information processing and quantum sensing. Specifically, optically-detected magnetic resonance measurements are performed on quantum states of single and multiple electronic spins associated with nitrogen-vacancy centers and other paramagnetic centers in synthetic diamond crystals. We first introduce and experimentally demonstrate the Walsh reconstruction method as a general framework to estimate the parameters of deterministic and stochastic fields with a quantum probe. Our method generalizes sampling techniques based on dynamical decoupling sequences and enables measuring the temporal profile of time-varying magnetic fields in the presence of dephasing noise. We then introduce and experimentally demonstrate coherent control techniques to identify, integrate, and exploit unknown quantum systems located in the environment of a quantum probe. We first locate and identify two hybrid electron-nuclear spins systems associated with unknown paramagnetic centers in the environment of a single nitrogen-vacancy center in diamond. We then prepare, manipulate, and measure their quantum states using cross-polarization sequences, coherent feedback techniques, and quantum measurements. We finally create and detect entangled states of up to three electron spins to perform environment-assisted quantum metrology of time-varying magnetic fields. These results demonstrate a scalable approach to create entangled states of many particles with quantum resources extracted from the environment of a quantum probe. Applications of these techniques range from real-time functional imaging of neural activity at the level of single neurons to magnetic resonance spectroscopy and imaging of biological complexes in living cells and characterization of the structure and dynamics of magnetic materials.
by Alexandre Cooper-Roy.
Ph. D.
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Zander, Jascha [Verfasser]. "Squeezed and Entangled Light: From Foundations of Quantum Mechanics to Quantum Sensing / Jascha Zander." Hamburg : Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky, 2021. http://d-nb.info/1240386389/34.
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Vaitiekus, Deivis. "Development of quantum cascade lasers for gas sensing applications." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/13916/.
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Quantum cascade lasers (QCLs) are capable of high power, tunable wavelength and single mode emission at room temperature in the mid-infrared wavelength region. These capabilities make them perfect light sources for laser based gas spectroscopy. The work described in this thesis focuses on development of QCLs suitable for selective gas sensing applications. The thesis starts with the description of different changes to the QCL active region design. These changes were studied in order to improve laser performance while keeping the emission wavelength fixed. The proposed modifications were performed on short mid-infrared wavelength (lambda=3-4um) quantum cascade lasers based on InGaAs/AlAsSb and InAs/AlSb material systems. The focus of this work is then moved to the description of a single mode quantum cascade laser with a third order unilateral grating. The previously unreported grating architecture that was used to achieve distributed feedback (DFB) in a QCL, as well as grating design and laser characterization are detailed in Chapter \ref{chap:uni}. The reported laser generates single mode emission with 30 dB side mode suppression ratio and a linewidth of 0.4cm^(-1). The simplified fabrication process for a third order DFB grating is developed for lambda=3.3-3.6um emission wavelength. A different approach to achieve single mode emission in a QCL is described in Chapter 6. An external cavity QCL setup combined with the Fabry-Perot (FP) reflector is reported for the first time. The FP reflector is used to provide selective feedback that is controlled by the separation distance between two FP reflector mirrors. This external cavity arrangement allows generation of a wide spectral range and the rapid wavelength tuning capability. Finally, the thesis is concluded with sensitive gas detection experiments. The direct absorption technique is utilized to demonstrate the 160ppmv detection of methane with the ro-vibrational absorption line located at lambda=3.3um and 1ppmv detection of nitric oxide with the absorption line located at lambda=5.3um. The experiments were performed using single mode lasers that were designed and fabricated in Sheffield.
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Li, Luozhou. "Diamond nanophotonic devices for quantum information processing and sensing." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101573.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 107-123).
The nitrogen vacancy (NV) center in diamond has in recent years emerged as a promising solid state system for quantum information processing and sensing applications. However, using NV centers to build up quantum networks for these applications faces several challenges, such as the lack of efficient interface between NVs and photons, difficulty of maintaining spin coherence times, and scalable techniques for fabrication of NV-photon networks. This thesis focuses on overcoming these challenges by fabricating diamond devices to improve the collection efficiency of NV photon emission, especially from the zero phonon line (ZPL), while maintaining long spin coherence times after fabrication. After an introduction to the subject matter in Chapter 1, Chapter 2 discusses a fabrication technique to produce vertical membranes out of bulk diamond plates. This work showed that after reactive ion etching, the spin properties of isolated NVs in diamond nanostructures were largely preserved. We also observed increased photoluminescence collection from shallow implanted NV centers in these slabs. In Chapter 3, we describe a versatile nanofabrication method based on re-usable silicon membrane hard masks, patterned using standard lithography and mature silicon processing technology. These masks are transferred precisely onto targeted regions of diamond membranes, where photonic devices can be realized without the need for spin coating, wet etching or electron beam exposure. Chapter 4 describes and demonstrates an alternative technique for fabricating one-dimensional photonic crystal (PC) cavities in single-crystal diamond by a combination of reactive ion etching (RIE) and focused ion beam milling. We compare it to transferred silicon hard mask lithography with RIE. Chapter 5 demonstrate NV-nanocavity systems in the strong Purcell regime with consistently high Q factors while preserving the long spin coherence times of NVs. These systems enable coherent spin control of cavity-coupled semiconductor qubits with coherence times exceeding 200 [mu]s - an increase by two orders of magnitude over previously reported optical cavity-coupled solid-state qubits. Chapter 6 introduces a circular diamond "bullseye" grating that achieves the highest reported photon collection rate from a single NV center of 4.56 0.08 Mcps at saturation when fitted with the widely-used background counts subtraction method. We also quantified the emission by a g(²)-corrected saturation curve measurement which gives a rigorous single photon count rate of 2.7 ± 0.09 Mcps. By using dynamical decoupling sequences, we measured a spin coherence time of 1.7 ± 0.1 ms, which is comparable to the highest reported spin coherence times of NVs under ambient conditions and also indicates that the bullseye fabrication process does not degrade the spin properties noticeably. The planar architecture allows for on-chip integration, and the circular symmetry supports left- and right-handed circularly polarized light for spin-photon entanglement. In Chapter 7, we demonstrate a top-down fabrication process using a porous metal mask and a self-guiding RIE process that enables rapid nanocrystal creation across the entirety of a high-quality chemical vapor deposited (CVD) diamond substrate. High-purity CVD nanocrystals produced in this manner exhibit single NV phase coherence times reaching 210 ps and magnetic field sensitivities of 290 nT.Hz⁻¹/² without compromising the spatial resolution of a nanoscale probe.
by Luozhou Li.
Ph. D.
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Lemon, Christopher M. (Christopher Michael). "Supramolecular quantum dot-porphyrin assemblies for biological oxygen sensing." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79271.
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Thesis (S.M. in Inorganic Chemistry)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013.Vita. Cataloged from PDF version of thesis.
Includes bibliographical references.
Generating metabolic profiles of tumors provides a spatiotemporal map of the concentration of key species to assess and quantify tumor growth, metabolism, and response to therapy. Because the tumor microenvironment is characterized by hypoxia, the concentration of oxygen is an important indicator of tumor health. Understanding how this parameter changes as a function of disease progression is critical to develop novel targeted therapeutics. New non-invasive sensors must be developed that are small enough to penetrate into the tumor and monitor dynamic changes with high resolution. To this end, this thesis presents new oxygen sensors that are a supramolecular assemblies of a quantum dot (QD) and a palladium(II) porphyrin. High spectral overlap between QD emission and porphyrin absorption results in efficient Förster resonance energy transfer (FRET) for signal transduction in these sensors. Porphyrins with meso pyridyl substituents bind to the surface of the QD to produce self-assembled nanosensors. Since these macrocycles are sensitive in the 0-160 torr range, they are ideal phosphors for in vivo biological oxygen quantification. The QD serves as a two-photon antenna to enable sensing under two-photon excitation. Multiphoton imaging is a powerful technique that is nondestructive to tissue and provides high-resolution images of live tissue at depths of several hundred microns with submicron spatial resolution. Having studied the photohysical properties of these sensors under both one- and two-photon excitation in organic solvents, these sensors were then encapsulated in lipid micelles to quantify oxygen in aqueous media. In these constructs, the quantum dot also serves as an internal intensity standard, furnishing a ratiometric oxygen sensor. Preliminary in vivo multiphoton imaging and oxygen measurements were conducted using mice with chronic dorsal skinfold chambers or cranial windows. Together, the properties of this sensor establish a ratiometric two-photon oxygen sensor for applications in probing biological microenvironments.
by Christopher M. Lemon.
S.M.in Inorganic Chemistry
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Al-Galiby, Qusiy. "Quantum theory of sensing and thermoelectricity in molecular nanostructures." Thesis, Lancaster University, 2016. http://eprints.lancs.ac.uk/80279/.
