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1
Pingault, Benjamin Jean-Pierre. "The silicon-vacancy centre in diamond for quantum information processing." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/269366.
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Atomic defects in solids offer access to atom-like quantum properties without complex trapping methods while displaying a rich physics due to interactions with their solid-state environment. Such properties have made them an advantageous building block for quantum information processing, in particular to construct a quantum network, where information would be encoded in spins and transferred between nodes through photons. Among defects in solids, the negatively charged silicon-vacancy centre in diamond (SiV$^{−}$) has attracted attention for its very promising optical properties for such a network. In this thesis, we investigate the spin properties of the silicon-vacancy centre as a potential spin-photon interface. First, we use resonant excitation of an SiV$^{−}$ centre in an external magnetic field to selectively address different electronic states and analyse the resulting fluorescence. We find evidence of selection rules in the optical transitions revealing that the centre possesses an electronic spin S = 1/2. Making use of the dependence of such selection rules on the applied magnetic field orientation, we resonantly drive two optical transitions forming a $\Lambda$-scheme. In the double resonance condition, we achieve coherent population trapping, whereby the SiV$^{−}$ is pumped into a dark state corresponding to a superposition of the two addressed ground states of opposite spin. This technique allows us to evaluate the coherence time of the dark state and hence of the spin, while demonstrating the possibility of all-optical control of the spin when a $\Lambda$-scheme is available. We then use resonant optical pulses to initialise and read out the spin state of a single SiV$^{−}$. By tuning a microwave pulse into resonance between two ground states of opposite spin, we demonstrate optically detected magnetic resonance. Subsequently, by varying the duration of a resonant microwave pulse, we achieve coherent control of a single SiV$^{−}$ electronic spin. Through Ramsey interferometry, we measure a spin dephasing time of 115 $\pm$ 9 ns. We then investigate interactions of the SiV$^{−}$ with its environment. We analyse the hyperfine interaction of the SiV$^{−}$ spin with the nuclear spin of $^{29}$Si, with a view to taking advantage of the long-lived nuclear spin in the future. We show that single-phonon-mediated excitations between electronic states of the SiV$^{−}$ are the dominant spin dephasing and population decay mechanism and evaluate how external strain alters optical selection rules and can be used to improve the coherence time of the spin.
2
Jahnke, Kay Daniel [Verfasser]. "Low temperature spectroscopy of single colour centres in diamond - The silicon-vacancy centre in diamond / Kay Daniel Jahnke." Ulm : Universität Ulm. Fakultät für Naturwissenschaften, 2015. http://d-nb.info/1074196023/34.
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Grazios, Fabio. "Fluorescence properties of single nitrogen-vacancy centre in diamond." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543481.
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Müller, Tina. "Novel colour centres in diamond : silicon-vacancy and chromium centres as candidates for quantum information applications." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608164.
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Hepp, Christian [Verfasser], and Christoph [Akademischer Betreuer] Becher. "Electronic structure of the silicon vacancy color center in diamond / Christian Hepp. Betreuer: Christoph Becher." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2014. http://d-nb.info/1064305822/34.
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Becker, Jonas Nils [Verfasser], and Christoph [Akademischer Betreuer] Becher. "Silicon vacancy colour centres in diamond : coherence properties & quantum control / Jonas Nils Becker ; Betreuer: Christoph Becher." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2017. http://d-nb.info/1152095226/34.
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Becker, Jonas Nils Verfasser], and Christoph [Akademischer Betreuer] [Becher. "Silicon vacancy colour centres in diamond : coherence properties & quantum control / Jonas Nils Becker ; Betreuer: Christoph Becher." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:291-scidok-ds-269890.
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Hubbard, Richard Ian. "Solid-state single-photon sources : quantum dots and the nitrogen-vacancy centre in diamond." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501140.
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Benedikter, Julia [Verfasser], and Theodor W. [Akademischer Betreuer] Hänsch. "Microcavity enhancement of silicon vacancy centres in diamond and europium ions in yttria / Julia Benedikter ; Betreuer: Theodor W. Hänsch." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2019. http://d-nb.info/1238518524/34.
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Abbasi, Zargaleh Soroush. "Spectroscopie d'excitation de la photoluminescence à basse température et resonance magnétique détectée optiquement de défauts paramagnétiques de spin S=l carbure de silicium ayant une photoluminescence dans le proche infrarouge." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLN044.
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Les défauts ponctuels dans les matériaux à grande bande interdite font l’objet de nombreuses recherches, compte tenu des perspectives d’applications en technologie quantique. La réalisation de qubits et de capteurs quantiques a échelle nanomètres à l’aide du centre NV– a suscité la recherche de défauts ayant des propriétés magnéto-optiques similaires, mais dans un matériau technologiquement plus mûr tel que le carbure de silicium (SiC). Le SiC se présente sous différentes structures cristallographiques, notamment cubique (3C) et hexagonales (4H et 6H). Cette propriété permet d’obtenir une plus grande variété de défauts ponctuels profonds. Dans cette thèse, j'ai établi présence du défaut azote-lacune (NCVSi) de spin S=1 dans un échantillon de 4H-SiC irradié par des protons, en réalisant la spectroscopie d'excitation de la photoluminescence à la température cryogénique et en comparant les résultats à des calculs ab initio. J'ai également développé un dispositif qui m'a permis de détecter optiquement la résonance magnétique de spin S=1 (ODMR) de la bilacune (VCVSi) dans un échantillon de 3C-SiC et d'étudier son interaction hyperfine avec des spins nucléaires d’atome de carbone et de silicium voisinsPoint-like defects in wide-bandgap materials are attracting intensive research attention owing to prospective applications in quantum technologies. Inspired by the achievements obtained with the NV– center in diamond for which qubit and nanoscale quantum sensors have been demonstrated, the search for high spin color centers with similar magneto-optical properties in a more technological mature material such as silicon carbide (SiC) had a renewed interest. Indeed, SiC exhibits polymorphism, existing for instance with cubic (3C polytype) or hexagonal (4H and 6H polytypes) crystalline structures. Such property provides a degree of freedom for engineering a rich assortment of intrinsic and extrinsic atomic-like deep defects. In this thesis using photoluminescence excitation spectroscopy at cryogenic temperature and a comparison to ab initio calculations I have evidence the presence of nitrogen-vacancy spin S=1 (NCVSi) defect in proton irradiated 4H-SiC. I have also developed a setup that allowed me to detect optically the S=1 spin magnetic resonance (ODMR) of the divacancy (VCVSi) in 3C-SiC, and study its hyperfine interaction with nearby carbon and silicon nuclear spins
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Oo, Thein Htay. "COUPLING NITROGEN VACANCY CENTERS IN DIAMOND TO A NANOMECHANICAL OSCILLATOR." Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23120.
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Exotic aspects of quantum mechanics, such as quantum entanglement, can be exploited to solve computational problems that are impractical to solve with conventional computers. With the realization of robust solid-state qubits, such as Nitrogen Vacancy (NV) centers in diamond, an outstanding challenge is to develop experimental approaches that can control the interactions between individual qubits. This dissertation develops a diamond-based experimental system that exploits acoustic waves or mechanical vibrations to mediate interactions between spin qubits. This spin-mechanical system features three essential elements: robust qubits, high quality-factor diamond nanomechanical resonator, and strong spin- mechanical coupling, thus enabling a new and promising platform for pursuing solid- state quantum computer.
For the spin-mechanical system, NV centers are created near the surface of a bulk diamond through nitrogen ion implantation followed by stepwise high temperature annealing. We successfully suppress environmental fluctuations and achieve NV centers with stable and spectrally narrow (< 50 MHz) fluorescence at low temperature, which is crucial for the spin-mechanical system.
