Dissertations / Theses: 'State of the photon'

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Reinhard, Andreas [Verfasser]. "Strong Photon-Photon Interactions in Solid State Cavity QED / Andreas Reinhard." München : Verlag Dr. Hut, 2013. http://d-nb.info/1034003194/34.

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Kiyohara, Takayuki. "Generation of heralded multi-photon parallel state for realizing a large-scale photonic quantum circuit." Kyoto University, 2020. http://hdl.handle.net/2433/253284.

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Beduini, Federica A. "Entanglement and state characterisation from two-photon interference." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/336093.

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This thesis analyses the effects of two-photon interference in a polarisation squeezed state under two different points of view: on one hand, it presents a new method to obtain the temporal wavefunction of a state of two photons; on the other hand, it studies the microscopic entanglement properties of a collective nonclassical polarisation state, such as the polarisation squeezed state. The complete characterisation of an unknown quantum state often requires complicated reconstruction methods due to its complex nature: in the first part of this thesis, we describe a new technique to recover completely the wavefunction of a state with two photons (a ¿biphoton¿) with just few simple measurements, thanks to the interference with a coherent reference. With this technique, we reconstruct successfully the wavefunction of single-mode biphotons from a low-intensity narrowband squeezed vacuum state. Many large collective systems that feature nonclassical properties, e.g. superconductivity and squeezing, show entanglement among their components at their microscopic level. Here we report the first direct study of this kind of entanglement for light polarisation. In analogy with the spin-squeezing inequalities that connect squeezing to entanglement for atomic ensembles, we derive an inequality valid for states with classical polarisation correlations, whose violation implies pairwise entanglement among the photons in the state. We consider a polarisation squeezed state that results from the combination in the same spatial mode of a squeezed vacuum state, generated by an optical parametric oscillator (OPO), and a coherent state with orthogonal polarisations: we find that this kind of state always violates our inequality within the coherence time of the squeezed vacuum state. We also quantify the entanglement between the photon pairs by computing the concurrence of the two-photon reduced density matrix: we find that the states that exhibit higher entanglement satisfy the condition for higher visibility of the two-photon interference. We also find that the concurrence is larger for lower squeezing levels, in agreement with the monogamy of entanglement and in analogy to the atomic case. This translation of spin-squeezing inequalities to the optical domain enables us to test directly the squeezing-entanglement relationship. We generate a squeezed vacuum state with an OPO and we combine it with a coherent state to generate a polarisation squeezed state and we measure the photon pair counts for different polarisation bases. We recover the density matrices corresponding to different realisations of the polarisation squeezed state via quantum tomography: all the density matrices that we reconstruct with this method are entangled, with concurrence up to 0.7. Our measurements confirm several theoretical predictions, including entanglement of all photon pairs within the squeezing coherence time.
En esta tesis se analizan los efectos de la interferencia de dos fotones en un estado comprimido en polarización desde dos puntos de vista: por un lado, se presenta un nuevo método para obtener la función de onda temporal de un estado de dos fotones; por el otro, se estudian las propiedades de entrelazamiento microscópico de un estado colectivo de polarización no clásico, como el estado comprimido en polarización. La completa caracterización de un estado cuántico desconocido requiere frecuentemente métodos de reconstrucción complicados debido a su compleja naturaleza: en la primera parte de esta tesis describimos una nueva técnica para recuperar completamente la función de onda de un estado con dos fotones (un bifotón) usando pocas medidas sencillas, gracias a la interferencia con un estado coherente de referencia. Con esta técnica, reconstruimos con éxito la función de onda de los bifotones que pertenecen a un estado de vacío comprimido de banda estrecha y de baja intensidad. Muchos sistemas colectivos con un gran número de partículas que presentan propiedades no clásicas, como por ejemplo superconductividad y estados comprimidos, muestran entrelazamiento entre sus componentes a nivel microscópico. Aquí describimos el primer estudio directo de este tipo de entrelazamiento para los estados de polarización de la luz. En analogía con las desigualdades para estados comprimidos en espín, derivamos una desigualdad válida para estados con correlaciones clásicas en polarización, cuya violación implica entrelazamiento en parejas entre los fotones del estado. Consideramos un estado comprimido en polarización, que es el resultado de la combinación en el mismo modo espacial de un estado de vacío comprimido generado por un oscilador óptico paramétrico (OPO) y de un estado coherente con polarización ortogonal al primero: hallamos que estos estados violan nuestra desigualdad siempre que nos encontremos dentro del tiempo de coherencia del estado de vacío comprimido. Cuantificamos también el entrelazamiento entre las parejas de fotones calculando la concurrencia de la matriz de densidad reducida de dos fotones: observamos que los estados que tienen mayor entrelazamiento satisfacen la condición para la visibilidad máxima de la interferencia entre bifotones. Hallamos también que la concurrencia es mayor para niveles de compresión menores, en acuerdo con la monogamia del entrelazamiento, siendo este resultado análogo al caso atómico. El trasladar estas desigualdades para los estados comprimidos en espín al dominio óptico nos permite observar directamente la relación entre estados comprimidos y entrelazamiento de manera experimental. Con este fin generamos un estado de vacío comprimido con un OPO y lo combinamos con un estado coherente para obtener un estado comprimido en polarización y contamos las parejas de fotones en diferentes bases de polarización. Con estas medidas reconstruimos las matrices de densidad que corresponden a diferentes versiones del estado comprimido en polarización usando tomografía cuántica: todas las matrices de densidad que hemos obtenido con este método están entrelazadas, mostrando valores de concurrencia de hasta 0.7. Nuestras medidas confirman las predicciones teóricas, entre las que se encuentra el entrelazamiento de todas las parejas de fotones dentro del tiempo de coherencia del estado entrelazado.