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This thesis presents a series of studies into the electronic and thermoelectric properties of molecular junction single organic molecules: They include perylene Bisimide (PBIs), naphthalenediimide (NDI), metallo-porphryins and a large set of symmetric and asymmetric molecules. Two main techniques will be included in the theoretical approach, which are Density Functional Theory, which is implemented in the SIESTA code [1], and the Green’s function formalism of elctron transport (Chapter 2), which is implemented in the GOLLUM code [2], it is a next-generation code, born out of the non-equilibrium transport code SMEAGOL code [3]. Both techniques are used to extensively to study a family of perylene bisimide molecules (PBIs) (Chapter 3) to understand the potential of these molecules for label-free sensing of organic molecules by investigating a change in the electronic properties of PBI derivatives. Also, these techniques are used to simulate electrochemical gating of a single molecule naphthalenediimide (NDI) junction (Chapter 4) using a strategy to control the number of electrons on the molecule by modelling different forms of charge double layers comprising positive and negative ions. Chapter 5 will deal with the thermoelectric properties of the single organic molecule. I will demonstrate that varying the transition metal-centre of a porphyrin molecule over the family of metallic atoms allows the molecular energy levels to be tuned relative to the Fermi energy of the electrodes and that leads to the ability to tune the thermoelectric properties of metallo-porphryins. Chapter 6 will present our new approach to materials discovery for electronic and thermoelectric properties of single-molecule junctions. I will deal with a large set of symmetric and asymmetric molecules to demonstrate a general rule for molecular-scale quantum transport, which provides a new route to materials design and discovery. The rule of this approach that “the conductance of an asymmetric molecule is the geometric mean of the conductance of the two symmetric molecules derived from it and the thermopower of the asymmetric molecule is the algebraic mean of their thermopowers”.
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Sahand, Sina. "Microresonators and photonic crystals for quantum optics and sensing." College Park, Md. : University of Maryland, 2008. http://hdl.handle.net/1903/8345.
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Thesis (M.S.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Electrical and Computer Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Frey, Virginia. "Characterizing and mitigating temporally correlated noise processes in quantum systems." Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/21871.
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Quantum-enabled technologies promise advancements across a huge range of industrial, metrological and medical applications and are already demonstrating significant impacts, especially in the realm of sensing and metrology. While the extreme sensitivity of quantum systems to their environment is fueling those applications, it also represents a major hurdle to technologies which require long-term stability such as quantum computing and quantum simulations. In addition to the inherent decoherence phenomenon, the challenge associated with controlling a quantum system accurately and precisely, does in fact impede all of the aforementioned applications. Such techniques have therefore been subject to extensive research in both the academic and industrial sector and as a result, sophisticated quantum control techniques are emerging in order to understand, characterize and mitigate errors in quantum systems. This thesis presents how quantum control techniques can be employed to characterize and suppress both control imperfections and environmental noise in quantum systems, using experiments with trapped ions as a model quantum platform. We demonstrate two distinct but interrelated approaches that leverage either time-domain or frequency-domain information about the noise. In the first approach, we show how supervised learning algorithms can efficiently extract time-domain correlations from time-stamped sequences of projective measurements on a qubit. This information can then be used to perform real-time predictive control in which we autonomously pre-compensate anticipated qubit noise in order to stabilize the system. The second approach deploys provably optimal narrowband controls in order to characterize the specific spectral components of noise experienced by a qubit. Here, frequency-shifted Slepian functions permit reconstruction of system noise with maximum out-of-band rejection, and full spectrum reconstruction is enabled using techniques based on multitaper and Bayesian methods.
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Young, Carolyn. "Transport and charge sensing measurements of coupled quantum dot devices." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106374.
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We study transport and charge sensing measurements of double quantum dots (DQDs). Several proposals have been put forth for DQD-based qubits, making these systems interesting from the perspective of solid-state quantum computation. This thesis discusses three theoretical studies of error-generation in DQD qubit read-out. First, we consider transport measurements and calculate the contribution to the DQD conductance from cotunneling processes involving the virtual occupation of excited states. We present an efficient numerical method, based on the tight-binding formalism, for the calculation of the DQD transmission associated with two-particle cotunneling. We study the effect of electron-electron interactions within the constant interaction picture and, by treating the lead-DQD tunneling exactly, are able to consider the limit of strong coupling. We generate theoretical conductance maps, or stability diagrams, reflecting a wide region of parameter space, allowing us to compare the incidence of cotunneling in a variety of electrostatic regimes. Next, we focus on charge-sensing measurements and study the Heisenberg backaction associated with read out via a capacitively coupled quantum point contact (QPC). We show that the fundamental source of backaction is due to the QPC charge noise, rather than the shot noise. We derive a rigorous lower bound on the magnitude of the charge noise, and calculate the corresponding inelastic rates in a DQD charge qubit. Furthermore, we show that the charge and shot noise backaction mechanisms are in principle distinguishable when the QPC is non-adiabatic. We also apply our results to the case of two-electron DQD spin qubits, where the read out is performed via spin-to-charge conversion, and estimate the corresponding relaxation and dephasing times. Finally, we study an indirect backaction effect associated with read out by a QPC. In our picture, the QPC charge noise serves to locally heat a bath of phonons, driving it out of equilibrium. The phonons then travel to the DQD, where they are resonantly absorbed by the qubit, leading to inelastic transitions that show a distinct periodicity as a function of frequency. Strong oscillations in the DQD occupation have recently been measured experimentally by two independent groups. We show that the coupling between the phonon bath and the QPC can lead to focussing, which enhances the resonant phonon absorption and leads to the striking effect seen in experiment.Nous etudions la mesure de points quantiques doubles (DQDs), specifiquement le transport electronique et la detection de charge. Plusieurs propositions ont ete avancees pour des qubits bases sur les DQDs, qui rend ces systèmes interessants du point de vue du calcul quantique a l'etat solide. Cette these comprend trois etudes theoriques au sujet de la generation d'erreurs lors de la mesure des qubits DQD. Premierement, nous considerons les mesures de transport, et calculons la contribution a la conductance DQD des processus cotunneling impliquant l'occupation virtuelle des etats excites. Nous presentons une methode numerique efficace, basee sur le formalisme tight-binding, pour le calcul de la transmission DQD associee avec le cotunneling a deux electrons. Nous etudions l'effet des interactions electron-electron dans un modele d'interaction constante et, en traitant la puissance de tunnel entre les QDs exactement, examinons la limite de couplage fort. Nous generons des cartes de conductance theoriques qui refletent une vaste region de l'espace des parametres, et qui nous permettent de comparer l'incidence de cotunneling dans une variete de regimes electrostatiques. Ensuite, nous concentrons sur des mesures de detection de charge, et etudions le backaction Heisenberg associee a la mesure par un contact de point quantique (QPC). Nous montrons que la source fondamentale de backaction est du au bruit de charge du QPC, plutot que le bruit de courant. Nous formulons une borne inferieure rigoureuse pour l'ampleur du bruit de charge, et calculons les taux correspondants aux transitions inelastiques dans un qubit de charge DQD. Par ailleurs, nous montrons que les mecanismes de backaction associes avec le bruit de charge et de courrant, respectivement, peuvent en principe etre distingues quand le QPC est non-adiabatique. Nous appliquons egalement nos resultats au cas de qubits de spin, ou il y a deux electrons dans le DQD et la mesure est effectuee par la conversion entre spin et charge, et estimons les temps de relaxation et de decoherence correspondants.Finalement, nous etudions un effet backaction indirect associe a la lecture par un QPC. Dans notre modele, le bruit de charge du QPC sert a chauffer localement un bain de phonons, ce qui le conduit hors de l'equilibre. Ensuite, les phonons voyagent du QPC au DQD, ou ils sont absorbes de maniere resonante par le qubit, conduisant des transitions inelastiques. Ces transitions montrent une periodicite distincte en fonction de la frequence. De fortes oscillations dans l'occupation du DQD ont recemment ete mesurees experimentalement par deux groupes independants. Nous montrons que le couplage entre le bain de phonons et la charge du QPC peut conduire les phonons a concentrer, ce qui ameliore l'absorption de phonons resonants et produit l'effet vu au laboratoire.
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Foy, Christopher Ph D. (Christopher C. )Massachusetts Institute of Technology. "Solid-state spin-integrated circuits for quantum sensing and control." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127017.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 131-138).
Spin systems are an increasingly important quantum-sensing platform. In particular, atomic defect centers in diamond called nitrogen-vacancy (NV) centers offer impressive room temperature imaging capabilities for both magnetic fields and temperature. NV-based sensing platforms have found utility in solid-state physics, biological systems, and vector magnetometry. These applications highlight the immense promise of NV quantum sensors. Despite this promise, the use of NV centers within commercial devices remains limited to date, with many impediments to transitioning this platform from the laboratory. This thesis describes the development of solid-state spin-integrated circuits (S3IC) for quantum sensing and control with the overarching goal of creating scalable NV platforms. We present two major experiments that develop S3IC. These expand the application space of NV centers and improve device functionality. The first application was to develop an NV spin microscope capable of wide-field temperature and magnetic field imaging to elucidate functional device behavior at the microscopic scale. The second experiment was integrating the essential components of an NV spin microscope, spin control and detection, with integrated electronics. In this manner, S3IC combines the exceptional sensitivity of NV centers with the robustness and scalability of modern electronic chip-scale platforms. This co-integration of spin systems into integrated electronics shows a potential path for migrating previous proof-of-principal sensing demonstrations into affordable packages that demonstrate both much greater system integration and custom electronic architectures. In short, this work demonstrates advances in NV-ensemble quantum sensing platforms and establishes a foundation for future integration efforts, perhaps inspiring innovations in both application space and the development of new quantum devices.
by Christopher C. Foy.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Fisher, Melissa. "Optical sensing with CdSe quantum dots in condensed phase media." Tallahassee, Fla. : Florida State University, 2009. http://etd.lib.fsu.edu/theses/available/etd-11072009-112150/.