Diamond nanomechanical resonators with a fundamental frequency near 1 GHz have been successfully fabricated with a diamond-on-insulator approach. The resonators are suspended from a silicon substrate and are supported with long and thin tethers, decoupling the mechanical modes from the surrounding environment. Diamond nanofabrication is still in its infancy. Numerous fabrication problems occurring during etching, mask transfer, and wafer bonding have been painstakingly resolved.
Strong spin-mechanical coupling is demonstrated via the strain coupling of the NV excited-states. The spin-mechanical coupling takes place through a 𝚲-type three- level system, where two ground-spin-states couple to an excited-state through a phonon-assisted as well as a direct dipole optical transition. Both coherent population trapping and optically-driven spin transitions have been realized. The coherent population trapping demonstrates the coupling between an acoustic wave and an electron spin coherence through a dark state, thus avoiding the short lifetime of the excited state. The optically-driven spin transitions can enable the quantum control of both spin and mechanical degrees of freedom.
This dissertation includes previously published co-authored material.
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Hong, Sungkun. "Nanoscale Magnetic Imaging with a Single Nitrogen-Vacancy Center in Diamond." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10671.
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Magnetic imaging has been playing central roles not only in fundamental sciences but also in engineering and industry. Their numerous applications can be found in various areas, ranging from chemical analysis and biomedical imaging to magnetic data storage technology. An outstanding problem is to develope new magnetic imaging techniques with improved spatial resolutions down to nanoscale, while maintaining their magnetic sensitivities. For instance, if detecting individual electron or nuclear spins with nanomter spatial resolution is possible, it would allow for direct imaging of chemical structures of complex molecules, which then could bring termendous impacts on biological sciences. While realization of such nanoscale magnetic imaging still remains challenging, nitrogen-vacancy (NV) defects in diamond have recently considered as promising magnetic field sensors, as their electron spins show exceptionally long coherence even at room temperature. This thesis presents experimental progress in realizing a nanoscale magnetic imaging apparatus with a single nitrogen-vacancy (NV) color center diamond. We first fabricated diamond nanopillar devices hosting single NV centers at their ends, and incorporated them to a custom-built atomic force microscope (AFM). Our devices showed unprecedented combination of magnetic field sensitivity and spatial resolution for scanning NV systems. We then used these devices to magnetically image a single isolated electronic spin with nanometer resolution, for the first time under ambient condition. We also extended our study to improve and generalize the application of the scanning NV magnetometer we developed. We first introduced magnetic field gradients from a strongly magnetized tip, and demonstrated that the spatial resolution can be further improved by spectrally distinguishing identical spins at different locations. In addition, we developed a method to synchronize the periodic motion of an AFM tip and pulsed microwave sequences controlling an NV spin. This scheme enabled employment of 'AC magnetic field sensing scheme' in imaging samples with static and spatially varying magnetizations.Engineering and Applied Sciences
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Alsid, Scott T. "Optimizing chemical-vapor-deposition diamond for nitrogen-vacancy center ensemble magnetometry." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112367.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2017.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 119-125).
The nitrogen-vacancy (NV) center in diamond has emerged as a promising platform for high-sensitivity, vector magnetic field detection and high spatial resolution magnetic-field imaging due to its unique combination of optical and spin properties. NV diamond magnetometry has enabled a wide array of applications from the noninvasive measurement of a single neuron action potential to the mapping [mu]T-fields in [mu]m-size meteorite grains. To further improve the magnetic sensitivity of an ensemble NV magnetometer, the growth and processing of the host diamond must be taken into account. This thesis presents a systematic study of the effects of diamond processing on bulk chemical-vapor-deposition diamond. In particular, NV charge-state composition and spin decoherence times are measured for diamonds irradiated with 1 MeV electrons at doses of 1x1015-5x1019 e-/cm2 and thermally annealed at temperatures of 850°C and 1250°C. The study provides an optimal range for diamond processing and shows the quenching of the NV center at high irradiation dosage from the creation of additional vacancy-related defects.
by Scott T. Alsid.
S.M.
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Wolf, Michael Scott. "COUPLING NITROGEN-VACANCY CENTER SPINS IN DIAMOND TO A FERROMAGNETIC VORTEX." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1491817964933604.
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Dinyari, Khodadad. "Coupling Nitrogen Vacancy Centers in Diamond Nanopillars Whispering Gallery Microresonators." Thesis, University of Oregon, 2013. http://hdl.handle.net/1794/12962.
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For cavity quantum electrodynamics systems (cavity-QED) to play a role in quantum information processing applications and in quantum networks, they must be robust and scalable in addition to having a suitable method for the generation, processing and storage of quantum bits. One solution is to develop a composite system that couples a nitrogen vacancy (NV) center in diamond to a whispering gallery mode supported by a fused silica microsphere. Such a system is motivated by the optical and electron-spin properties of the NV center. The NV center is the leading spin-qubit and exhibits atomic like linewidths at cryogenic temperatures and has spin coherence times greater than milliseconds at room temperature. These long coherence times, coupled with nanosecond scale spin readout and manipulation times, allow for millions of quantum operations to be processed. Silica whispering gallery resonators are the only class of microresonators with quality factor high enough to reach the strong coupling regime, which is necessary for some quantum information processing applications.
Integrating these two components into a system that could position a diamond nanopillar near the surface of a deformed-double stemmed microsphere system, with nanometer precision, at 10 K was a major achievement of this research. Cavity resonances in deformed microspheres can be excited with a free-space coupling technique which simplifies their integration into cryogenic environments. In these intentionally deformed resonators, an enhanced evanescent field decay length was observed at specific locations along the ray orbit. The double-stem arrangement enables the cavity resonance to be tuned over 450 GHz, with sub-10 MHz resolution, at 10 K. These two features, the enhanced decay length and broad range tuning with high resolution, are indispensible tools for cavity-QED studies with silica microspheres.
Diamond nanopillars were fabricated from single crystal diamond with diameters as small as 140 nm in order to maintain a high quality factor. Studies were conducted on NV centers in nanopillars and bulk diamond to determine their suitability for cavity-QED applications. In an attempt to increase the light-matter interaction between NV centers and whispering gallery modes, diamond substrates were optically characterized that were irradiated with nitrogen ions.
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Amezcua, Mayra. "Optical and Mechanical Quantum Control of Nitrogen Vacancy Centers in Diamond." Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23743.
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Current proposals for the design of quantum computer architectures include combining different quantum systems with designated tasks to build a device that can efficiently store, process, and transfer quantum information. Electron spins in solid-state quantum systems are a viable platform for storing information in these multi-quantum frameworks. While extensive research has been performed to couple solid-state systems to photons and microwaves, an alternative line of research focuses on coupling these systems to phonons, or mechanical motion. The use of phonons in solid-state devices opens up a new approach to interface different quantum systems.
This dissertation presents experimental progress in developing and controlling a spin-mechanical system, specifically the interaction between the electron spin of a nitrogen vacancy (NV) center in diamond and mechanical vibrations on the surface of the diamond, and discusses theoretical methods for limiting decoherence in the system. To investigate the strain properties of the NV center, we couple acoustic waves to the NV spin via an optical excitation. We transfer population between the spin ground states by driving phonon-assisted optical transitions and demonstrate the formation of a non-radiative state, which can be used to adiabatically transfer population between two states, through the same mechanism. To mitigate the effects of the nuclear spin bath on the NV center, we study and show preliminary results on the semiclassical dressed states, or quantum states of the NV interacting with optical fields. The dressed states can be insensitive to magnetic fluctuations, thus preserving the quantum state of the system. Finally, we consider a transitionless quantum driving technique that decouples the NV center from a radiative state, preventing decoherence through spontaneous emission. These developments are essential in advancing our understanding of phonon-based interfaces between quantum systems.
This dissertation includes previously published and unpublished co-authored material.