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Smith, Brian John. "Photon wave mechanics and experimental quantum state determination /." view abstract or download file of text, 2007. http://proquest.umi.com/pqdweb?did=1324388721&sid=1&Fmt=2&clientId=11238&RQT=309&VName=PQD.

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Thesis (Ph. D.)--University of Oregon, 2007.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 231-242). Also available for download via the World Wide Web; free to University of Oregon users.

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Morgan, Andrew Gordon. "Studies of final state photon radiation at LEP." Thesis, Durham University, 1994. http://etheses.dur.ac.uk/5952/.

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We consider two aspects of calculations involving the production of final state photons at LEP. The first addresses photons produced in association with hadrons. We motivate a measurement of the quark to photon fragmentation function and show how it can be used to account for isolated and non-isolated production rates. The second concerns the rare Z-decay to photons. We expose a subtle relationship between its various contributions. Following its investigation, we offer an improved method of calculation for weak processes at one loop.

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Carr, James. "Error analysis of X-ray photon correlation spectroscopy measurements." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117183.

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The use of a theory to extract parameters from experimental data requires proper understanding of the statistical variation. Furthermore, the improvement of any experimental technique requires a sound understanding of the sources of error and an accurate model of how experimental parameters effect signal strength and noise. The second order intensity-intensity correlation function is the standard measured quantity in dynamic light scattering and x-ray photon correlation spectroscopy (XPCS) experiments. In this thesis we compare the measured variances of the correlation function to a model based on the statistics of dynamic light scattering. Agreement between the dynamic light scattering model and the x-ray photon correlation spectroscopy data is shown. XPCS experiments are typically conducted with low photon flux and are used to study long time constants. To achieve sufficient statistics area detectors are used. We show that there are appreciable correlations between near neighbour pixels. These correlations reveal important features that must be included to accurately draw conclusions from XPCS experiments.
L'utilisation d'une théorie pour extraire des paramètres depuis des données expérimentales nécessite une compréhension des variations statistiques. De plus, l'amélioration d'une technique expérimentale repose sur la compréhension des sources d'erreurs and d'un modèle précis de l'effet des paramètres expérimentaux sur le signal et le bruit. La fonction de corrélation intensité-intensité de deuxième ordre est une quantité de mesure standardisée pour les expériences de diffusion de lumière dynamique et de spectroscopie de corrélation de photons en rayons X (X-ray Photon Correlation Spectroscopy, XPCS). Dans cette thèse, nous comparons les variances mesurées de la fonction de corrélation à un modèle basé sur les statistiques de diffusion de lumière dynamique. Nous démontrons l'accord entre le modèle de diffusion de lumière dynamique et les données XPCS. Les expériences XPCS sont en général effectuées avec un faible flux de photons et sont utilisées pourétudier les constantes à long terme. Pour atteindre des statistiques susantes, de détecteurs à résolution spatiale sont utilisés. Nous montrons l'existence de corrélations entre pixels voisins. Ces corrélations révèlent d'importantes caractéristiques qui doivent tre inclues afin de tirer des conclusions précises des expériences XPCS.

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White, Andrew James. "Photon-enhanced chemical vapour deposition of amorphous carbon thin films." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320045.

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Wang, Chunlang. "A Solid-State Single Photon Source Based on Color Centers in Diamond." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-72761.

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Wan, Noel H. (Noel Heng Loon). "Scalable creation of spin-photon interfaces for solid-state quantum information processing." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108979.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 61-64).
The negatively charged nitrogen vacancy (NV) defect center in diamond is a promising solid-state qubit due to its exceptional spin and optical properties. In this thesis, we develop high-yield, efficient spin-photon interfaces in diamond. In particular, we demonstrate a process that produces dielectic reflectors and photonic crystal nanobeam cavities directly on the surface of bulk diamond. Our results pave the way towards a scalable network of entangled quantum registers based on spin qubits in diamond.
by Noel H. Wan.
S.M.

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Engelkemeier, Melanie [Verfasser]. "Generation of multi-photon states by climbing the Fock ladder : quantum feedback and Fock-State generation / Melanie Engelkemeier." Paderborn : Universitätsbibliothek, 2021. http://nbn-resolving.de/urn:nbn:de:hbz:466:2-39606.

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Alqahtani, Moteb M. "Multi-photon processes in cavity QED." Thesis, University of Sussex, 2014. http://sro.sussex.ac.uk/id/eprint/49632/.

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Based on a multi-mode multi-level Jaynes-Cummings model and multi-photon resonance theory, a set of universal two-qubit and three-qubit gates has been realized where dual-rail qubits are encoded in cavities. In this way, the information has been stored in cavities and the off-resonant levels have been eliminated by the theory of an effective two-level Hamiltonian. A further model, namely the spin-J model, has been introduced so that a complete population inversion for levels of interest has been achieved and periodic multilevel multi-photon models have been performed. The combination of the two models has been employed to address two-level, three-level, four-level, and even five-level configurations. Considering the present cavity-QED experiments, several numerical simulations have been designed in order to check the robustness of the logic gates to variations in experimentally important parameters including the coupling constants and the detunings. Finally, based on Liouville's equation, and the wave-function treatments, the impact of decoherence processes on the fidelity of the qubit states in the iSWAP and the Fredkin gates has been studied. This thesis may have applications to quantum information processing, involving logic with simple quantum bits, with the possible application to the building of a quantum computer.

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Glover, Robert. "Search for two-photon emission from the first excited O+ State in 72Ge." Thesis, University of York, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487843.