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Thesis (Ph. D.)--Florida State University, 2009.Advisor: Geoffrey F. Strouse, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Mar. 5, 2010). Document formatted into pages; contains xii, 157 pages. Includes bibliographical references.
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DE, ANGELIS ROBERTA. "Optical and chemical sensing investigation of InP surface quantum dots." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2012. http://hdl.handle.net/2108/202157.
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Photophysical properties of semiconductor quantum dots (QDs), such as broad absorption band and size dependent spectral emission, together with the high effective surface area available for interaction with target chemicals are attractive for applications like chem-/bio-sensors and lab-onchips. In the present work the state of the art of the research field will be discussed, with particular emphasis on the physical and chemical properties of near-infrared (NIR) emitting quantum dots. So far most of the reports of chem-/bio-sensing with QDs are based on colloidal nanocrystals synthesized by wet chemistry methods. Recently, a new approach has been introduced, which made use of Surface QDs (SQDs) grown by epitaxy on solid substrates. These QDs are not suitable to be used in solution, and thus cannot be exploited for application like in vivo imaging and diagnostics. However, the peculiarity that they are directly grown on a semiconductor surface represents a major advantage for chem-/bio-sensor and lab-on-chip design. At least in principle all is needed for a fluorescence based sensor is a light source, the quantum dots and a light detector, and all these components can be easily made with well-developed semiconductor fabrication technology. The presented research has given a contribute to this interesting new perspective. In particular this study is focused on InP SQDs. These island-like nanostructures were synthesized by gas source molecular beam epitaxy (GS-MBE) on In0.48Ga0.52P buffer layer lattice matched to Si doped GaAs substrate. They present a room-temperature NIR photoluminescence (PL). The emission wavelength depends on their dimensions (in the range 750-865 nm). For the present study samples presenting high dot coverage have been synthesized and characterized in term of structural, optical and chemical sensing properties. The most important achievement of this study has been the observation of a reversible PL enhancement when the SQDs were exposed to the vapours of different polar protic solvents. The emission energy and shape were not affected by the solvent vapours, while the photoluminescence intensity depends on solvent vapour concentration (with linear law over a limited concentration range). Besides, a clear correlation between the structural parameters of the SQDs and the response to chemicals has been identified. The presented results showed that InP SQDs are suitable materials for application like optical chemical sensors, bio-sensors and lab-onchip devices.
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Lee, Junghyun Ph D. Massachusetts Institute of Technology. "Dynamic and geometric control of electronic spins in diamond for quantum sensing and quantum information science." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119108.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 163-172).
In recent years, the nitrogen-vacancy (NV) color center in diamond, electronic spin defects embedded in a solid-state system, has emerged as a promising platform for quantum sensing and quantum information science in ambient temperature. Its capability of robust but high-precision spin control allows the NV center to be not only a useful atomic-scale magnetic field sensor but also an attractive building block for quantum processors. In this dissertation, I present novel schemes to dynamically and geometrically control NV spins for improved magnetic field sensing and studies of spin dynamics. First, dynamic NV phase control is synchronized with an external oscillating magnetic field, enabling single and ensemble NV AC magnetometry spectral resolution approaching sub-mHz. This protocol allows NV spins to sense an AC field spectral resolution beyond the inverse of NV spin lifetime. Also, dynamic control via dressed states of the NV spin is shown to provide effective tuning of the dipolar coupling between spins. In strongly interacting NV spin ensembles, this robust tool can be used to change the interaction dynamics. Second, geometric phase control is used to sense an external static magnetic field, improving detection sensitivity and field range. Especially, geometric phase magnetometry provides a 100-fold improvement of field range compared to conventional Ramsey magnetometry. Moreover, geometric phase control is used to observe the change of a topological state via measuring the Chern number, showing that an NV spin can serve as a tool for simple quantum simulations. Finally, I discuss the possibilities of combining the presented schemes with other quantum techniques to realize further interesting applications in future work.
by Junghyun Lee.
Ph. D.
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Chalopin, Thomas. "Quantum-enhanced sensing and synthetic Landau levels with ultracold dysprosium atoms Quantum-enhanced sensing using non-classical spin states of a highly magnetic atom Enhanced magnetic sensitivity with non-gaussian quantum fluctuations." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS589.
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Cette thèse porte sur des études expérimentales basées sur les interactions entre photons et atomes ultrafroids de dysprosium. La structure électronique du dysprosium est à l'origine de ses propriétés atomiques singulières, donnant accès à une phénoménologie physique diversifiée. Dans la première partie, nous donnons une description globale de notre expérience, et du protocole expérimental qui permet la production de gaz dégénérés de dysprosium bosonique. Une étape importante de notre séquence expérimentale porte sur l'utilisation de la raie d'intercombinaison à 626 nm pour le refroidissement Doppler d'atomes piégés. Nous montrons que la forte anisotropie de la polarisabilité de l'état excité est bénéfique pour le refroidissement évaporatif qui suit. Dans la deuxième partie, nous présentons des expériences qui utilisent le couplage entre les photons et le spin, inhérent à cette transition, pour manipuler les états internes des atomes et réaliser des états non-classiques de spin. Nous nous concentrons sur la réalisation d'états N00N, correspondant à la superposition d'états classiques ayant des aimantations opposées. Nous démontrons expérimentalement que la sensibilité aux champs magnétiques de ces états est proche de la limite de Heisenberg. La dernière partie est dédiée à l'effet Hall quantique, que nous étudions en encodant une dimension synthétique dans les états internes des atomes. Nous réalisons un système analogue aux niveaux de Landau à l'aide d'un couplage spin-orbite. Nous observons les propriétés du niveau de Landau fondamental : une dispersion supprimée, des états de bords chiraux, ainsi qu'une réponse de Hall caractéristique d'une topologie non-trivialeThis thesis presents several experimental studies based on light-spin interaction in ultracold gases of dysprosium. The complex electronic structure of dysprosium is at the origin of peculiar atomic properties, which can be used to explore a large variety of physical phenomena. In the first part, we give a global description of the apparatus, and of the experimental protocol that leads to the production of degenerate gases of bosonic dysprosium. A key step of our experimental sequence consists in using the intercombination line at 626 nm to perform in-trap Doppler cooling. We show in particular that the strong anisotropy of the excited state's polarizability is beneficial for the following evaporative cooling scheme. In the second part, we present experiments that use the strong light-spin coupling associated to this intercombination line to manipulate the internal states of the atoms and to realize non-classical spin states. We focus on the realization of N00N states, which are coherent superpositions of classical states with opposite magnetizations. We experimentally demonstrate that the magnetic field sensitivity of these states is close to the Heisenberg limit. The last part is dedicated to the study of quantum Hall physics, which we realize by encoding a synthetic dimension in the internal degree of freedom of the atoms. We show in particular that, using spin-orbit coupling, we realize a system that has the same structure as Landau levels. We probe paradigmatic properties of the lowest Landau level: suppressed dispersion in the bulk, chiral edge modes, cyclotron and skipping orbits, and a Hall response that is characteristic of a non-trivial topology
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Zhang, Haiyan. "Development of a novel, functional quantum dot-DNA/aptamer sensing technology." Thesis, University of Leeds, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.658610.