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Johnson, Sam. "The coupling of Nitrogen-Vacancy centres in diamond to tunable open-microcavities." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:a55eecba-645d-4755-8a17-d183fe8fa678.
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The Nitrogen-Vacancy (NV) centre in diamond possesses an optical read out of its spin state and shows great promise for applications in solid state quantum technologies. Its broad phonon assisted emission spectrum, with only 4% of emission from the zero-phonon line, is a major drawback to this. The optical microcavity will be essential in efficiently interfacing these centres with photonic networks. Here we present investigations into the coupling of NV centres in nanodiamond to tunable open-microcavities, both at room temperature and at cryogenic temperatures. These structures will be shown to achieve good photon confinement, with mode volumes down to 5λ3. Room temperature studies on ensembles of NVs will illustrate the tunable spectral and spatial overlap between the emitter and the cavity mode. It will be shown that small enhancements are possible in this regime. After the preparation and characterisation of single emitters, low temperature coupling to the narrowed zero-phonon line will be the central theme of this thesis. Single photon emission into the cavity mode is verified. We observe the enhancement of the light-matter interaction in this regime, by a 39% increase in the emission rate when cavity-coupled, with the dependence on mode volume also demonstrated. These results are important for the realisation of a spin-photon interface in scalable quantum networks.
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Purser, Carola Midori. "Magnetic Resonance Detection using Nitrogen-Vacancy Centers in Diamond." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1560279273608591.
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Pham, Linh My. "Magnetic Field Sensing with Nitrogen-Vacancy Color Centers in Diamond." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10993.
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In recent years, the nitrogen-vacancy (NV) center has emerged as a promising magnetic sensor capable of measuring magnetic fields with high sensitivity and spatial resolution under ambient conditions. This combination of characteristics allows NV magnetometers to probe magnetic structures and systems that were previously inaccessible with alternative magnetic sensing technologies. This dissertation presents and discusses a number of the initial efforts to demonstrate and improve NV magnetometry. In particular, a wide-field CCD based NV magnetic field imager capable of micron-scale spatial resolution is demonstrated; and magnetic field alignment, preferential NV orientation, and multipulse dynamical decoupling techniques are explored for enhancing magnetic sensitivity. The further application of dynamical decoupling control sequences as a spectral probe to extract information about the dynamics of the NV spin environment is also discussed; such information may be useful for determining optimal diamond sample parameters for different applications. Finally, several proposed and recently demonstrated applications which take advantage of NV magnetometers' sensitivity and spatial resolution at room temperature are presented, with particular focus on bio-magnetic field imaging.Engineering and Applied Sciences
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Terada, Daiki. "Ultra-small diamond quantum sensor for bioapplications." Kyoto University, 2020. http://hdl.handle.net/2433/253301.
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Babinec, Thomas Michael. "Topics in Nanophotonic Devices for Nitrogen-Vacancy Color Centers in Diamond." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10461.
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Recently, developments in novel and high-purity materials allow for the presence of a single, solitary crystalline defect to define the electronic, magnetic, and optical functionality of a device. The discrete nature of the active dopant, whose properties are defined by a quantum mechanical description of its structure, enables radically new quantum investigations and applications in these arenas. Finally,there has been significant development in large-scale device engineering due to mature semiconductor manufacturing techniques. The diverse set of photonic device architectures offering light confinement, guiding, and extraction is a prime example. These three paradigms – solitary dopant photonics and optoelectronics (solotronics), quantum science and technology, and device engineering – merge in the development of novel quantum photonic devices for the next generation of information processing systems. We present in this thesis a series of investigations of optical nanostructures for single optically active spins in single crystal diamond. Chapter 1 introduces the Nitrogen-Vacancy (NV) color center, summarizes its applications, and motivates the need for their integration into photonic structures. Chapter 2 describes two prototype nanobeam photonic crystal cavities for generating strong light-matter interactions with NV centers. The first device consists of a silicon nitride photonic crystal nanobeam cavity with high quality factor \(Q \sim 10^5\) and small mode volume \(V \sim 0.5*(\lambda/n)^3\). The second device consists of a monolithic diamond nanobeam cavity fabricated with the focused ion beam (FIB) directly in a single crystal diamond sample. Chapter 3 presents a high-efficiency source of single photons consisting of a single NV center in a photonic diamond nanowire. Early FIB prototypes are described, as is the first successful realization of the device achieved via reactive ion etching nanowires in a single crystal diamond containing NV centers, and finally a variation of this approach based on incorporation of NV centers in pure diamond via ion implantation. In chapter 4 we consider the optimal design of photonic devices offering both collection efficiency and cavity-enhancements and extend the model of the NV center to include photonic effects. In chapter 5 we briefly introduce a novel optically active spin discovered in a diamond nanowire. Finally, in chapter 6 we conclude with several proposals to extend this research program.Engineering and Applied Sciences
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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.
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Shields, Brendan John. "Diamond platforms for nanoscale photonics and metrology." Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11638.
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Observing and controlling solid state quantum systems is an area of intense research in quantum science today. Such systems offer the natural advantage of being bound into a solid device, eliminating the need for laser cooling and trapping of atoms in free space. These solid state "atoms" can interface directly with photonic channels designed to efficiently couple into larger networks of interacting quantum systems. With all of the tools of semiconductor fabrication technology available, the idea of scalable, chip-based quantum networks is a tantalizing prospect.Physics
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Schröder, Tim. "Integrated photonic systems for single photon generation and quantum applications." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://dx.doi.org/10.18452/16723.
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Im Rahmen der vorliegenden Dissertation wurden neuartige integrierte Einzelphotonenquellen (EPQ) und ihre Anwendung für die Quanteninformationsverarbeitung entwickelt und untersucht. Die Erzeugung von Einzelphotonen basiert auf einzelnen Defektzentren in nanometergroßen Diamantkristallen mit einzigartigen optischen Eigenschaften: Stabilität bei Zimmertemperatur ohne optisches Blinken. Diamantkristalle mit Größen bis unter 20nm wurden mit neuartigen „pick-and-place“ Techniken (z.B. mit einem Atomkraftmikroskop) in komplexe photonische Strukturen integriert. Zwei unterschiedliche Ansätze für die Realisierung der neuartigen EPQ wurden verfolgt. Beim ersten werden fluoreszierende Diamantkristalle in nano- und mikrometergroße Faser-basierte oder resonante Strukturen in einem „bottom-up“ Ansatz integriert, dadurch werden zusätzliche optische Komponenten überflüssig und das Gesamtsystem ultra-stabil und wartungsfrei. Der zweite Ansatz beruht auf einem Festkörperimmersionsmikroskop (FIM). Seine Festkörperimmersionslinse wirkt wie eine dielektrische Antenne für die Emission der Defektzentren. Es ermöglicht die höchsten bisher erreichten Photonenzählraten von Stickstoff-Fehlstellen von bis zu 2.4Mcts/s und Einsammeleffizienzen von bis zu 4.2%. Durch Anwendung des FIM bei cryogenen Temperaturen wurden neuartige Anwendungen und fundamentale Untersuchungen möglich, weil Photonenraten signifikant erhöht wurden. Die Bestimmung der spektralen Diffusionszeit eines einzelnen Defektzentrums (2.2µs) gab neue Erkenntnisse über die Ursachen von spektraler Diffusion. Spektrale Diffusion ist eine limitierende Eigenschaft für die Realisierung von Quanteninformationsanwendungen. Das Tisch-basierte FIM wurde außerdem als kompakte mobile EPQ mit Ausmaßen von nur 7x19x23cm^3 realisiert. Es wurde für ein Quantenkryptographie-Experiment implementiert, zum ersten Mal mit Siliziumdefektzentren. Des Weiteren wurde ein neues Konzept für die Erzeugung von infraroten EPQ entwickelt und realisiert.The presented thesis covers the development and investigation of novel integrated single photon (SP) sources and their application for quantum information schemes. SP generation was based on single defect centers in diamond nanocrystals. Such defect centers offer unique optical properties as they are room temperature stable, non-blinking, and do not photo-bleach over time. The fluorescent nanocrystals are mechanically stable, their size down to 20nm enabled the development of novel nano-manipulation pick-and-place techniques, e.g., with an atomic force microscope, for integration into photonic structures. Two different approaches were pursued to realize novel SP sources. First, fluorescent diamond nanocrystals were integrated into nano- and micrometer scaled fiber devices and resonators, making them ultra-stable and maintenance free. Secondly, a solid immersion microscope (SIM) was developed. Its solid immersion lens acts as a dielectric antenna for the emission of defect centers, enabling the highest photon rates of up to 2.4Mcts/s and collection efficiencies of up to 4.2% from nitrogen vacancy defect centers achieved to date. Implementation of the SIM at cryogenic temperatures enabled novel applications and fundamental investigations due to increased photon rates. The determination of the spectral diffusion time of a single nitrogen vacancy defect center (2.2µs) gave new insights about the mechanisms causing spectral diffusion. Spectral diffusion is a limiting property for quantum information applications. The table-top SIM was integrated into a compact mobile SP system with dimension of only 7x19x23cm^3 while still maintaining record-high stable SP rates. This makes it interesting for various SP applications. First, a quantum key distribution scheme based on the BB84 protocol was implemented, for the first time also with silicon vacancy defect centers. Secondly, a conceptually novel scheme for the generation of infrared SPs was introduced and realized.