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A new technique to investigate the phenomenon of two-photon emission in atomic nuclei has been developed and an experiment performed at the Chalmers University of Technology, Gothenburg. The long-lived first excited state in 7Â²GE was populated by the inelastic scattering of a pulsed neutron flux.

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Adeyemi, A. O. "Studies of interface dosimetry for photon energies below 1.25 MeV by thermally stimulated exoelectron emission." Thesis, University of Aberdeen, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333919.

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Following radiation excitation, exoelectrons which are emitted from the surface of a phosphor material on heating are produced from a depth of the order of ten nanometres thick. This permits the preparation of thin film TSEE dosimeters. The energies of these electrons are so small that only a multiplying device can be used to detect them. The study therefore involves building and developing a dosimetry system based on this principle. An energy band model has been used to describe the mechanism of exoelectron emission. The application of this model to experimental data shows that it can predict with accuracy the exoelectron energies and their frequencies of escape from traps which are eventually emptied by thermal stimulation. Deviations from theoretically predicted values are described and partially interpreted. A TSEE reader system has been developed which employs an electronic quenched gas-flow GM counter, ohmic regulated heating system and thermocouple for temperature measurements. The counting circuit is optimised for maximum pulse rate (25KHz for a resolution time of 40μsec), speed and minimum background electronic noise. The heating system can be controlled within 0.1°C/s - 10°C/s and the dosimeter actual temperature, accurately located to within ±2^oC. The whole set of TSEE data is accumulated on a BBC microcomputer. The most intense emitter, BeO was selected from among the commonly used exoelectron phosphors. The physical and chemical treatments of Na₂O and Li₂O doped thin film BeO which enhance TSEE dosimetry properties are considered. The description of preparation of the thin films is given. Characteristics of most importance to TSEE dosimetry obtained are as follows; a dose reproducibility within ±2.92&37, good linearity of response even from background level 10^-5Gy to 1Gy and an energy independence of response. The field in which this dosimetry system has proved very useful is in the study of interface dosimetry. It provides the necessary spatial resolution required for measurements in the steep dose gradient encountered between two dissimilar media of lead-; tin-; copper-; aluminium-; perspex; and carbon. From the results of measurements information can be gleaned about the finite dimensions of the interfaces for photon energies below 1.25MeV for which reliable information is scanty.

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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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Fulton, Roger. "Two-photon production of charmonium states /." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu148786754173099.

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Blankenship, Thomas Keith. "Rapidity gap in the final state hadron distribution in deep inelastic electron scattering at HERA." Diss., This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-06062008-170753/.

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Braunstein, Matthew McKoy Vincent McKoy Vincent. "Photoionization dynamics and ion state distributions in single-photon and resonance enhanced multiphoton ionization of molecules /." Diss., Pasadena, Calif. : California Institute of Technology, 1991. http://resolver.caltech.edu/CaltechETD:etd-06182007-133055.

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Zhang, Jie. "Control of Spin State Dynamics in Quantum Dot-Molecular Composites for Energy Multiplication." Kyoto University, 2021. http://hdl.handle.net/2433/261603.

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Stensson, Katarina. "Generation and detection of non-classical photon states." Licentiate thesis, KTH, Tillämpad fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-228058.

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This thesis intends to familiarize the reader with the concepts of photon statistics and correlations in quantum optics. Developing light sources that emit quantum states is central for the realization of quantum technologies. One important step in characterizing these sources is the measurement of field fluctuations and correlations, by coincidence measurements. The expectation value of a coincidence measurement, a simultaneous measurement of two intensities (or, more general, four fields), is represented by the fourth-order correlation function. The value of the correlation function, at zero delay between the detection of two photons, reveals important properties of the state to which they belonged, for example the fluctuations of the photon number. Since predictability is important for many applications, light sources emitting single photons are also characterized by the indistinguishability of consecutively emitted photons, or of two photons from separate emitters. In paper I we investigate blinking behaviour in quantum emitters, and its effect on the interference pattern and photon statistics with photons from two separate emitters. Blinking refers to an emitters transition into a non-emitting state, and subsequent transition back to an emitting state. We show that blinking can not be treated as linear loss, when measuring the fourth-order correlation function for two emitters in a Hong-Ou-Mandel setup. In general, a measurement of the fourth-order correlation function is robust to loss, which makes it a very practical tool. However, the relation between recorded coincidence counts and the correlation function is only direct in the limit of zero detection efficiency, and depends on the detection system. In paper II, we show that by adding a variable attenuation in the beam path, we can trace back to the ''true'' value of the correlation function at zero quantum efficiency. This method improves accuracy in correlation measurements by decreasing a systematic error at the expense of an increased statistical error, which is easier to handle, extending the use of coincidence methods to classical and non-classical multi-photon states.

QC 20180517

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Chamberlain, Martyn Paul. "Electrons, phonons, coupled phonon-plasmons and their interactions in semiconductor heterostructures." Thesis, University of Essex, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254491.

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Boddeda, Rajiv. "Absorptive optical non-linearities using Rydberg excitations in a Cavity." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLO021/document.