Full textAbstract:
Aptamers are short single-stranded DNA or RNA oligonucleotides artificially selected against specific targets. They exhibit high target binding affinity and exquisite specificity, making them very useful in developing biosensors for a wide range of targets, such as proteins, peptides, amino acids, drugs, metal ions and even whole cells. While fluorescent semiconductor nanocrystals, also known as quantum dots (QDs), have unique size-dependent, bright and extremely photo-stable fluorescence that make them as excellent fluorescent labels for biological imaging, sensing, cell tracking/trafficking and diagnostics. Their unique optical properties (broad absorption and narrow symmetric emission) are well-suited for FRET (fluorescence resonance energy transfer) based sensing applications. By combining the advance properties of both aptamers and QDs, this project aims to develop a sensitive, specific and robust aD-DNAlaptamer FRET based biosensing technology that can be used for rapid biosensing, diagnostics and environmental monitoring. A major hurdle here is the preparation of a compact, stable and water-soluble QD-bioconjugate that can effectively resist non-specific adsorption because FRET efficiency (E) decreases dramatically with the increasing donor-acceptor distance. Hence for high sensitivity, a compact QD-bioconjugate structure is essential. In this regard, a series of highly fluorescent, water-soluble CdSe/ZnS aDs were prepared first by ligand exchange with hydrophilic thiolated ligands, such as dihydrolipoic acid (DHLA), glutathione (GSH), dihydrolipoic acid-polyethyleneglycol (DHLAPEG600) derivatives. These QDs exhibited high fluorescence quantum yields (QYs, 6-30%), comparable to commercial water-soluble aDs (ca. 30%), but having significantly smaller hydrodynamic diameters «10 v.s. > 25 nm). Building upon these, three different QD-DNA aptamer sensing systems have been developed successfully: (1) A simple self-assembled aD-DNA system: I have found that thiolated DNA can self-assemble onto DHLA capped QDs to form compact, functional QD-DNA conjugates with small donor-acceptor distances, producing efficient FRET (E > 70%) at a relatively low (target: QD) copy number of 6:1. The resulting self-assembled aD-DNA (aptamer) conjugate has been used to detect low nM levels of labelled DNA target via QD sensitised dye FRET signal. Moreover, it has been successfully used for detection of nM level of a protein target via the encoded DNA aptamer sequence, although its specificity and stability still need further improvement. (2) A more stable and sensitive aD-dual-donor FRET sensing system based on an amine-modified DNA covalently coupled to a glutathione capped aD combined with the use of specific ethidium bromide (EB) intercalation in hybridized DNA duplex. As a result, both the aD and intercalated EBs can FRET to the dye acceptor appended to the complementary DNA, leading to significantly improved the overall FRET efficiency E, and hence sensitivity in both DNA and protein target detection down to pM level. (3) A Cu-free "clicked", robust, and_specific QD-DNA aptamer sensor. A compact, functional aD-DNA conjugate was prepared via the Cu-free "click chemistry" (CFCC) between a dihydrolipoic acid -polyethylene glycol-azide (DHLA-PEG600-N3) capped aD and a cyclooctyne modified DNA. The resulting QD-DNA conjugate is highly stable in biological buffer, effectively resisting nonspecific absorption, displaying a relatively small size (hydrodynamic radius - 5 nm) and retaining almost the native ay of the parent aD. Moreover, the CFCC based DNA conjugation method is also highly efficient, leading to high DNA loading (- 15-30 DNA strands per aD is readily achieved). This system is well-suited for robust biosensing: it can quantitate pM level of complementary DNA targets with SNP (singlenucleotide polymorphism) discrimination ability in complex media, e.g. 10% human serum. It can also detect pM level of a specific protein via the encoded DNA aptamer sequence. Compared with these approaches, the self-assembled system is the most convenient to prepare, but it has the least stability and cannot resist nonspecific absorption. The dual-donor FRET sensing system shows some enhancement on the stability and resisting nonspecific absorption, but it still cannot work in complex media, such as serum. The CFCC clicked QD-DNA aptamer sensor shows the highest stability, specificity and assay robustness, and can effectively work in clinical media. It can be readily extended to design sensors against other targets by simply clicking on specific aptamer sequences against such targets. Because the CFCC clicked QD-DNAlaptamer sensor shows high stability, specificity, robustness· and sensitivity, it may have a wide range of biosensing and diagnostic applications
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Ahmed, Imtiaz. "Radio-frequency capacitive gate-based sensing for silicon CMOS quantum electronics." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/284933.
Full textAbstract:
This thesis focuses on implementing radio frequency (rf) reflectometry techniques for dispersive detection of charge and spin dynamics in nanoscale devices. I have investigated three aspects of rf reflectometry using state-of-the-art silicon (Si) complementary metal-oxide-semiconductor (CMOS) nanowire field effect transistors (NWFETs). First, a high-sensitivity capacitive gate-based charge sensor is developed by optimising the external matching circuit to detect capacitive changes in the high frequency resonator. A new circuit topology is used where superconducting niobium nitride (NbN) inductor is connected in parallel with a single-gate Si NWFET resulting in resonators with loaded Q-factors in the 400-800 range. For a resonator operating at 330 MHz, I have achieved a charge sensitivity of 7.7 $\mu e/\sqrt{\text{Hz}}$ and, when operating at 616 MHz, I get 1.3 $\mu e/\sqrt{\text{Hz}}$. This gate-based sensor can be used for fast, accurate and scalable techniques for quantum state readout in Si CMOS based quantum computing. Second, this new circuit topology for the resonator is used with a dual-gate Si NWFET. This dual-gate device geometry provides access to a double quantum dot (DQD) system in few electron regime. The spin-state of the two-electron DQD system is detected dispersively using Pauli spin blockade between joint singlet S(2,0) and triplet T$_-$(1,1) states in a finite magnetic field $B$. The singlet-triplet relaxation time $T_1$ at $B=4.5$~T is measured to be $\sim$1 ms using standard homodyne detection technique. Third, I expand the range of applications of gate-based sensing to accurate temperature measurements. I have experimentally demonstrated a primary thermometer by embedding a single-gate Si NWFET with the rf capacitive gate-based sensor. The thermometer, termed as gate-based electron thermometer (GET), relies on cyclic electron tunneling between discrete energy levels of a quantum dot and a single electron reservoir in the NWFET. I have found that the full-width-half-maximum (FWHM) of the resonator phase response depends linearly with temperature via well known physical law by using the ratio $k_\text{B}/e$ between the Boltzmann constant and the electron charge. The GET is also found to be magnetic field independent like other primary thermometers such as Coulomb blockade and shot noise thermometers.
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Black, Paul Richie. "The application of quantum cascade lasers to mid-infrared gas sensing." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25739.
Full textAbstract:
This thesis explains the development of a quantum cascade laser based gas sensor and the verification of performance of the resulting product. The capability to detect trace levels of multiple species in varying physical conditions, specifically high temperature is shown. Optical designs capable of allowing the measurement technique to be used in a variety of applications have been developed, specifically multi-pass gas absorption cells. The accurate, precise and high speed analysis of the resulting data is made possible by spectral analysis algorithms. These developments and techniques were then applied to high temperature spectroscopic measurements. Spectra recorded at Rutherford Appleton Laboratory were used to calibrate high temperature measurements. The performance of the technology was thoroughly tested at the National Physical Laboratory. The resulting sensors have since been used to study the exhaust gases produced by a variety engine types ranging from cars to ships as well as atmospheric measurements.
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Fujisaku, Takahiro. "Development of quantum sensing methods using nitrogen－vacancy centers in diamonds." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263682.
Full text
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Cupps, Jay Fan Xudong. "Synthesis and application of semiconductor quantum dots in novel sensing applications." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/6101.
Full textAbstract:
The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract, appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on October 9, 2009) Thesis advisor: Dr. Xudong Fan. Includes bibliographical references.
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Schneider, Andre [Verfasser], and M. [Akademischer Betreuer] Weides. "Quantum Sensing Experiments with Superconducting Qubits / Andre Schneider ; Betreuer: M. Weides." Karlsruhe : KIT-Bibliothek, 2020. http://d-nb.info/1205807586/34.
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Lai, Khue Tian. "Optical characterisation of quantum well infrared photodetectors (QWIPs) for gas sensing applications." Thesis, University of Hull, 2004. http://hydra.hull.ac.uk/resources/hull:5592.
Full textAbstract:
Although much work has been done on λ∼5-12 μm quantum well infrared photodetectors (QvWPs), the distinctive feature of this project is the use of strain compensated materials on InP substrates, AIAs (tensile) and InGaAs (compressive), to achieve shorter wavelengths and higher temperature operation. Stepped wells, high thin barriers, and strained layers have been used to achieve λ∼2-5 μm and also enhanced normal incidence absorption. These structures also give an additional degree of freedom to control the position of the excited states in the QWIPs conduction band. The strain-balancing allows the use of Indium (In) concentrations up to 84% and hence deep wells with a large band offset relative to the outer barrier (which predominantly controls the dark current). The conduction band offset (ΔEc) for these structures (with respect to the wide InAlAs barrier) is estimated to be ∼675 meV. In the course of this work, we have also been able to estimate the subband nonparabolicity (m* and α) from absorption spectra in highly doped quantum wells (QWs). In this thesis, the main results which I present are on a comparative study of the intersubband absorption in a series of double barrier QW (DBQW) structures grown on GaAs substrates (Chapter 5) and InP substrates (Chapter 6). The background and theory of QWs is given in Chapter 1. In Chapter 2, the experimental procedure is detailed, while the theoretical model to calculate the conduction band profile and energy levels and the comparison of this model with literature values are presented in Chapter 3. Early results are discussed in Chapter 4. Finally, a summary and future work are outlined in Chapter 7.
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Lang, Jacob. "Dynamical decoupling based quantum sensing : Floquet analysis and finite-duration-pulse effects." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10057671/.
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A spin qubit can be protected from a dephasing spin bath using dynamical decoupling (DD). Microwave pi-pulses are repeatedly applied to the spin qubit to invert its state and average out any dephasing. Importantly, this protection fails when the DD pulse spacing is resonant with nuclear spins in the bath and characteristic dips appear in coherence traces forming the basis for nanoscale NMR and MRI. This emerging quantum technology has been demonstrated with the nitrogen vacancy center in diamond. Most DD protocols apply periodic repetitions of a basic pulse unit. This repetition motivates us to model the experiments using Floquet analysis. The characteristic coherence dips are found to be associated with avoided crossings in an underlying Floquet spectrum. The width and shape of these crossings determines the contrast and sharpness of the coherence dips. We derive analytic expressions for the coherence dips in terms of the Floquet quasienergies and Floquet modes. Typically, the DD microwave pulses are modelled as being instantaneous; however, real pulses have some finite duration and it was recently demonstrated that this pulse duration can cause extra dips to appear in coherence traces. We apply Floquet analysis to accurately model the complete system dynamics in the presence of these finite duration pulses and derive analytic expressions for the complete coherence response. We interpret the arrival of extra coherence dips as the opening of previously closed avoided crossings. We use this new understanding to propose protocols to exploit (for increased resolution) or suppress these extra coherence dips. Finally, we model the interplay between finite-duration-pulse effects and microwave detuning errors - an important problem as the detuning error is completely removed by instantaneous pulses so is not captured by most analytic models. We observe drastic effects including the splitting and suppression of the expected DD signal.