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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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Goss, Jonathan Paul. "A first principles study of defects in semiconductors." Thesis, University of Exeter, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361336.
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Riedrich-Möller, Janine, Sébastien Pezzagna, Jan Berend Meijer, Christoph Pauly, Frank Mücklich, Matthew Markham, Andrew M. Edmonds, and Christoph Becher. "Nanoimplantation and Purcell enhancement of single nitrogen-vacancy centers in photonic crystal cavities in diamond." AIP Publishing, 2015. https://ul.qucosa.de/id/qucosa%3A31859.
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We present the controlled creation of single nitrogen-vacancy (NV) centers via ion implantation at
the center of a photonic crystal cavity which is fabricated in an ultrapure, single crystal diamond
membrane. High-resolution placement of NV centers is achieved using collimation of a
5 keV-nitrogen ion beam through a pierced tip of an atomic force microscope. We demonstrate
coupling of the implanted NV centers’ broad band fluorescence to a cavity mode and observe
Purcell enhancement of the spontaneous emission. The results are in good agreement with a master
equation model for the cavity coupling.
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Tisler, Julia [Verfasser]. "Nitrogen-vacancy center in diamond as sensor for Fluorescence Resonance Energy Transfer Scanning Near Field Optical Microscopy / Julia Tisler." München : Verlag Dr. Hut, 2014. http://d-nb.info/1050331583/34.
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Neumann, Philipp [Verfasser], and Jörg [Akademischer Betreuer] Wrachtrup. "Towards a room temperature solid state quantum processor - the nitrogen-vacancy center in diamond / Philipp Neumann. Betreuer: Jörg Wrachtrup." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2012. http://d-nb.info/102469254X/34.
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Amponsah, Sylvester. "Optical Characterization of Nitrogen-vacancy Centers andResonance Analysis of CVD Grown Diamond MEMS Devices." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1528479091207253.
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Albrecht, Roland Christoph [Verfasser], and Christoph [Akademischer Betreuer] Becher. "Coupling of a single nitrogen-vacancy center in diamond to a fiber-based microcavity / Roland Christoph Albrecht. Betreuer: Christoph Becher." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2014. http://d-nb.info/1054054800/34.
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Gonzalez, Gabriel. "ELECTRON TRANSPORT IN SINGLE MOLECULE MAGNET TRANSISTORS AND OPTICAL LAMBDA TRANSITIONS IN THE NITROGEN-VACANCY CENTER IN DIAMON." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2976.
Full textAbstract:
This thesis presents some theoretical studies dealing with quantum interference effects in electron transport through single molecule magnet transistors and a study on optical non-conserving spin transitions in the Nitrogen-vacancy center in diamond. The thesis starts with a brief general introduction to the physics of quantum transport through single electron transistors. Afterwards, the main body of the thesis is divided into three studies: (i) In chapter (2) we describe the properties of single molecule magnets and the Berry phase interference present in this nanomagnets. We then propose a way to detect quantum interference experimentally in the current of a single molecule magnet transistor using polarized leads. We apply our theoretical results to the newly synthesized nanomagnet Ni4. (ii) In chapter (3) we review the Kondo effect and present a microscopic derivation of the Kondo Hamiltonian suitable for full and half integer spin nanomagnets. We then calculate the conductance of the single molecule magnet transistor in the presence of the Kondo effect for Ni4 and show how the Berry phase interference becomes temperature dependent. (iii) We conclude in chapter (4) with a theoretical study of the single Nitrogen vacancy defect center in diamond. We show that it is possible to have spin non-conserving transitions via the hyperfine interaction and propose a way to write and read quantum information using circularly polarized light by means of optical Lambda transitions in this solid state system.Ph.D.
Department of Physics
Sciences
Physics PhD
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Neu, Elke Katja [Verfasser], and Christoph [Akademischer Betreuer] Becher. "Silicon vacancy color centers in chemical vapor deposition diamond : new insights into promising solid state single photon sources / Elke Katja Neu. Betreuer: Christoph Becher." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2012. http://d-nb.info/1052338593/34.
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Neu-Ruffing, Elke [Verfasser], and Christoph [Akademischer Betreuer] Becher. "Silicon vacancy color centers in chemical vapor deposition diamond : new insights into promising solid state single photon sources / Elke Katja Neu. Betreuer: Christoph Becher." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2012. http://d-nb.info/1052338593/34.
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Dong, Wenzheng. "Quantum Information Processing with Color Center Qubits: Theory of Initialization and Robust Control." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103438.
Full textAbstract:
Quantum information technologies include secure quantum communications and ultra precise quantum sensing that are significantly more efficient than their classical counterparts. To enable such technologies, we need a scalable quantum platform in which qubits are con trollable. Color centers provide controllable optically-active spin qubits within the coherence time limit. Moreover, the nearby nuclear spins have long coherence times suitable for quantum memories. In this thesis, I present a theoretical understanding of and control protocols for various color centers. Using group theory, I explore the wave functions and laser pumping-induced dynamics of VSi color centers in silicon carbide. I also provide dynamical decoupling-based high-fidelity control of nuclear spins around the color center. I also present a control technique that combines holonomic control and dynamically corrected control to tolerate simultaneous errors from various sources. The work described here includes a theoretical understanding and control techniques of color center spin qubits and nuclear spin quantum memories, as well as a new platform-independent control formalism towards robust qubit control.Doctor of Philosophy
Quantum information technologies promise to offer efficient computations of certain algorithms and secure communications beyond the reach of their classical counterparts. To achieve such technologies, we must find a suitable quantum platform to manipulate the quantum information units (qubits). Color centers host spin qubits that can enable such technologies. However, it is challenging due to our incomplete understanding of their physical properties and, more importantly, the controllability and scalability of such spin qubits. In this thesis, I present a theoretical understanding of and control protocols for various color centers. By using group theory that describes the symmetry of color centers, I give a phenomenological model of spin qubit dynamics under optical control of VSi color centers in silicon carbide. I also provide an improved technique for controlling nuclear spin qubits with higher precision. Moreover, I propose a new qubit control technique that combines two methods - holonomic control and dynamical corrected control - to provide further robust qubit control in the presence of multiple noise sources. The works in this thesis provide knowledge of color center spin qubits and concrete control methods towards quantum information technologies with color center spin qubits.