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Le contrôle des états quantiques de la lumière est une étape nécessaire pour la transmission et le traitement quantiques des informations. Un nuage d'atomes froids constitue un milieu optiquement non-linéaire très intéressant pour créer et manipuler des états photoniques. Le sujet de cette thèse est l'étude expérimentale de telles non-linéarités, induites entre des photons optiques par leur couplage avec des atomes de Rydberg. Les états de Rydberg sont des états atomiques très excités (n>30), qui permettent de créer des interactions photon-photon par l'intermédiaire de leurs interactions dipôle-dipôle à longue distance (>10µm). Nous utilisons une cavité de faible finesse pour transformer ces interactions en effets observables sur un faisceau de très faible intensité, ce qui peut permettre de produire des états non-classiques de lumière
The control of quantum states of light is a necessary step for quantum information transportation and processing. Cold atomic memories are one of the prime candidates for storing and manipulating photonic states. This thesis is a study of optical non-linear effects created using Rydberg states. Rydberg states are highly excited states (n>30) of atoms, which are useful in realizing photon-photon interactions because of their long distance (>10µm) dipole-dipole interactions. We utilize a low finesse cavity to transform phase shifts into intensity correlations which would allow one to generate arbitrary non-classical states of light

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Ryderfors, Linus. "Two-Photon Excited Fluorescence Depolarisation : Experimental and Theoretical Development." Doctoral thesis, Uppsala University, Department of Photochemistry and Molecular Science, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9285.

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We have studied fundamental aspects of time-resolved two-photon excited fluorescence depolarisation. The thesis presents experimental as well as theoretical progress. We show that a multi-photon induced instrumental response function obtained from a suspension of gold nanoparticles is appropriate for the analysis of two-photon excited fluorescence decays obtained using time-correlated single photon counting detection. Theoretical expressions have been derived for the fluorescence anisotropy decay obtained upon two-photon excitation of various molecular systems in liquid solutions: a) an anisotropic rigid rotor that undergoes rotational diffusion in the presence of ultrafast unresolved restricted reorientations, e.g. librations. b) a molecular group covalently attached to a stationary macromolecule, and undergoing local reorientation in a uniaxial ordering potential. A new approach to the analysis of two-photon excited fluorescence depolarisation experiments was developed, which combines data obtained by using linearly and circularly polarised excitation light, in a global manner. In the analysis, knowledge about unresolved reorientations was obtained from one-photon excitation studies of the corresponding systems. By means of this procedure it has been possible to obtain quantitative information about the molecular two-photon absorption tensor for perylene and two of its derivatives. Thereby the symmetry of the final excited and intermediate vibronic states could be assigned. The analysis reveals that the two-photon transition studied with the 800 nm laser exhibits mixed character. An important finding from the experiments was that the two-photon absorption tensor appears to be solvent dependent. Furthermore, the thesis presents the first theoretical treatment of two-photon excited donor-donor energy migration in the presence of molecular reorientation and which applies the extended Förster theory. Explicit expressions for molecules that belong to the point groups D_2h, D₂ and C_2v are given. Preliminary experiments are finally also reported on a two-photon excited donor-donor energy migration system consisting of a bisanthryl-bisteroid.

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Mosley, Peter James. "Generation of heralded single photons in pure quantum states." Thesis, University of Oxford, 2007. http://ora.ox.ac.uk/objects/uuid:44c36e1e-11ee-41e2-ba29-611c932ce4ff.

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Single photons - discrete wavepackets of light - are one of the most fundamental entities in physics. In recent years, the ability to consistently create and manipulate both single photons and pairs of photons has facilitated everything from tests of quantum theory to the implementation of quantum-enhanced precision measurements. These activities all fall within the scope of the rapidly-growing field of quantum information - the exploitation of the properties of quantum states (and specifically their capability to exist in superpositions) to accomplish tasks that would not be possible with classical objects. One stated goal of research in quantum information is to build a device consisting of a network of quantum logic gates that can evaluate quantum algorithms. The photonic implementation of individual logic gates has already been demonstrated. However, partly due to standard methods of preparing single photons, current schemes have severe limitations in terms of scaling up from a single logic gate to multiple concatenated operations. Until now it has not been proven that single photons can be generated in pure and indistinguishable quantum states, something upon which the successful operation of optical quantum logic gates relies. This thesis presents an experimental demonstration of simultaneous generation of almost identical single photons in highly pure states from two independent sources based on parametric downconversion. This is a process of photon pair generation during the passage of a light beam through a nonlinear crystal; one photon from the resulting pair is detected to herald the other. The work herein describes, refines, and implements a technique that minimises the strong quantum correlations usually present within each pair by spectral engineering of the source. This allows the heralded single photons to be in pure states, a property that is confirmed by observing a high-visibility two-photon interference effect without spectral filtering.

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Keyes, Robert. "New angular search for exotic physics in the photon+jet final state using the ATLAS detector on the LHC." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114367.

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This thesis outlines developments towards a new analysis and search technique for heavy resonances in angular distributions of photon+jet final states for the 2012 data set from the ATLAS detector on the LHC. In particular, a new angular variable tailored to the photon+jet channel was defined which distinguishes between background and expected signals, the corresponding angular observable sensitivity was optimized using ATLAS excited quark samples and JetPhox MC samples, and an optimal mass binning scheme was derived from the measured mass resolution. Ongoing work is being done to publish the analysis.
La présente thèse aborde le développement d'une nouvelle analyse et technique de recherche pour des resonances massives dans les distributions angulaires des états finaux dits photon+jet parmi les données récoltées en 2012 parle détecteur ATLAS du LHC. Une nouvelle variable angulaire développée sur mesure pour le canal photon+jet a d'ailleurs été définie afin de pouvoir distinguer le bruit de fond du signal plus efficacement. La sensitivité de cette observable a été optimisée en utilisant des échantillons Monte Carlo de quarks excités ainsi que du programme JetPhox. Une classification optimale en terme de masse a aussi été dérivée à partir de la mésure de la résolution de masse. Des travaux sont en course afin de publier l'analyse.

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Lyndon, Christopher Robinson. "Coincidence analyzing -power measurements of the reaction carbon(polarized proton,proton',photon)excited carbon through the 15.11 MeV state." W&M ScholarWorks, 1991. https://scholarworks.wm.edu/etd/1539623799.