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Papatryfonos, Konstantinos. "1.6-2.5 μm long wavelength quantum dash based lasers for gas sensing." Thesis, Evry, Institut national des télécommunications, 2015. http://www.theses.fr/2015TELE0011/document.
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Ce travail de thèse a porté sur l’étude des propriétés fondamentales de bâtonnets quantiques InAs/InP formant la zone active de diodes lasers, à l’aide de microscopie et spectroscopie à effet tunnel à balayage. Nous avons pu étudier la nature de la dimensionnalité de ces nanostructures, mesurer la structure électronique de bâtonnets uniques en fonction de leur position dans la jonction PIN et également établir la cartographie de leur fonction d’onde à l’aide de mesures de conductivité différentielle. Nous avons de plus étudié le potentiel de ces bâtonnets quantiques comme milieu à gain de diodes lasers pour applications en détection de gaz. Nous avons optimisé des structures actives qui ont permis une émission laser en continu jusqu’à 2 µm et nos résultats expérimentaux et de modélisation montrent que cette longueur d’onde d’émission peut être étendue encore plus vers le MIR. De plus nous avons conçu et développé un procédé de fabrication de lasers DFB à couplage latéral à base de réseau de Bragg à fort rapport cyclique qui a permis d’améliorer de façon significative le coefficient de couplage (>40 cm-1). Ce procédé ne nécessitant pas de reprise d’épitaxie est très simple et à bas coût dans sa réalisation. Les valeurs élevées du coefficient de couplage sont d’autre part obtenues sans recourir à des réseaux de Bragg métalliques, comme c’est généralement le cas dans la littérature, qui introduisent des pertes de propagation non négligeables. Cette nouvelle approche a été mise en œuvre pour la réalisation d’un laser monofréquence émettant à 1,986 µm, avec une puissance de sortie par face de 4,5 mW, un courant de seuil de 65 mA et un taux de suppression des modes latéraux > 37 dB. Ces paramètres sont parfaitement adaptés à la détection e.g. de NH3, ce qui est très important pour des applications industrielles. Ce type de laser DFB à couplage latéral (LC-DFB), à fort k et faibles pertes de propagation constitue une brique de base pour la réalisation future de composants à deux sections présentant une gamme élevée d’accordabilité en continu pour des applications aussi bien en détection de gaz qu’en télécommunications optiquesDuring this work, we investigated the fundamental properties of single Qdashes, that were embedded in a diode-laser structure configuration, using cross-sectional scanning tunneling microscopy and spectroscopy. The main results included addressing the open question of the Qdash dimensionality nature, probing the electronic structure of individual nanostructures in respect to their precise location in the p-i-n junction and imaging of the Qdash electronic squared wavefunctions by high-stability differential conductivity mapping. In addition, we investigated Qdashes as the active material of semiconductor lasers, with special attention to the gas sensing application. We optimized Qdash based material at specific emission wavelengths above 1.55 um, and demonstrated CW lasing up to 2 um with high performances. Our experimental and simulation results show to be promising for further pushing the emission wavelength out, towards longer wavelengths in the future, using the same material system. Furthermore, a novel process has been developed, for the fabrication of laterally-coupled DFB lasers, based on high-duty-cycle etched Bragg gratings: The process provides appreciably improved coupling coefficients suitable for practical applications (~40 cm-1), while avoiding the complicated high cost processing steps, that had been employed in previous works (regrowth over corrugated substrates/ FIB lithography) and without using the conventional highly absorbing metal gratings, which introduce significant additional losses. We implemented this approach on our optimized epi-wafer and demonstrated high SMSR (>37dB) LC-DFB lasers emitting at 1.986 um, with an output power per facet up to 4.5 mW and Ith down to 65 mA for a 630 um cavity length, suitable for detection of the NH3 gas. These high-κ, low loss, preliminary results of our LC-DFB lasers, achieved using etched gratings, open the way for the fabrication of a two-section LC-DBR laser using the same technology in the future. Such a laser would combine a significantly simplified process, with sufficient feedback, continuous wide range tunability, and negligible grating-induced losses, finding potential applications both in sensing and telecommunications applications
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PERILLI, DANIELE. "Quantum Mechanical Modeling of Chemical Activated 2D-Materials for Electrocatalysis and Sensing." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2021. http://hdl.handle.net/10281/307660.
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I materiali bidimensionali hanno suscitato grande interesse da parte della comunità scientifica grazie alle loro eccezionali proprietà fisiche e le loro promettenti applicazioni in molti campi di interesse tecnologico. In particolare, negli ultimi anni, la frontiera della ricerca si è spostata dallo studio delle loro proprietà di base a sistemi 2D modificati chimicamente, quali materiali drogati, e alla loro interazione con altri sistemi, come nanoparticelle o superfici.
In questo contesto, le superfici metalliche sono spesso impiegate come catalizzatori eterogenei per la crescita mediante CVD di materiali 2D, sebbene il loro ruolo sia spesso relegato a mero materiale di supporto, con scarsa attenzione al potenziale che queste interfacce ibride offrono.
Questo lavoro di tesi presenta un’analisi di interfacce complesse tra materiali bidimensionali e superfici metalliche, sia dal punto della loro comprensione di base che alla loro applicazione in elettrocatalisi e nella sensoristica. In particolare, il lavoro è principalmente indirizzato alla comprensione del ruolo sinergico del substrato metallico sottostante e di difetti come vacanze o droganti sulle proprietà chimiche e fisiche dello strato bidimensionale supportato.
Metodi computazionali all'avanguardia sono stati impiegati per modellizzare sistemi quanto più realistici. Tutti i calcoli sono stati eseguiti attraverso la teoria del funzionale della densità (DFT), utilizzando funzionali corretti per le forze di dispersione.
L'idea principale di questo lavoro è quella di sfruttare l'elevata area superficiale che i materiali bidimensionali offrono per intrappolare oggetti quali atomi o cluster metallici. Tali oggetti possono essere usati come siti catalitici per molte reazioni di grande interesse o favorire l’interazione di questi sistemi con gas molecolari.Two-dimensional materials have aroused great interest among the scientific community thanks to their exceptional properties and promising applications in many technological fields. Nevertheless, over the last years, the frontline of research has moved from the study of basic properties of pure 2D crystals to chemical modified forms, i.e. doped 2D materials, and their interaction with other systems, such as nanoparticles, or surfaces. Within this frame, metal substrates are often employed as heterogeneous catalysts for the growth of 2D materials, although their role is often relegated to mere supporting materials, with a little attention to the potential that these hybrid interfaces (two-dimensional materials/metal surfaces) offer. This work investigates complex interfaces between two-dimensional materials and metal surfaces, both from the point of view of basic understanding of such systems and application in electrocatalysis and sensing. In particular, the thesis is mainly addressed to the understanding of the synergistic role of the underlying metal substrate and defects like vacancies or dopants on the chemical and physical properties of the two-dimensional adlayer. We employed state-of-the-art computational methods to model systems that are as realistic as possible. All calculations have been performed through density functional theory (DFT), using dispersion-corrected functionals. The main idea of this work is to exploit the high surface area of two-dimensional materials to trap objects that can be atoms or metal clusters, as well as molecules. Such objects can be used as catalytic sites for many reactions of great interest or induce some modification in the 2D material, making it suitable as a sensor.
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Wang, Shujun. "Synthesis of Graphene Quantum Dots and Their Applications in Sensing and Light Harvesting." Thesis, Griffith University, 2017. http://hdl.handle.net/10072/366102.
Full textAbstract:
Graphene quantum dot (GQD) is a derivative of 2D material graphene. It normally refers to small fragments of graphene having lateral size below 100nm. Not only do GQDs inherit some of the wonder properties of bulk graphene, but they possess properties unique from bulk graphene due to the quantum confinement and edge effects. As an emerging material, GQDs presents a new open field for broad
investigations, from synthesis, explanation of properties to promising applications including sensing, bio-imaging, nanomedicine (e. g. drug delivery), energy conversion (e. g. photovoltaic devices and photocatalyst) optoelectronics, spintronics etc. This PhD project is dedicated to three correlated aspects of GQDs: 1) development of new methods for synthesis of GQDs; 2) mechanistic studies of the
photoluminescence (PL) possessed by GQDs, and; 3) the applications of GQDs in sensing and light harvesting.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
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BRUNI, FRANCESCO. "NOVEL MATERIAL DESIGN AND MANIPULATION STRATEGIES FOR ADVANCED OPTOELECTRONIC APPLICATIONS." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2017. http://hdl.handle.net/10281/151660.