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Page, Michael Roy. "Interactions between spin transport and dynamics studied using spatially resolved imaging and magnetic resonance." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480592093876192.
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Scozzaro, Nicolas Joseph. "Ultrasensitive Measurements of Magnetism in Carbon-based Materials." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu148059474280115.
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Jung, Young Woo. "Optical studies and biological applications of spins in semiconductors." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306523724.
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Harrison, Joanne Patrice. "Photodynamics of the nitrogen-vacancy colour centre in diamond." Phd thesis, 2006. http://hdl.handle.net/1885/109456.
Full textAbstract:
The nitrogen-vacancy (N-V⁻) colour centre in diamond has potential applications
in quantum information processing and single photon generation. It
is currently the only known defect in a solid detected at a single site level
that has a non-zero spin in the electronic ground state. For the proposed
applications it is desirable to have a good understanding of the electronic
structure and photodynamics of the centre, however this is currently not the
case. Various models have been proposed to explain the fluorescence characteristics
observed in single site experiments. The challenge has been to
also account for the properties of the centre well-known from observations of
the fluorescence from large ensembles of N-V⁻ in diamond. Firstly, that a
non-Boltzmann population distribution between the. ground state spin levels
is induced by optical excitation. Secondly, that the fluorescence intensity
exhibits a strong dependence on the spin orientation. The models proposed
to date either cannot account for these properties, or do so only by invoking
optical processes that are arbitrary or, in some cases, not physical.
In this thesis an alternative model is presented. The derivation of the
model, from group theoretical considerations, does not form part of this
thesis. This thesis is concerned primarily with a series of independent measurements
to determine the transition rates which govern the photodynamics
of the centre. When these transition rates are known, there will be no free
parameters in the model and the N-V⁻ emission can be simulated for an
arbitrary optical field by solving the classical rate equations. To conclude
the first part of this thesis, a two-pulse optical excitation is considered and
the results of experiment are compared to the predictions of the model.
The latter part of t his thesis is concerned with optically detecting single
N-V⁻ centres. A confocal microscope system, to enable single site detection,
was developed as part of this work. The photon statistics from a single N-V⁻ centre
is compared to the statistics predicted by the model. The implications
for the modelling of individual N-V⁻ photon statistics are discussed.
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Berhane, Amanuel Michael. "Spectroscopy of single photon emitting defects in Gallium Nitride and Diamond." Thesis, 2018. http://hdl.handle.net/10453/125516.
Full textAbstract:
University of Technology Sydney. Faculty of Science.A single photon is among the few quantum mechanical systems that are finding applications in myriad fields. The applications include serving as building blocks for the ongoing endeavour to realise faster computers and secure communication technologies. As a result, a variety of platforms are being inspected to generate single photons on-demand. Point defects and complexes in wide bandgap semiconductors such as nitrogen-vacancy (NV) and silicon-vacancy (SiV) centres in diamond, carbon antisite in Silicon Carbide (SiC), etcetera, are shown to be reliable room temperature (RT), single photon emitters (SPEs). Despite reports of several defect based SPEs in diamond and other semiconductors, the exploration continues to find ideal sources for applications. The central part of this work also focuses on the discovery and characterisation of novel SPE in the device fabrication friendly material- Gallium Nitride (GaN). The other important aspect in the study of SPEs is the method by which emitters are excited. While optical technique via laser excitation is the standard approach, electrically excited single photon generation is highly desirable for large-scale nanophotonic applications. The second part of the work investigates electrically driven fluorescence from SiV ensemble in diamond, whose properties so far, were only investigated using optical excitations. Therefore, the thesis consists of two main parts. First, the discovery as well as study of a new family of SPEs in GaN via optical excitation is covered. The second part features electrically driven characterisation of SiV centre in diamond. The RT stable, SPEs are discovered in GaN films using a confocal microscope. The emitters are off-resonantly excited using a continuous wave (cw) laser of wavelength 532 nm. The centre of wavelength in the emission spectra spans a wide range of from around 600 nm to 780 nm. Also, a significant portion of the emission comes from the characteristic, narrow zero-phonon lines (ZPLs) with the mean cryogenic and RT Full Width at Half Maximum (FWHM) of around 0.3 nm and 5 nm, respectively. The nature of the defect responsible for the emission is studied experimentally via temperature resolved spectroscopy as well as numerical modelling giving a strong indication that the emitter is a defect localised near cubic inclusions. Absorption and emission polarisation properties from the SPEs in GaN is studied in detail via polarization-resolved spectroscopy. High degree of linear, emission polarisation is observed with an average visibility of more than 90 %. The absorption polarisation measurement shows that individual emitters may have different dipole orientation. In addition, brightness measurements from several of the SPEs in GaN show the average maximum intensity of around 427 kCounts/s placing the emitters among the brightest reported so far. A three-level model describes the transition kinetics of the SPEs successfully which explains some of the observed properties of the emitters such as photon statistics. A small number of the SPEs in GaN show unusual photo-induced blinking. This blinking is shown to be due to a permanent change in the transition kinetics of the emitters when exposed to a laser power above a certain threshold. This is evidenced by the change in the transition kinetics observed before and after blinking of SPEs. Combining long-time autocorrelation measurement and photon statistics analysis, numerical values for power-dependent blinking behaviours are determined. The second major result in this work is the first electrically driven luminescence from the negative charge state of Silicon-Vacancy (SiV⁻). The result was directly obtained by measuring photoluminescence (PL) and electroluminescence (EL) spectra from SiV⁻ ensemble located in PIN diamond diode. The defect was incorporated into the diode via ion implantation. Further characterisation shows that the saturation behaviour under excess carrier injection yields similar results with when the defect is pumped optically by lasers. Finally, charge state switching between the negative and neutral states of the defect was also attempted by using reverse-biased PL elucidating transition dynamics of SiV centres in diamond. This work, therefore, reports new findings in the spectroscopic studies of defect based single photon emission. Furthermore, it provides detailed photophysical studies which may serve as a benchmark for future investigation of SPEs in GaN for multiple applications. The results provide new platform as well as alternative excitation approach for the application of defect based SPEs in nanophotonics.
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Rogers, Lachlan James. "Optical pumping cycle of the negative nitrogen-vacancy centre in diamond." Phd thesis, 2012. http://hdl.handle.net/1885/155811.
Full textAbstract:
The negative Nitrogen-Vacancy (NV) colour centre in diamond is an atomic-level impurity that is remarkably well suited for quantum information processing and quantum metrology applications. Underlying these properties is the fact that optical illumination causes the NV centre to preferentially populate one of its three spin levels. The mechanism that gives rise to this spin polarisation has not been well understood, despite intense research interest in the NV centre and its applications. This thesis arrives at an account of the spin polarisation mechanism, although a detailed theoretical treatment remains outstanding. The energy level structure of the NV centre is investigated using techniques of solid state spectroscopy. These include absorption and photoluminescence measurements made on diamonds at cryogenic and room temperatures in the presence of uniaxial stress, magnetic fields, and microwaves. Pulsed light experiments allow the dynamic processes within the NV centre to be measured. It is shown that at room temperature the orbital doublet excited state behaves like an orbital singlet, and this description is elegantly confirmed by single-site observations. This picture of the excited state is inconsistent with cryogenic measurements, and its behaviour is examined across a range of temperatures in order to resolve this tension. It is shown that electron-vibration interaction accounts for the quenching of orbital properties in the excited state with temperature. A new optical transition within the NV centre is reported at a wavelength of 1042 nm. It is established that this transition occurs between the intermediate singlet levels which are thought to provide the decay pathway that produces spin polarisation. The results are consistent with this understanding, and the order and properties of these singlet levels are established. Electron-vibration interaction is observed to be important within the singlet system. It is shown that electron-vibration interaction is an important detail in the NV optical pumping cycle. Taking it into consideration leads to the first plausible physical description of the spin polarisation mechanism. -- provided by Candidate.