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Analyzing-power measurements A$\sbsp{n}{coinc}$, A$\sbsp{s}{coinc}$, and A$\sbsp{l}{coinc}$ are presented for the reaction $\sp{12}$C($\vec p ,p\sp\prime\gamma$)$\sp{12}$C$\sp{\*}$ (15.11 MeV). A polarized proton beam at 318 MeV was used and data were taken for 3 mutually perpendicular directions of polarization. A scintillator hodoscope was used for scattered proton detection and 4 BGO detectors for the 15.11 MeV $\gamma$-ray. Data are presented for 8 azimuthal directions of the scattered proton around the beam direction, and for the polar angles averaged between 3.3$\sp\circ$ and 11.2$\sp\circ$. The data are compared with non-relativistic calculations (DW81) and relativistic calculations with explicit treatment of exchange (DREX). The average size of the asymmetries measured is comparable to these predictions but does not agree closely with either prediction.

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Melikechi, N. "The role of real intermediate states in two-photon absorption." Thesis, University of Sussex, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377074.

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Zheng, Zhan. "Two-photon--two-atom excitation with quantum multimode light states." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066589/document.

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Deux photons - deux atomes (2P2A) excitation s’avère être un banc de test importantde propriétés optiques quantiques. Depuis 1980, on sait que la probabilité de transition2P2A peut être grandement améliorée en utilisant la source monochromatique cohérenteavec la présence d’interactions atomiques qui induisent un pic de résonance de 2P2A. En2004 , Muthukrishnan et al. sont trouvés une grande amélioration de la transition ainsique d’une résonance de 2P2A, quand une source de deux photons intriqués, provenant dela radiation d’un atome cascade à trois niveaux, interagit avec les deux atomes différentsde l’ interaction. Leur conclusion est que : dans certaines situations, l’intrication peutremplacer un vrai hamiltonien d’interaction, qui est une déclaration de grande portée etune propriété importante liée à l’intrication. Ce phénomène mérite plus d’attention et defavoriser la compréhension
Two-photonÐtwo-atom (2P2A) excitation turns out to be an important test bench of quantum optical properties. In 2004, Muthukrishnan et al. announced a great enhancement of the transition at 2P2A resonance, when an entangled two-photon state, coming from a three-level cascade, interacts with two non-interacting atoms. Their conclusion: in some situations, entanglement can replace a real interaction Hamiltonian, reveals an important property related to entanglement. In this thesis, We study in detail the efficiency of various multimode two-photon states of light to induce the simultaneous excitation of two atoms of different kinds under 2P2A resonance condition. We find that several separable, correlated states, produced either by an atomic cascade or parametric down-conversion, or even appropriate combinations of coherent states, have comparable efficiencies as the photon state produced by an atomic cascade. We conclude that the true physical origin of the enhancement is the frequency anti-correlations, neither the temporal correlations, time ordering, nor entanglement. To present, we are not sure whether or not the enhancement is a quantum effect. We also studied: 1. the optimized 2P2A transition probability for a given photon spectrum; 2. the influence coming from finite lifetimes of the excited detecting atoms; 3. the 2P2A transition probability in the presence of atomic interaction

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Kitagawa, Akira. "Manipulation of Photon Number-States and Its Linear Optical Realization." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147620.

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Álvarez, Ruiz Jesús. "Photon induced fluorescence studies of molecules using synchrotron radiation." Licentiate thesis, KTH, Physics, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1567.

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This Licentiate thesis presents research accomplished at theSection of Atomic and Molecular Physics at the Royal Instituteof Technology in Stockholm using photon induced fluorescencespectroscopy (PIFS) during the last two years.

The main results presented are summarized:

- Neutral photodissociation in CO was observed aftersynchrotron photon excitation in the range 19-26 eV bycollecting dispersed fluorescence from excited neutral C atoms.Follow-up ab initio calculations point out CO Rydberg seriesconverging to the CO+ C and D states as precursors.

- The branching ratio between N2 + (B-X)(v=1,v=2) and (v=0,v=1)transitions in the 20-46 eV energy range reveals strongnon-Franck-Condon effects. Ab initio calculations indicate thatthe autoionization of certain superexcited states areresponsible for some of the structures present in the branchingratio curve, confirming the important role of non-Rydbergdoubly excited resonant states (NRDERS) in de-excitationprocesses above the ionization potential.

- Photon induced neutral dissociation processes in NO arereported. Neither Rydberg series nor other molecular states inNO known so far can account for the collected data. From abinitio calculations more information regarding the NO precursorstates and the mechanism behind the observed neutraldissociation were obtained.

- The details of a new experimental set-up for gas phasefluorescence measurements using synchrotron radiation aredescribed. It is able to perform simultaneous measurements ofdispersed and total fluorescence in the visible range. Thefirst results obtained with this set-up are presented,concerning fluorescence after excitation of the N2 molecules inthe N 1s edge.

These four studies conform the set of papers enclosed in theLicentiate thesis.

Finally a pre-study to further apply PIFS to speciespreviously excited by microwave discharge is included as futureplans.

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30

Armoogum, Daven Aidan. "Time resolved excited state photo-engineering." Thesis, University College London (University of London), 2004. http://discovery.ucl.ac.uk/1446477/.