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Il mio progetto di dottorato è stato focalizzato sui semiconduttori organici per applicazioni fotovoltaiche e di fotorivelazione. Inizialmente ho lavorato sul controllo morfologico di blende binarie di molecole organiche e fullereni usando la cosiddetta strategia dei pigmenti latenti. In particolare ho lavorato sull'ingenierizzazione dello strato attivo di celle solari organiche a eterogiunzione. Ho dimostrato una nuova strategia per controllare la segregazione di fase in film sottili di molecole elettron donatrici e fullereni, introducendo nel sistema un network di legami di idrogeno attivato termicamente. Successivamente ho studiato i processi di accumulazione di carica all’interfaccia tra acqua e un semiconduttore polimerico per applicazioni biomediche per mezzo di nanocristalli colloidali biemissivi con alta sensibilità verso agenti elettronattrattori. In fine, ho dedicato l’ultima parte del mio lavoro all’approfondimento delle possibili applicazioni di questa classe di nanocristalli come sensori raziometrici di pH intracellulare e come vernici per il monitoraggio ottico della pressione.My PhD has been focused on organic semiconductors for photovoltaics and photodetecting applications. Initially, I worked on the control of the morphology in binary blends of small organic molecules and fullerenes using the so called latent pigment approach. Subsequently, I investigated the charge accumulation and polarization effect occurring at the interface between water and a polymeric semiconductor used as optical component in retinal prosthesis by means of inorganic colloidal nanocrystals featuring a ratiometric sensing ability for electron withdrawing agents. As a last part of the work, I focalized on the applications of these nanocrystals as ratiometric sensors for intracellular pH probing and pressure optical monitoring. Specifically, during the first part of my PhD, I worked in the field of organic photovoltaics on the morphology engineering of the active layer of small molecules bulk-heterojunction solar cells. I demonstrated a new strategy to fine tune the phase-segregation in thin films of a suitably functionalized electron donor blended with fullerene derivatives by introducing in the system a post-deposition thermally activated network of hydrogen bonds that leads to improved stability and high crystallinity. Moreover, this process increases the carrier mobility of the donor species and allows for controlling the size of segregated domains resulting in an improved efficiency of the photovoltaic devices. This work revealed the great potential of the latent hydrogen bonding strategy that I subsequently exploited to fabricate nanometric semiconductive features on the film surface by using a very simple maskless lithographic technique. To do so, I focalized a UV laser into a confocal microscope and used the objective as a “brush” to thermically induce a localized hydrogen bonding driven crystallization with diffraction limited resolution. My work on organic semiconductors continued with a study on the surface polarization driven charge separation at the P3HT/water interfaces in optoelectronic devices for biologic applications. In this work, I probed the local accumulation of positive charges on the P3HT surface in aqueous environment by exploiting the ratiometric sensing capabilities of particular engineered core/shell heterostuctures called dot-in-bulk nanocrystals (DiB-NCs). These structures feature two-colour emission due to the simultaneous recombination of their core and shell localized excitons. Importantly, the two emissions are differently affected by the external chemical environment, making DiB-NCs ideal optical ratiometric sensors. In the second part of my PhD, I, therefore, focalized on the single particle sensing application of DiB-NCs. Specifically, I used them to ratiometrically probe intracellular pH in living cells. With this aim, I studied their ratiometric response in solution by titration with an acid and a base. Subsequently, I internalized them into living human embryonic kidney (HEK) cells and monitored an externally induced alteration of the intracellular pH. Importantly, viability test on DiB-NCs revealed no cytotoxicity demonstrating their great potential as ratiometric pH probes for biologic application. Finally, I used DiB-NCs as a proof-of-concept single particle ratiometric pressure sensitive paint (r-PSP). In this application, the emission ratio between the core and the shell emission is used to determine the oxygen partial pressure and therefore the atmospheric pressure of the NC environment.
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Albahrani, Sayed Mohamed Baqer. "Photoluminescent CdSe/CdS/ZnS quantum dots for temperature and pressure sensing in elastohydrodynamic." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI016/document.
Full textAbstract:
La température et la pression sont deux paramètres particulièrement importants pour l’optimisation des performances du régime de lubrification élastohydrodynamique (EHL). A ce jour, différentes méthodes expérimentales ont été développées, avec plus ou moins du succès, pour la mesure de ces deux paramètres. Ce travail présente, en continuité de ces approches, des investigations visant à développer une nouvelle technique in situ permettant de mesurer localement ces deux grandeurs dans les contacts élastohydrodynamiques (EHD). Cette technique exploite la sensibilité en photoluminescence (PL) des boîtes quantiques (ou en anglais « quantum dots (QDs)) de CdSe/CdS/ZnS aux variations de température et de pression. A cet égard, des calibrations ont été réalisées afin d’évaluer la sensibilité de ces QDs aux deux paramètres. De plus, la versatilité de ces QDs comme nanosondes a été examinée en testant deux lubrifiants différents : le squalane et un mélange de squalane et de cyclopentane. Des mesures ont été également effectuées sous conditions dynamiques afin d’étudier (i) l’influence de la présence des QDs sur la rhéologie du lubrifiant et (ii) l’influence du taux de cisaillement sur la PL des QDs. Bien que ces différents tests aient prouvé le potentiel des QDs de CdSe/CdS/ZnS, ils ont révélé l’existence d’autres paramètres qui peuvent, tout comme la température et la pression, en modifier la réponse. L’étude a été menée afin d’approfondir la compréhension des mécanismes responsables de tels effets. Plus important encore, une méthodologie a été définie pour minimiser ces effets indésirables, et pour in fine, permettre l’usage de ces QDs en tant que nanosondes fiablesTemperature and pressure are two relevant parameters for the optimization of lubrication performance in the elastohydrodynamic lubrication (EHL) regime. To date, various experimental methods have been developed to measure these two parameters with more or less success. In a continuation of these efforts, some investigations are presented in the current work in view of developing a new in situ technique allowing for local measurements of these two parameters throughout elastohydrodynamic (EHD) contacts. This technique exploits the photoluminescence (PL) sensitivity of CdSe/CdS/ZnS quantum dots (QDs) to changes in temperature and pressure. In this respect, calibrations have been carried out in order to establish the sensitivity of these QDs to the two parameters. Moreover, the versatility of these QDs for sensing applications have been examined by testing two different lubricants, namely squalane and a mixture of squalane and cyclopentane. Some measurements were also conducted under dynamic conditions, in order to study (i) the influence of the QDs presence on the lubricant rheology and (ii) the influence of shear rate on the PL of QDs. Although these different tests demonstrated the potential of CdSe/CdS/ZnS QDs, they revealed the existence of other parameters that affect, in addition to temperature and pressure, their response. A comprehensive study was thus conducted in order to elucidate the mechanisms behind these findings. More importantly, a methodology was defined in order to minimize these undesired influences and, in fine, enable these QDs to be used as reliable nanosensors
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Basso, Luca. "Laser-synthesis and optical functionalization of NV-fluorescent nanodiamonds for quantum sensing applications." Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/250439.
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The absence of a cheap and easily scalable synthesis technique for nitrogen-vacancy (NV) centers enriched nanodiamonds (NDs) is a critical factor for the development of devices based on this very peculiar nanoparticle. Indeed, the combination between the unique NV fluorescence properties and NDs characteristics allow to obtain a tool having quantum sensing capabilities, with nanometric spatial resolution, which is able to operate in a wide range of temperature, pressures and in harsh chemical conditions. NVenriched NDs applications in nanothermometry, nanomagnetometry and in bio-imaging have already been reported. However, most of the standard fluorescent NDs production techniques present common drawbacks: poor control in NDs size distribution and in nitrogen concentration, as well as the need of post-synthesis process to clean the NDs surface from impurities and to increase the NV density. In this thesis, an alternative method for fluorescent NDs synthesis based on pulsed laser ablation (PLA) of graphite is demonstrated. After the introductory chapters on NV-centers physics and NDs properties (Chapter 2 and 3), the demonstration that PLA is a viable route for synthesis of NDs is given in Chapter 4. In particular, PLA of graphite and of diamond-like carbon is performed in water. Here, a thermodynamic model taking into account the peculiar physical processes occurring during PLA is developed to explain NDs formation. Then, synthesis of NV-enriched NDs is demonstrated through PLA of graphite in a nitrogen atmosphere (Chapter 5) and in liquid nitrogen (Chapter 6). In both chapters, the thermodynamic model is adapted to explain diamond phase formation in a gaseous environment and in a cryogenic liquid. Furthermore, NV centers optical properties are fully characterized with optically detected magnetic resonance (ODMR) spectroscopy. Finally, in Chapter 7, fluorescent NDs are produced by laser ablation of N-doped graphite in water. This particular target is then used for a quantitative comparison between the other fluorescent NDs laser-synthesis, with the aim of establishing in which condition the highest NV-center formation efficiency is achieved.
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Freire, Rafael Melo. "Magnetic Nanoparticles and Carbon Quantum Dots: Interdisciplinary Nanoparticles for Sensing and/or Education." reponame:Repositório Institucional da UFC, 2016. http://www.repositorio.ufc.br/handle/riufc/22447.