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He, Xing-Fei. "Raman heterodyne detected magnetic resonance of the nitrogen-vacancy centre in diamond." Phd thesis, 1991. http://hdl.handle.net/1885/109549.
Full textAbstract:
This thesis describes the Raman heterodyne detection of magnetic resonance in the ³A
ground state of the nitrogen-vacancy C'-1· V) centre in diamond. The recently developed theory of
Raman heterodyne spectroscopy was tested and compared with the spectra measured on the N-V
centre. Among those results, the electron-nuclear double resonance (ENDOR), nuclear-nuclear
double resonance (double NMR), Autler-Townes effect, coherence transfer and Zeeman quantum
beat were observed for the first time using such techniques. Raman heterodyne techniques were
also used to investigate the level anticrossing, hyperfine and nuclear quadrupole interactions, and
spin relaxations of the N-V centre with high sensitivity and precision.
This thesis is comprised of three parts. Part one includes Chapters 1 to 3, providing
introductory accounts. Chapter l is an introduction to the N-V colour centre, which describes
the defect configuration, the spin Hamiltonian and the calculations of energy levels and wave
functions of the ³A ground state. Chapter 2 briefly describes the theory of Raman heterodyne
spectroscopy - a coherent optical radio-frequency (RF) double resonance technique, in particular
the Raman heterodyne signals at weak and intense RF fields. Chapter 3 deals with experimental
details and techniques utilized in the studies.
Part two consists of Chapters 4 and 5, where the Raman heterodyne theory is compared
with experimental results. Chapter 4 presents the Raman heterodyne detected nuclear magnetic
resonance (NMR) and electron paramagnetic resonance (EPR) lineshapes compared with
theoretical results at various RF power levels, laser intensities and laser frequencies within the
6380A zero-phonon line. The double resonance spectra obtained by Raman heterodyne
techniques are discussed in Chapter 5, where attention is paid to the analysis of their spectral profiles depending on the detection scheme.
The application of Raman heterodyne techniques to the studies of magnetic resonance of the
N-V centre is described in part three, consisting of Chapters 6 to 9. The EPR measurements are
described in Chapter 6, which were used to study various interactions near the level anticrossing,
in particular the spin alignment. The hyperfine and nuclear quadrupole interactions probed by the
NMR, ENDOR and hole burning measurements are described in Chapter 7. From these
measurements, the hyperfine and quadrupole parameters in the spin Hamiltonian were fully
determined. Chapter 8 deals with the Autler-Townes effect in the NMR and EPR transitions. By
measuring the Autler-Townes spittings, the magnitudes of matrix elements of the NMR
transitions were examined and compared. Chapter 9 presents the coherent spin transient
properties, including nutations, echoes, Zeeman beating and coherence transfer. The dephasing
time and homogeneous linewidths of the NMR and EPR transitions were then determined from
the echo measurements.
Finally, the thesis is summarized in Chapter 10.
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Barson, Michael Samuel James. "The mechanical and thermal properties of the nitrogen-vacancy centre in diamond." Phd thesis, 2018. http://hdl.handle.net/1885/154250.
Full textAbstract:
Quantum technologies offer revolutionary new ways to perform
metrology and process information. However, successfully
exploiting quantum devices for new practical technology is a
challenging problem. Due to the fragile nature of quantum states,
precision measurements and operations using quantum objects are
often confined to systems that are well protected from their
environment. This can limit the practical use of such quantum
devices. A quantum tool that can successfully and simply operate
in ambient conditions would provide major advances in quantum
technology.
In the past decade or so, the nitrogen-vacancy (NV) centre in
diamond has proven itself to be a remarkably powerful tool for
nanoscale quantum sensing and quantum information processing in
ambient conditions. Despite these achievements, there are still
several fundamental features of the NV centre which are not
completely understood. This thesis addresses these areas in two
parts, firstly the mechanical properties and secondly the thermal
properties of the NV centre.
The effect of crystal stress or strain on the spin resonances on
the NV centre ground state is theoretically described and then
experimentally characterised; correcting previously contradictory
attempts to explain the observed behaviour. The utility of this
knowledge is demonstrated by force sensing in a microscopic
diamond cantilever using a single NV centre. New unique concepts
of force sensing and metrology based on the NV spin-mechanical
interaction are explored.
The thermal properties of the NV centre’s optical and spin
resonances are theoretically described and experimentally
characterised; providing the first successful description that
details the origin of the effect of temperature on the spin
resonance. Furthermore, the atomscopic changes in the NV centre's
electronic orbitals due to the effect of crystal distortion are
directly probed.
This complete understanding of the NV centre's mechanical and
thermal behaviour enables metrology that spans the full
magnetic-temperature-pressure range of the NV centre. For
example, this is ideally suited to studying superconducting phase
changes in high-pressure materials. A proof of principle
measurement of phase changes in superconductors is demonstrated
and new magnetic-temperature-pressure metrology devices are
discussed.
Magnetic circular dichroism (MCD) spectroscopy measurements are
used to unpick some of the remaining mysteries of the NV centre.
The magnetic structure of the singlet levels are directly
measured for the first time and a large quenching of orbital
angular momentum is observed. This provides further evidence of a
Jahn-Teller interaction and its role in the lower inter-system
crossing. These MCD observations greatly enhance the knowledge
of the poorly understood, but critically important lower
inter-system crossing.
Using MCD the fine-structure of the NV0, ground and excited
states are measured for the first time and the reasons of their
absence from previous measurements are discussed. The observation
of the fine structure of NV0, ground state has been a
long-standing mystery of the NV centre, this information will
enable the pursuit of new applications of the NV centre that also
incorporate NV0.
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Patange, Om. "On an Instrument for the Coherent Investigation of Nitrogen-Vacancy Centres in Diamond." Thesis, 2013. http://hdl.handle.net/10012/7955.
Full textAbstract:
It is my hope that this thesis may serve as a guide for future students wishing to build a microscope from scratch. The design and construction of a scanning, confocal fluorescence microscope equipped with shaped microwave excitation is detailed. The use of the microscope is demonstrated by coherently manipulating single Nitrogen-Vacancy centres in diamond. Further the instrument is used to investigate a dual Halbach array magnet system.
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Semonyo, Malehlohonolo. "An experimental study of diamond and the nitrogen vacancy centre as a source of single photons." Thesis, 2009. http://hdl.handle.net/10413/8320.
Full textAbstract:
For applications in Quantum Information and Quantum Key Distribution an on-demand source of single photons is desirable because absolute security is of utmost importance. Photons are quantum systems; hence encoding information onto them offers a secure alternative to classical cryptography as a measurement cannot be performed on photons without altering their properties. The Nitrogen Vacancy (NV) centre in diamond is a good source of such photons. It is photo-stable and its location in diamond offers robustness. It has zero phonon line at 637 nm and its relative short luminescence life-time of about 12 ns makes it suitable for generating single photons. This thesis covers two aspects: Firstly the characterization of defects in diamonds and subsequent selection of diamonds suitable for use in the single photon setup and secondly, the development of the experimental setup for single photon generation. This thesis sets out to describe the development of a laboratory based single photon source using the NV centre in diamond. For this purpose a suite of diamond samples were selected and subjected to various spectroscopic tests in order to characterize and classify the samples, especially the presence of the NV centres and their concentrations. The characterization of the defects was done through the use of the following spectroscopic techniques: Ultraviolet-Visible-Near infrared spectroscopy, Infrared spectroscopy, Electron Spin Resonance and Photoluminescence. These techniques enabled us to understand the types and origins of crystal defects that were present in the diamond samples used in this study and to use this to select diamonds that are most suitable for use in generation of single photons. The experimental setup for single photon generation using the NV centre is based on a confocal microscope arrangement. Single NV centres were identified by measuring the second order autocorrelation function of the fluorescence light emitted by the sample when illuminated with a laser. This measurement was done using a Hanbury-Brown Twiss (HBT) interferometer.Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2009.