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This thesis concerns the development and application of time resolved fluorescence which yield new and detailed information on molecular order and motion in both isotropic and ordered systems. Polarised fluorescence studies involve the photoselection of a non-equilibrium distribution of excited state probe orientations whose relaxation is monitored by time resolved fluorescence anisotropy. Chapter 1 introduces the basic concepts of probe photophysics and orientational photoselection. Chapter 2 combines photoselection with single and multiple laser pulses to provide a full description of probe alignment dynamics in the nematic phase of 5-cyanobiphenyl (5CB). In isotropic media the cylindrically symmetric and asymmetric alignment relaxation times are necessarily equal. However, in 5CB, this was seen to correlate strongly with equilibrium order parameters, indicating the need to quantify fully the probe orientational distribution function. In Chapter 3, single and two-photon time resolved fluorescence anisotropy measurements are used to determine the hitherto unmeasured (ground state) K=6 moment of P. The final chapters concern the development of the next generation of photoselection techniques where an excited state population is engineered by stimulated emission depletion (STED). In Chapter 4 STED following two-photon excitation (PUMP) has been demonstrated in a range of well established single photon probes and two recently developed quadrupolar chromophores. Saturation of the DUMP transition due to excited state re-pumping was investigated, and from a two level rate equation model stimulated emission cross-sections and ground state vibrational relaxation times were determined. In Chapter 5 the polarisation properties of STED are investigated; orientation-selective depletion was shown to yield highly polarised excited state arrays. Polarisation resolved STED measurements were shown to circumvent spontaneous emission selection rules (which forbid the measurement of excited state moments of rank K > 2) allowing the first measurements of hexadecapole (K=4) orientational relaxation in two fluorescent probes.

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31

Beyreuther, Elke. "Photon-assisted spectroscopy of electronic interface states in perovskite oxide heterostructures." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1198071350768-13837.

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Complex oxides are an intriguing field of solid-state research, as they can exhibit a wide variety of functional properties, such as ferroelasticity, ferroelectricity, ferro- and antiferromagnetism or an even more complicated type of magnetic ordering, the combination or interaction of those ferroic properties (multiferroicity), high spin polarization, or high-temperature superconductivity. Thus they are prospective candidates for future materials in microelectronics. It is a matter of fact that the performance of such oxide-based devices depends mainly on transport properties, which in turn depend on the distribution and density of intrinsic or extrinsic electronic interface states across the device structure. The present thesis focuses on the identification and characterization of such electronic properties by two different photoassisted spectroscopy techniques: surface photovoltage spectroscopy and photoelectron spectroscopy. This work especially deals with perovskite oxides, namely with the model perovskite strontium titanate (SrTiO3) as a substrate and three differently doped lanthanum manganite thin films (10-15 nm thickness) grown by pulsed laser deposition (PLD) on the SrTiO3 substrate(La0.7Sr0.3MnO3, La0.7Ca0.3MnO3, La0.7Ce0.3MnO3). The first part aims at the identification of electronic surface and interface states at the free SrTiO3 surface as well as at the three different lanthanum manganite/SrTiO3 interfaces. For that purpose three different experimental realizations of the surface photovoltage spectroscopy technique were implemented and employed: photoelectron spectroscopy under additional optical excitation, the capacitive detection of the photoinduced displacement current in a parallel-plate capacitor geometry under modulated optical excitation, and the classical Kelvin probe technique. The methods are evaluated comparatively with respect to their suitability to analyze the given oxidic interfaces. The main result of this first part is a map of the energetic positions and relaxation time constants of the surface states at the SrTiO3 surface as well as of the interface states at the lanthanum manganite/SrTiO3 interfaces within the SrTiO3 bandgap. The interface states were classified into film- and substrate-induced states and it could be demonstrated that an appropriate annealing procedure can dramatically decrease their densities. The second part tackles the problem of the manganese valence and the doping type of di- and tetravalent-ion-doped LaMnO3. The question whether the insulating parent compound LaMnO3 becomes an electron-doped semiconductor after doping with tetravalent cations such as Ce4+ - which would be in analogy to the well-established hole doping after partial substitution of La3+ by divalent cations such as Sr2+ or Ca2+ - has been discussed controversially in the literature so far. Due to the physics of the manganite crystal lattice the question can also be formulated in a different way: Can part of the manganese ions be driven from the Mn3+ state towards the Mn2+ state without any crystal instabilities or phase separation phenomena? In order to contribute to the clarification of this question, an extensive X-ray- and UV-photoelectron spectroscopy (XPS/UPS) investigation was performed. The three differently doped lanthanum manganite thin films were comparatively studied considering the exchange splitting of the Mn 3s core level line, which is a linear function of the Mn valence, as measured by XPS and the work function as extracted from UPS. All measurements were performed at different states of deoxygenation after heating in ultrahigh vacuum and reoxidation after heating in a pure oxygen atmosphere. Strong evidence for electron doping of the La0.7Ce0.3MnO3 film after deoxygenation was found. Furthermore, the reversible tunability of the Mn valence by variation of the oxygen content could be demonstrated for both tetravalent- and divalent-ion-doped lanthanum manganite films
Oxidische Komplexverbindungen können eine Vielzahl an funktionellen Eigenschaften, wie z.B. Ferroelastizität, Ferroelektrizität, Ferro- und Antiferromagnetismus sowie kompliziertere magnetische Ordnungen, die Kombination und Interaktion solcher ferroischer Eigenschaften (Multiferroizität), hohe Spinpolarisation oder Hochtemperatursupraleitung aufweisen und gelten daher als aussichtsreiche Materialien für die zukünftige Mikroelektronik. Entscheidend für die Funktionsfähigkeit oxidischer Bauelemente sind deren elektronische Transporteigenschaften, die in äußerst sensibler Weise von der Verteilung und Dichte von ex- oder intrinsischen elektronischen Defektzuständen an Grenz- und Oberflächen innerhalb der Bauelementstruktur abhängen. Die vorliegende Arbeit beschäftigt sich mit der Spektroskopie solcher elektronischer Eigenschaften mittels photonenbasierter Methoden. Im Fokus stehen dabei perowskitische Oxide , speziell das Modellperowskit Strontiumtitanat (SrTiO3) als Substrat und darauf mittels gepulster Laserdeposition (PLD) abgeschiedene dünne Filme (10-15 nm Dicke) dotierter Lanthanmanganate (La0.7Sr0.3MnO, La0.7Ca0.3MnO3, La0.7Ce0.3MnO3). Im Rahmen einer halbleiterphysikalischen Interpretation widmet sich der erste Teilder Identifikation elektronischer Ober- und Grenzflächenzustände an der SrTiO3-Oberfläche sowie an verschiedenen Lanthanmanganat/SrTiO3-Grenzflächen mittels dreier unterschiedlicher experimenteller Methoden zur Vermessung der Oberflächenphotospannung: der Photoelektronenspektroskopie unter zusätzlicher optischer Anregung, einer kapazitiven Detektionsmethode in Plattenkondensatorgeometrie unter modulierter optischer Anregung und der optischen Kelvin-Sonde. Neben einem auf die bei oxidischen Ober- und Grenzflächen auftretenden besonderen Herausforderungen zugeschnittenen Methodenvergleich werden Grenzflächenzustände bezüglich ihrer energetischen Position in der Bandlücke des SrTiO3 und ihres Relaxationsverhaltens analysiert, als substrat- oder filminduziert klassifiziert, und die Verringerung ihrer Dichte nach geeigneter Ausheilprozedur wird nachgewiesen. Der zweite Teil der Arbeit befasst sich mit der in der Literatur bisher kontrovers diskutierten Frage, ob sich die isolierende Stammverbindung LaMnO3 durch Dotierung mit tetravalenten Kationen, wie z.B. Ce4+, in einen elektronendotierten Halbleiter verwandeln lässt - analog zur Herstellung lochdotierter Lanthanmanganate durch Dotierung mit divalenten Kationen, wie z.B. Sr2+ oder Ca2+. Die Frage ist äquivalent zur Betrachtung, ob unter Beibehaltung der Stabilität des Kristallgitters ein Teil der Manganionen vom Mn3+-Zustand in den Mn2+-Zustand übergehen kann. Um einen Beitrag zur Klärung dieses Problems zu leisten, wurden als elektronisch sensitive Methoden die Röntgen- und UV-Photoelektronenspektroskopie (XPS/UPS) gewählt. Die oben genannten Lanthanmanganatfilme wurden dazu hinsichtlich der Austauschaufspaltung der Mangan-3s-Linie im XP-Spektrum, die in linearer Weise von der Manganvalenz abhängt, und der anhand der Breite des UP-Spektrums ermittelten Austrittsarbeit jeweils nach Reinigung der Oberfläche im Ultrahochvakuum (UHV) vergleichend untersucht. Die Messungen wurden nach unterschiedlich starker Desoxidation durch Heizen im UHV und Reoxidierung durch Heizen in Sauerstoffatmosphäre durchgeführt. Es konnte nachgewiesen werden, dass eine Elektronendotierung des La0.7Ce0.3MnO3-Films bei geeigneter Einstellung des Sauerstoffgehalts tatsächlich möglich ist. Außerdem wurde gezeigt, dass sich sowohl in di- als auch in tetravalent dotierten Lanthanmanganatfilmen die Manganvalenz und damit der Dotierungstyp reversibel durchstimmen lässt