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FREIRE, Rafael Melo. Magnetic nanoparticles and carbon quantum dots: interdisciplinary nanoparticles for sensing and/or education. 182 f. 2016. Tese (Doutorado em Química)-Universidade Federal do Ceará, Fortaleza, 2016.Submitted by Jairo Viana (jairo@ufc.br) on 2017-04-04T18:36:04Z No. of bitstreams: 1 2016_tese_rmfreire.pdf: 11804231 bytes, checksum: 1a676a521f06fad619e4adfb61cc2a45 (MD5)
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In this work, a sensing strategy for detection and identification of proteins with magnetic nanoparticles (MNPs) and carbon quantum dots (CQDs) was developed. In this sense, mixed ferrites of general formula M0.5Zn0.5Fe2O4 (M=Mn or Ni) were first investigated. Therefore, the hydro/solvothermal synthesis of these magnetic nanoparticles was performed under different conditions (solvent, reaction time and base concentration). Based on the magnetic properties of the two MNPs investigated, the mixed ferrite of formula Mn0.5Zn0.5Fe2O4 (MnZn) synthesized using water showed the greatest potential for sensing. Since among all synthesized MNPs, this sample displayed the highest saturation magnetization value ( M S 50 emu/g), lower crystallite size around 12 nm and superparamagnetic behavior. Once the first part of the doctoral thesis was concluded, the next step was to find a fluorescence probe. In this regard, it was performed the synthesis, as well as the application of branched poliethylenimine-functionalized carbon quantum dots (CQDs.BPEI). These new carbon-based nanoparticles were found to be protein-responsive. Since CQDs.BPEI were able to detect eight different proteins (four metallic and four non-metallic) even using concentrations in the range of 5 – 40 nM. Fluorescence titrations performed at 298 and 310 K displayed the fluorescence quenching through collisional mechanism. Therefore, it was also possible to conclude that the fluorescence quench comes from the amino acid residues on the surface of the proteins. To further check the potential of the CQDs.BPEI, it was developed a “nose” based methodology to identify proteins. Using materials as cheap as Cu2+ and ethylenediaminetetraacetic acid, the chemical “nose” approach was able to discriminate six different proteins at 40 nM concentration in phosphate buffered saline (PBS, pH 7.4). The identification accuracy of the random unknown set was 90% with all misclassification occurring for albumin proteins (e.g., Bovine Serum Albumin and Human Serum Albumin). The displayed results evidence the great potential of CQDs.BPEI as a protein-responsive probe to detect and identify proteins. Taken together, MnZn and CQDs.BPEI were capable to build up a powerful protein sensing approach. In addition, realizing the great potential of CQDs in the educational field, it was also developed and successfully applied (for more than 70 students from biotechnology, pharmacy, engineers and geology courses) a lab experiment to demonstrate lightrelated quantum phenomena.
Neste trabalho, uma estratégia para detecção e identificação de proteínas incluindo nanopartículas magnéticas (MNPs) e pontos quânticos de carbono (CQDs) foi desenvolvida. Assim, ferritas mistas de fórmula M0.5Zn0.5Fe2O4 (M=Mn or Ni) foram inicialmente investigadas. Neste sentido, suas sínteses foram feitas utilizando diferentes condições (solvente, tempo reacional e concentração de base). Logo, baseado nas propriedades magnéticas das MNPs sintetizadas, escolheu-se a Mn0.5Zn0.5Fe2O4 (MnZn) sintetizada em água por mostrar grande potencial, uma vez que essa amostra apresentou alto valor de magnetização de saturação ( M S 50 emu/g) em comparação com outras ferritas de composição semelhante, baixo tamanho de cristalito por volta de 12 nm e comportamento superparamagnético. Com a primeira parte do trabalho concluída, a próxima etapa foi encontrar uma sonda fluorescente. Assim, realizou-se a síntese dos CQDs funcionalizados com grupamentos amina (CQDs.BPEI). Quando testada contra 8 diferentes proteínas (4 metálicas e 4 não-metálicas), apresentou variação da emissão para concentrações na faixa de 5 – 40 nM. Titulações fluorescentes também foram realizadas e observou-se que a supressão da fluorescência ocorre via mecanismo colisional a partir de resíduos aminoácidos na superfície da proteína. Para adicionalmente checar o potencial dos CQDs.BPEI, foi desenvolvida abordagem para identificar proteínas utilizando materiais Cu2+ e o ácido etilenodiamino tetraacético. No total, a estratégia desenvolvida foi capaz de identificar corretamente 6 diferentes proteínas a 40 nM. A precisão da identificação encontrada foi 90% para as amostras desconhecidas. Contudo, vale ressaltar que os 10% de engano foram apenas entre BSA e HSA, duas proteínas albumínicas muito similares. Os resultados obtidos nessa parte do trabalho evidenciam o alto potencial de CQDs.BPEI para detecção e identificação de proteínas. Observando os resultados do trabalho como um todo, pode-se afirmar que MnZn e CQDs.BPEI são capazes de compor excelente abordagem para detecção e identificação de proteínas. Adicionalmente, foi explorada a utilidade dos CQDs para o campo educacional. Dessa forma, foi também desenvolvido e aplicado (mais de 70 estudantes de graduação oriundos dos cursos de biotecnologia, farmácia, engenharias e geologia) um experimento de laboratório para demonstrar fenômenos quânticos relacionados com a luz.
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Lu, Kyle Benjamin. "Microwave Instrumentation and Sensing Techniques for Quantum Efficiency and Minority-Carrier Lifetime Measurements." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3503.
Full textAbstract:
A non-contact method characterizing the quantum efficiency of a solar cell using the microwave reflectance signature is presented in this thesis. Traditional solar cell quantum efficiency (QE) measurements are only possible near the completion of the fabrication process using contacts in direct physical connection with the metalized surface tabs to probe and extract charge carriers from the device. However, pressure within the solar metrology industry to report the spectral performance of the device earlier in the manufacturing process as part of the process control loop requires that a new non-contact method be developed. This thesis work contributes the development of a non-contact focused microwave reflectance technique capable of acquiring the full 365nm - 1100nm spectrum in under 1 minute. Unlike many similar Time Resolved Microwave Conductivity (TRMC) and Microwave Photoconductivity Decay (µPCD) systems based on the open-ended waveguide technique, this measurement is developed to perform measurements in the far-field. As such, a different mechanism for understanding the problem is presented using the modulated scatterer concept from antenna theory. Using a combination of high dielectric sensor pads and negative-index of refraction microwave lenses, we are able to tune the far-field field probe size from 5mm-150mm allowing for high speed single point in-line measurements or high spatial sensitivity laboratory measurements.
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Blums, Valdis. "Diffractive Optics for Sensing and Networking with Trapped Ions." Thesis, Griffith University, 2021. http://hdl.handle.net/10072/401639.
Full textAbstract:
In this thesis I present my contribution towards a quantum communication platform using trapped ions, Fresnel optics, and frequency conversion waveguides. I discuss the major components required for this platform, as well as show our high control over trapped ions. I also demonstrate that the high resolution imaging of lens-based optical interconnects enable a new way to monitor trapped ions as 3D sub-attonewton force sensors. The experiments presented here were achieved across two Yb+ ion traps.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
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Pang, Shuo. "Whispering gallery modes in quantum dot-embedded dielectric microspheres for tagless remote refractometric sensing." Texas A&M University, 2008. http://hdl.handle.net/1969.1/85998.
Full textAbstract:
This thesis presents the development of a refractometric sensor based on
quantum dot-embedded polystyrene microspheres. The technique uses optical
resonances within a microsphere, known as Whispering-Gallery Modes (WGMs), which
produce narrow spectral peaks. The basic theory of WGMs is reviewed and specifically
discussed for biosensing application.
The spectral shifts of WGM peaks are sensitive to changes in the local refractive
index. In the experiments, two-photon excited luminescence from the quantum dots
couples into several WGMs within the microresonator. By optimizing the detection area,
the spectral visibility of the WGMs is improved. The spectral shifts are measured as the
surrounding index of refraction changes. The experimental sensitivity is about five times
greater than that predicted by Mie theory.
The sensor element is based on commercially available dielectric microspheres
with a diameter about 10 μm. Thus, the technique is more economic and suitable for
sensing applications, compared to microspheres of 100 μm in size which can only be
made in the laboratory.
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Hagelin, Alexander. "ZnO nanoparticles : synthesis of Ga-doped ZnO, oxygen gas sensing and quantum chemical investigation." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-64730.
Full textAbstract:
Doped ZnO nanoparticles were synthesized by three different methods – electrochemical deposition under oxidizing conditions (EDOC) , combustion method and wet chemical synthesis – for investigating the oxygen gas sensing response. Ga-doped ZnO was mostly synthesized but also In-doped ZnO was made. The samples were analyzed by XRD, SEM, EDX and TEM. Gas response curves are given alongside with Langmuir fitted curves and data for pure ZnO and Ga-doped ZnO. DFT quantum chemical investigation of cluster models ZnO nanoparticles were performed to evaluate defect effects and oxygen and nitrogen dioxide reactions with the ZnO surface. Defects were investigated by DOS and HOMO-LUMO plots , and are oxygen vacancy, zinc vacancy, zinc interstitial and gallium doping by replacing zinc with gallium. Oxygen and nitrogen dioxide reactions were investigated by computing Mulliken charges, bond lengths, DOS spectra and HOMO-LUMO plots.