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Lai, Yen-Yu, and 賴彥佑. "Hybrid quantum memory with a single nitrogen-vacancy center in Diamond." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/vur42f.
Full textAbstract:
博士國立臺灣大學
物理學研究所
106
There are many kinds of physical quantum systems that have been proposed and realized as qubits to implement quantum computation and information processing. One may wish to have both the strong coupling strength between the qubit and an external control field and long coherence times for qubits: the former leads to fast and easy qubit operations; the latter maintains the coherence of the quantum state of the qubit. However, it is hard to have a qubit with both advantages. The systems, which can couple to other system strongly , are normally also easily influenced by the environment resulting in decoherence, and those with good coherence property due to the isolation from their environment cannot interact with other system well. So the idea of hybrid quantum system taking advantages of their constituents’ strengths has been proposed. Using the qubit with excellent coupling ability in the operating stage, and assisted by a quantum memory, which can transfer the quantum state between the operating qubit and storage qubit, one can avoid the decoherece in the idle time of the whole quantum processes. Here we propose a quantum memory scheme to transfer and store the quantum state of a superconducting flux qubit (FQ), as an operating unit, into the electron spin of a single nitrogen-vacancy (NV) center in diamond, as a storage unit, via a ferromagnet transducer, yttrium iron garnet (YIG). Unlike an ensemble of NV centers, the YIG moderator can enhance the effective FQ-NV-center coupling strength without introducing additional appreciable decoherence. We derive the effective interaction between the FQ and the NV center by tracing out the degrees of freedom of the collective mode of the YIG spins. We demonstrate the transfer, storage, and retrieval procedures, taking into account the effects of spontaneous decay and pure dephasing by a master equation in Lindblad form. Using realistic experimental parameters for the FQ, NV center and YIG, we find that a combined transfer, storage, and retrieval fidelity higher than 0.9, with a long storage time of 10 ms, can be achieved. This hybrid system not only acts as a promising quantum memory, but also provides an example of enhanced coupling between various systems through collective degrees of freedom.
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"Understanding and withstanding the decoherence of nitrogen-vacancy center spins in diamond." 2010. http://library.cuhk.edu.hk/record=b5894461.
Full textAbstract:
Ho, Sai Wah = 鑽石氮-空缺中心自旋的退相干研究及控制 / 何世華.Thesis (M.Phil.)--Chinese University of Hong Kong, 2010.
Includes bibliographical references (leaves 62-68).
Abstracts in English and Chinese.
Ho, Sai Wah = Zuan shi dan-kong que zhong xin zi xuan de tui xiang gan yan jiu ji kong zhi / He Shihua.
Chapter 1 --- Introduction --- p.1
Chapter 2 --- NV center in diamond --- p.6
Chapter 2.1 --- Why NV centers? --- p.6
Chapter 2.2 --- NV center --- p.8
Chapter 2.3 --- Hamiltonian of the spin system --- p.11
Chapter 3 --- Decoherence calculation - Cluster-correlation expansion --- p.13
Chapter 3.1 --- The decoherence problem --- p.13
Chapter 3.2 --- Quantum many-body theory: History and method --- p.17
Chapter 3.3 --- General theory of cluster-correlation expansion --- p.19
Chapter 3.4 --- Different physical processes and the pictorial understanding: Spin pathways in Bloch sphere --- p.21
Chapter 3.4.1 --- Dynamical fluctuation versus inhomogeneous broadening --- p.21
Chapter 3.4.2 --- Single nuclear spin dynamics --- p.22
Chapter 3.4.3 --- Nuclear spin pair dynamics --- p.24
Chapter 3.4.4 --- Higher order spin cluster dynamics --- p.27
Chapter 4 --- Dynamical decoupling theories and experiments --- p.28
Chapter 4.1 --- Dynamical decoupling: History --- p.28
Chapter 4.2 --- Pulse sequences --- p.29
Chapter 4.2.1 --- Spin echo (SE) --- p.30
Chapter 4.2.2 --- Carr-Purcell-Meiboom-Gill (CPMG) sequence --- p.31
Chapter 4.2.3 --- Concatenated dynamical decoupling (CDD) --- p.31
Chapter 4.2.4 --- Uhrig dynamical decoupling (UDD) --- p.32
Chapter 5 --- Dynamics of the spin clusters --- p.34
Chapter 5.1 --- Convergence of CCE under external magnetic field and pulse sequence --- p.34
Chapter 5.2 --- Zero magnetic field regime: single spin and spin pair induced dynamics --- p.35
Chapter 5.2.1 --- Free induction decay --- p.36
Chapter 5.2.2 --- Dynamical decoupling control: UDD1-5 --- p.37
Chapter 5.3 --- Small magnetic field regime: Single spin and spin pair induced dynamics --- p.38
Chapter 5.3.1 --- Single spin induced dynamics: single spin induced re- vivals under dynamical decoupling sequences --- p.38
Chapter 5.3.2 --- Single spin induced dynamics: Periodicity of revivals un- der different dynamical decoupling sequences --- p.42
Chapter 5.3.3 --- Single spin induced dynamics: Short time modulation and envelope under the effect of Fermi contact and dy- namical decoupling sequences --- p.45
Chapter 5.3.4 --- "Single spin and spin pair induced dynamics: Revival, os- cillation and decay under dynamical decoupling sequences" --- p.48
Chapter 5.4 --- Large magnetic field regime: Single spin and spin pair induced dynamics --- p.50
Chapter 5.4.1 --- Free induction decay --- p.50
Chapter 5.4.2 --- Dynamical decoupling control: UDD 1-5 --- p.52
Chapter 6 --- Application: Atomic scale magnetometry --- p.55
Chapter 7 --- Conclusion --- p.59
Bibliography --- p.62
Chapter A --- Derivation of modulation and envelope frequency using second order perturbation theory --- p.69
48
Mc, Murtrie Roger L. "Multi-wave mixing at radio frequencies by nitrogen vacancy centres in diamond." Master's thesis, 2006. http://hdl.handle.net/1885/150990.
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Tamang, Rajesh. "Fluorescence spectroscopy of nitrogen vacancy centers in HPHT and CVD diamonds." Doctoral thesis, 2016. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2016052614492.
Full textAbstract:
Diamond is a wide band gap material with many optically active defect centers. Among all, the most interesting negatively charged nitrogen vacancy (NV-) defect center in diamond has been investigated for almost two decades, often in relation to applications in quantum computing and quantum sensing.
Nitrogen vacancy centers are formed by a substitutional nitrogen atom next to a vacancy trapped at an adjacent lattice position. Usually, these centers are prepared in synthetic diamond, where single substitutional nitrogen impurities are in the ideal case homogenously dispersed. To obtain bright luminescence from a sample, additional vacancies are created by electron or neutron irradiation and allowing them to diffuse to nitrogen atoms by annealing at temperature above 600 0C. However, already untreated synthetic diamond samples provide a concentration of NV centers well suited for the study of ensembles. Therefore, to investigate ensemble luminescence centers in diamond crystals, the untreated samples are sufficient. The spectral analysis allowed to clearly identify NVs by fluorescence spectroscopy in such samples. Even at room temperature, the zero-phonon line (ZPL) at 638 nm (NV-) is clearly visible and an additional photon contribution results in the characteristic shape with an overall width of about 120 nm and a maximum at ~685 nm. The broad spectral emission is one of the few drawbacks of NV fluorescence.