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32

Reid, D. W. "A study of multi-particle states in photoproduction with photon beam energy 60 GeV to 170 GeV." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377471.

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33

Nishida, Sei. "Resting-state functional MR imaging identifies cerebrovascular reactivity impairment in patients with arterial occlusive diseases: A pilot study." Kyoto University, 2019. http://hdl.handle.net/2433/242403.

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34

Saaranen, Michael W. "Measuring the Radiative Lifetimes of the Vibrational Levels in the 6 sSg State of Sodium Dimers Using Time-Resolved Spectroscopy." Miami University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=miami1556890302820845.

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35

Sjödin, Marica. "Resonant multi-photon ionisation studies of high-energy states in small molecules." Doctoral thesis, KTH, Physics, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-409.

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This thesis describes separate studies of high-energy Rydberg and ion-pair states in small molecules using resonant multi-photon ionisation spectroscopy.

* OODR/REMPI study of ungerade Rydberg states in O₂

The energy region between 75000 and 99900 cm^-1 of O₂ has been studied using optical-optical double resonance (OODR) with resonance enhanced multi-photon ionisation (REMPI). Three-photon excitation via single rotational levels of the b(¹Σ⁺_g ) valence state was used to study np (n=3–10) and nf (n=4–9) Rydberg states converging on O₂⁺X(²Π_1/2,g) and X(²Π_3/2,g). The excitation pathway picks out non-predissociated states that are singlet in the (Λ,S) coupling scheme – suitable for np states for n ≥8, or are linear combinations of equal weight of singlet and triplet-spin states in the (Ω,ω) coupling scheme which was found to be suitable for nf states for all values of n.

* OTR/RI study of Rydberg and ion-pair states in I₂

Optical triple resonance (OTR) together with resonance ionisation (RI) has been used to study the ungerade manifold of molecular iodine between 57000 and 73000 cm^-1 via the E 0_g⁺(³P₂) ion-pair state. Two 6s Rydberg states with 0 +u symmetry based on excited states of the ion core have been observed.

During this study we also observed electric-field-induced mixing of nearly isoenergetic rovibrational levels of the E0_gP⁺(³P₂) and D0u+(³P₂) ion-pair states. Detectable mixing with an applied field of 1kV/cm occurs over a range of energy level separations of ≤0.3 cm^-1.