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Schönfeld, Rolf Simon [Verfasser]. "Optical readout of single spins for quantum computing and magnetic sensing / Rolf Simon Schönfeld." Berlin : Freie Universität Berlin, 2011. http://d-nb.info/1029936900/34.
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Chen, Edward H. (Edward Hong). "Coherent control of nitrogen-vacancy centers in diamond nanostructures for quantum sensing and networking." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107324.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 99-123).
The exceptional optical and spin properties of the negatively charged nitrogen-vacancy (NV-) center in diamond have led to numerous applications ranging from super-resolution imaging to the exploration of previously untested new phenomena using quantum entanglement for information processing and sensing. The solid-state environment of the diamond allows us to engineer nanostructures, which are promising for enhancing the optical and spin properties of the NV-. To help develop a component needed for a diamond-based quantum network, we recently achieved coherent electron spin control of long-lived NV-s in diamond nanostructures using a transferrable hard-mask for both etching and ion implantation. We also developed a super-resolution imaging technique for characterizing such systems, and we furthermore demonstrate high-sensitivity electrometry using a large number of NV-s. However, it remains an open area of investigation whether certain nano-fabrication processes for patterning nanostructures into diamond cause irrecoverable damage or introduce atomic impurities to the crystal that would lead to a significant degradation of the NV- properties. Another remaining challenge is to produce fault-tolerant multi-qubit registers within nanostructures for improved robustness and scalability for use in compact quantum sensors or quantum networks. By building on the results in this thesis, it may be possible to design nanostructures for enhancing initialization, control and read-out fidelities of defect-based solid-state quantum technologies.
by Edward H. Chen.
Ph. D.
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Adegoke, Oluwasesan. "The design of quantum dots and their conjugates as luminescent probes for analyte sensing." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1010866.
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The design and applications of quantum dots (QDs) as fluorescent probes for analyte sensing is presented. Cadmium based thiol-capped QDs were employed as probe for the detection of analytes. Comparative studies between core CdTe and core-shell CdTe@ZnS QDs showed that the overall sensitivity and selectivity of the sensor was dependent on the nature of the capping agent and the QDs employed, hence making CdTe@ZnS QDs a more superior sensor than the core. To explore the luminescent sensing of QDs based on the fluorescence “turn ON” mode, L-glutathione-capped CdTe QDs was conjugated to 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT) to form a QDs-4AT conjugate system. The QDs-4AT nanoprobe was highly selective and sensitive to the detection of bromide ion with a very low limit of detection. Subsequently, metallo-phthalocyanines (MPcs) were employed as host molecules on the surface of QDs based on the covalent linking of the QDs to the MPc. Elucidation of the reaction mechanism showed that the fluorescence “turn ON” effect of the QDs-MPc probe in the presence of the analyte was due to axial ligation of the analytes to the Pc ring. Studies showed that the type of substituent attached to the MPc ring influenced the overall sensitivity of the probe. Additionally, a comparative investigation using newly synthesized phthalocyanine and triaza-benzcorrole complexes was conducted when these complexes were conjugated to CdSe@ZnS QDs for analyte sensing. Results showed that the triaza-benzcorrole complex can be employed as a host-molecule sensor but displayed a lower sensitivity for analyte sensing in comparison to the phthalocyanine complex.
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Lu, Qi. "Mid-infrared antimonide based type II quantum dot lasers for use in gas sensing." Thesis, Lancaster University, 2015. http://eprints.lancs.ac.uk/74442/.
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Type II InSb/InAs quantum dots (QDs) emitting in the 3-4 µm range are promising candidate as the gain medium for semiconductor laser diodes. The molecular beam epitaxy (MBE) growth of the QDs on GaAs and InP substrates can largely cut down the costs for future devices and massively broaden its application possibilities using the more mature material platforms. Different metamorphic growth techniques including inter-facial misfit (IMF) arrays were experimented for the integration of the InSb QDs on GaAs substrates. The density of threading dislocations and the quality of the QDs were investigated using cross-sectional transmission electron microscopy (TEM) images, high resolution X-ray diffraction (XRD) and photo-luminescence (PL). The 4 K PL intensity and linewidth of InSb QDs grown onto a 3 μm thick InAs buffer layer directly deposited onto GaAs proved to be superior to that from QDs grown on 0.5 μm thick InAs buffer layers using either AlSb or GaSb interlayers with IMF technique. Even though the dislocation densities are still high in all the 3 samples (~109 cm-2), they all achieved comparable PL intensity as the QDs grown on InAs substrates. Electro-luminescence (EL) from the QDs on GaAs substrates were obtained up to 180 K, which was the first step towards making mid-infrared InSb QD light sources on GaAs. From the study of PL temperature quenching, thermal excitation of holes out of the QDs was identified as one of the major reasons for weaker PL/EL signals at higher temperature range. To compensate the thermal leakage problem, the QDs integrated on InP substrates were grown between InGaAs barriers, which can provide a larger valence band offset compared with InAs. The QD PL peak moved to shorter wavelength (~2.7 μm) partly due to the stronger confinement, and the PL quenching was significantly slower for T > 100 K. From microscopy images, PL characteristics and calculations, the size and composition of the QDs were estimated. The InSb QD laser structures on InAs substrates emitting at around 3.1 µm were improved by using liquid phase epitaxy (LPE) grown InAsSbP p-cladding layers and two step InAs n-cladding layers. The maximum working temperature was increased from 60 K to 120 K. The gain was determined to be 2.9 cm-1 per QD layer and the waveguide loss was around 15 cm-1 at 4 K. The emission wavelength of these lasers showed first a blue shift followed by a red shift with increasing temperature, identical with the PL characteristics. Multimodal spectra were measured using Fourier transform infrared spectroscopy (FTIR). Spontaneous emission measurements below threshold revealed a blue shift of the peak wavelength with increasing current, which was caused by the charging effect in the QDs. The characteristic temperature, T0 = 101K below 50 K, but decreased to 48K at higher temperatures. Current leakage from the active region into the cladding layers was possibly the main reason for the increase of threshold current and decay of T0 with rising temperature.
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Seoudi, Tarek. "Non-intrusive CdSe-based quantum dots for sensing pressure and temperature in lubricated contacts." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI009.
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Cette thèse est dédiée à la mesure des pressions et des températures locales et à la comparaison de la génération de chaleur dans les contacts élastohydrodynamiques (EHD) de type tout acier et hybride (nitrure de silicium-acier). Le but ultime de ce travail est de développer une nouvelle technique in situ non-intrusive, exploitant la sensibilité de la photoluminescence (PL) des boîtes quantiques (QDs) de CdSe/CdS/ZnS aux variations de pression et température, afin de cartographier ces deux paramètres dans les contacts EHD. Dispersible à faible concentration dans les lubrifiants, il est montré que les QDs ne modifient pas le comportement rhéologique du fluide porteur et que le cisaillement n’est pas perturbateur à la réponse en PL. La calibration des QDs en suspension confirme la dépendance de la réponse en PL des QDs à la pression et à la température. Les mesures in situ sont effectuées en utilisant un banc d’essai bille-disque. La comparaison entre les mesures in situ de pression et de température et celles prédites à l'aide d'un modèle éléments finis TEHD interne montre une bonne concordance, ce qui démontre la faisabilité de la méthodologie proposée. Les effets du glissement et du chargement normal sur la pression, la température et la chaleur générée sont reportés. L’effet des propriétés thermiques des solides est souligné et la répartition de la chaleur générée entre les solides en contact est étudiée. L'équilibre énergétique entre l'énergie mécanique et l'énergie thermique interne générée par compression et cisaillement est démontré en comparant les pertes de puissance expérimentales et la chaleur générée issue du modèle numérique, pour des contacts acier-acier et hybridesThis thesis is dedicated to the measurement of local pressure and temperature and to compare the heat generation in all-steel and silicon nitride-steel (hybrid) elastohydrodynamic (EHD) contacts. The ultimate goal of this work is to develop a new non-intrusive in situ technique, exploiting the sensitivity of the photoluminescence (PL) of CdSe/CdS/ZnS quantum dots (QDs) to pressure and temperature. Dispersible in small concentration in lubricants, it is shown that the QDs doesn’t modify the rheological behavior of the carrier fluid and that shearing is not perturbative to the QDs PL response. The calibration of QDs in the suspension confirms the QDs PL dependence on temperature and pressure. The in situ measurements were conducted in EHD contacts using a ball-on-disc test rig. Comparisons between pressure and temperature measurements and predictions, using an in–house finite element thermal EHD model, showed a good agreement which demonstrates the feasibility of the proposed methodology. The effects of sliding and normal loading on pressure, temperature and heat generation are indicated. The effect of the thermal properties of the solid materials is underlined and the partition of the generated heat between the contacting solids is investigated. The energy equilibrium between the mechanical energy and the internal thermal energy generated by compression and shearing is demonstrated by comparing experimental power losses and numerical heat generation, in steel-steel and hybrid contacts
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Schneider, Andre [Verfasser], Martin P. [Akademischer Betreuer] Weides, and Alexey V. [Akademischer Betreuer] Ustinov. "Quantum Sensing Experiments with Superconducting Qubits / Andre Schneider ; Martin P. Weides, Alexey V. Ustinov." Karlsruhe : KIT Scientific Publishing, 2021. http://d-nb.info/1234149923/34.
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