In this thesis, I developed a conventional fluorescence detection technique, with a homebuilt sample stage which can be precisely positioned in x- and y- direction on a sub-micrometer scale. The sample is excited by laser light focused into a spot size of < 500 µm, and the fluorescence sampling is acquired within a sampling distance of 0.25 µm. Taking advantage of this, it is possible to take fluorescence sampling of an ensemble of NVs from the whole of the crystal, or from a desired section applying a fluorescence matrix methodology. Using this technique, a wide variety of CVD and HPHT synthesized diamond samples were investigated giving first-hand experience of omnipresent NV centers in diamond samples containing a nitrogen impurity concentration of less than 1 ppm (or <200 ppm). This study provides a good base for further work aiming at artificially creating near-surface NVs, which is the basis of many applications with the requirement for better sensitivity and strong coupling to the external spins.
To ensure that the fluorescence detected is reliable and repeatable, extensive fluorescence measurements were performed within different matrix regions of the sample for several days, and it turned out that the fluorescence emission is identical when the excitation laser is excited at the middle of the sample. The outcome of the experiments evolved in setting a reference sample for other fluorescence measurements. This reference sample was fluorescence measured over several months, and performed identical spectrum characteristic with less than 3-5% difference in absolute fluorescence intensity. In the spectrum, the often mixed Raman line at 573 nm and the NV0 centers were resolved using higher spectrometer grating.
A series of annealing studies in HPHT diamond samples was performed at UHV ambience with a base pressure at ~1 x 10-11 mbar on a sample with [N] < 200 ppm. The fluorescence examined on the sample annealed at temperature 500 0C revealed an increased fluorescence intensity, and remained at constant intensity on consecutive annealing cycles at the same temperature under the same conditions. However, at an increased temperature, the fluorescence emission increased, increasing NVs concentration in the crystal.
The untreated HPHT diamond crystals varied in fluorescence characteristic feature, but the sample showed the presence of NVs. The differences in spectroscopic features were identified as due to nitrogen content and possibilities of different nitrogen defect complexes present in the crystal, and they were modified when the sample was annealed at temperatures above 500 0C. The most effective defect formation within the crystal takes place at two temperature ranges 650 –750 0C and 800– 850 0C. The calculated activaction energy at 0.22 eV and 1.26 eV are the energy of mobile interstitial atoms and that of substitutional nitrogen atoms respectively. In the process of annealing, the desorbtion of nitrogen atoms from the surface crystal has been identified by a mass spectrometer. The study contributes to the fundemental understanding of anneling effects in diamond crystals, without being bombarded by high energy electron or neutron radiation. For the creation of a high density of NV centers, annealing in UHV could be sufficient, or even controlled NVs in ultra-pure diamond.
The CVD diamond crystals with [N] < 1ppm were observed to contain a high density of NVs, and had no significant change when the additional creations of NVs were attempted. Prolonged X-ray radiation followed by annealing of ultra-pure diamond ([N] <5ppb) during the XPS measurements, showed a significant impact in fluorescence intensity at the surface region confirmed by confocal measurements. However, the sensitivity of the fluorescence spectroscopy setup was not enough to observe the ZPL of the NV centers, though significant changes have been observed in the spectra. Finally, the shallow NV- creation with nitrogen ion implantation at energy of 1 keV has been confirmed by an ODMR experiment and confocal imaging.
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Kunuku, Srinivasu, and 蘇尼. "Study on synthesis and characterization of silicon-vacancy centers in diamond via chemical vapor deposition process." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/v63upg.
Full textAbstract:
博士國立清華大學
工程與系統科學系
105
Silicon-vacancy (SiV) centers in diamonds present exceptional spectral properties, including bright zero phonon line (ZPL) at wavelengths of 736 nm 746 nm and a narrow emission linewidth. As a single photon source, SiV center is a promising candidate for quantum computing as well as biomarking applications. The SiV centers in nanodiamonds, including diamond nanowires, diamond nanoislands, and diamond particles, present high-intensity of ZPL emissions over a narrow linewidth. In this study, we investigated the fabrication of ultrananocrystalline diamond (UNCD) nanostructures (UNCD size ~ 10 nm) and the spectral characteristics of the SiV centers contained within. SiV centers are typically created via chemical vapor deposition (CVD). In this process, Si impurities are incorporated within the diamond during the growth process, at elevated temperatures under high microwave powers. In this study, we created SiV centers in UNCD using two methods: (i) in-situ Si-doping during microwave plasma-enhanced chemical vapor deposition (MPECVD) at low growth temperatures; (ii) Si-ion implantation in UNCD and single crystalline diamond (SCD). The first method begins with in-situ Si-doping of diamond films with various granular structures grown on a Si-substrate at low temperature (< 550 oC). The films include microcrystalline diamond (MCD), nanocrystalline diamond (NCD), UNCD, and nitrogen-incorporated UNCD (N-UNCD) films. We devised a simple process for the fabrication of diamond nanostructures within these films using a self-assembled mask of Au nanodots followed by reactive ion etching (RIE) under O2/CF4 plasma. Field emission scanning electron microscopic images of the diamond nanostructures revealed the formation of vertical nanostructures with high density. UV-Raman spectroscopy confirmed that RIE did not degrade the quality of the diamond nanostructures. Photoluminescence (PL) spectroscopy revealed strong NV emissions from MCD nanocones and NCD nanotips as well as the quenching of NV emissions from UNCD nanopillars. The second process involves the in-situ Si-doping of diamond using various silicon oxide (SiO2) substrates, including SiO2, soda-lime glass, and soda-lime glass fibers, for the growth of MCD, NCD, and UNCD films. The PL spectra of the resulting UNCD diamond films revealed SiV centers with bright and clear emission at 738 nm - 740 nm and suppressed NV emissions. The UNCD formed as particulates rather than as a film on soda-lime glass fibers. Transmission electron microscopy (TEM) was used to study the influence of microstructure on the spectral characteristics of SiV centers. The TEM micrographs of UNCD films reveal the presence of large aggregate, which might be the cause of the NV emission from the UNCD films. We developed a simple process for the synthesis of SiV-UNCD particulates with bright emissions, wherein SiV-UNCD nanoclusters/soda-lime glass fibers were ultrasonicated in DI water, and then the water was spread over Si inverted pyramids. Time-resolved PL spectroscopy measurements of SiV-UNCD particulates revealed that the SiV centers have a short decay time of ~ 0.20 ns (SiV decay time ~ 1-2 ns). This can be attributed to the low quality of the UNCD, which includes a large number of defects and non-diamond carbon phases. We also developed two approaches to the fabrication of bright SiV-UNCD nanostructures; i.e., top-down approach for fabrication of SiV-UNCD nano-rods and bottom-up approach for fabrication of SiV-UNCD nano-tips. The resulting SiV-UNCD nanostructures exhibit bright emission over a narrow linewidth of ~ 7 nm 10.5 nm with shorter decay time of ~ 0.2 ns. To enhance the decay time of SiV centers, UNCD has grown on a Ti/Sapphire substrate using MPECVD, followed by Si-ion implantation under the following parameters: E = 125 keV and dose = 1013 ions/cm2. The resulting SiV-UNCD nanoclusters present bright SiV emission with ZPL width of ~ 7.0 nm and = 0.43 ns. Si-ion implantation was also performed on SCD (type Ia & type IIa) with E = 350 keV and dose = 1010 ions/cm2 to facilitate a comparison of the spectral characteristics of SiV-UNCD in high-quality diamond with SiV centers. The SiV centers in type IIa SCD present bright emission, narrow ZPL width of ~ 6 nm and enhanced decay time of = 1.30 ns. The SiV-UNCD nanostructures and SiV-UNCD particulates developed in this study have considerable potential in biomarking applications, due to their strong SiV emissions. Furthermore, the Si-ion implanted type IIa SCD samples are applicable as a single photon emitter in quantum information processing and quantum computation applications.