* (2+1)and (3+1) REMPI study of pyrrole (C₄H₅N) The two- and three-photon REMPI spectra of Rydberg states of pyrrole (C₄H₅N) have been recorded using circularly and linearly polarised light. The spectra were compared to the single-photon absorption spectrum of pyrrole and a similar study of furan (C₄H₄O). Although the ionisation spectra of pyrrole were considerably weaker than corresponding furan spectra, a strong propensity for excitation of d series with two photons and p and f series with three photons was observed for both molecules. The totally symmetric nd-Rydberg series associated with the first ionisation energy, [A₂]nd;A₁, was identified from n=3 to n=15 and extrapolated to obtain IE1.

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Sjödin, Marica. "Resonant multi-photon ionisation studies of high-energy states in small molecules /." Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-409.

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Sjödin, Marica. "Resonant multi-photon ionisation studies of high-energy states in diatomic molecules /." Stockholm, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-356.

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38

Matthiesen, Clemens. "Coherent photons from a solid-state artificial atom." Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/245821.

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Single spins confined in semiconductor quantum dots - artificial atoms in the solid-state - are attractive candidates for quantum mechanical bits, the fundamental units and building blocks of a quantum computer. The ability to address quantum dot spins optically allows us to initialise and manipulate the state of the quantum bit. Gaining information on the qubit, for example by reading out its state, not only requires state-selective optical excitation, but also access to the single photons scattered in response by the quantum dot. Further, for a distributed computer architecture where nodes of few quantum bits are interlinked via optical communication channels photonic quantum bits are required to faithfully transmit the quantum information. In this thesis we advocate resonant excitation of quantum dot transitions and collection of the resonance fluorescence to address two outstanding challenges: generating dephasing-free single photons for use as flying quantum bits and single-shot spin readout. To this end we investigate the spectral and first-order coherence properties of quantum dot resonance fluorescence. In particular, we directly observe highly coherent scattering in the low Rabi frequency limit which has remained unexplored for solid-state single photon emitters so far. At the same time, interactions with the semiconductor environment are revealed and quantified through their optical signatures: exciton-phonon coupling, nuclear spin dynamics and local electric field fluctuations signal a departure from the ideal atom-like behaviour. Taking advantage of the laser-like coherence of single phase-locked quantum dot photons in the Heitler regime, we demonstrate near-ideal two-photon quantum interference. This benchmark measurement is a precursor for the photonic entanglement of distant quantum dot spins in a quantum optical network, and the results here predict a high fidelity operation. Finally, moving to tunnel-coupled quantum dot molecules we show that the overlap of carrier wave functions in two closely spaced quantum dots forms new spin-selective optical transitions not available in single quantum dots. Then, the presence or absence of scattered photons reveals the electron spin. Intermittency in the quantum dot resonance fluorescence allowed us, for the first time, to observe spin quantum jumps in real-time. Both achievements - highly coherent photons and spin readout - provide the missing link to attempt creation of a small-scale quantum network now.

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39

Philip, George. "Two-photon spectra of Rydberg states of alkaline-earth atoms (strontium and barium)." Thesis, Open University, 2008. http://oro.open.ac.uk/54207/.

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The even-parity spectra of strontium and barium are very complex due to strong perturbation by several doubly excited configurations and this also increases discrepancies between theory and experiment in accurate level assignment and energy level and atomic structure data, particularly for the spectra of highly excited atoms and their behaviour in external fields and collisional processes which are of fundamental importance in the emerging applications in physics of cold atoms, quantum computing, precision atomic clocks and in the crossed-field problem. This thesis presents results from an experimental study to improve and extend the previously published observations in the two-photon spectra of the high-lying Rydberg states of SrI and Bal placed under a variety of test conditions such as external fields, collisions etc. Orthogonal excitation of a novel atomic jet in a purpose-built heat-pipe setup using a Xenon Chloride excimer laser pumped tunable narrow bandwidth dye laser and high sensitivity space-charge ionization in thermionic diode with complimentary optical detection was used for measurements. Presented are the two-photon spectra covering the dye laser wavelength (air) range of 460 - 425 nm for strontium and 495 - 467 nm for barium by which the J = 0,2 even-parity Rydberg series and autoionizing resonances just above the ionization limits labeled as; (4d²+5p²) ¹D₂ in strontium and 5d5f²p₁ in barium were observed. Original new energy level values are presented with substantial extension to the data in the literature for even-parity Rydberg series:

Sr I: 5sns ¹S₀ (12 < n < 46), 5snd ³D₂ (9 < n < 47) and 5snd ¹D₂ (9 < n < 82)

Ba I: 6sns ¹S₀ (13 < n < 68), 6snd ³D₂ (11 < n < 46) and 6snd ¹D₂ (11 < n < 88). New observation of certain anomalies including a Stark shift reversal effect and zero-field thermionic diode detection with remarkable sensitivity preserving all spectral features of Rydberg states is also presented. Controlled configuration mixing by exploiting electric field and collisions has allowed new observations for the two-photon forbidden odd-parity Rydberg series of SrI:

5s^{2 1}S₀ -> 5snp ¹P₁^o (32 < n < 46) and 5s^{2 1}S₀ -> 5snf ¹F₃⁰ (29 < n < 44). Extensive study of collision involving Rydberg atoms with neutral rare gas atoms has allowed to obtain new data for shift and broadening rates for Sr I series: 5sns ¹S₀ and 5snd ^1,3D₂ in the perturbed region which clearly exhibit Ramsauer effect. Collisional evolution of a remarkably broad resonance, labeled as 4d² ¹G₄, also exhibiting Ramsauer effect, is presented besides new level data for strontium 4d² ³P_J states accessed by two distinct processes- direct two-photon excitation and single-photon sequential excitation. Furthermore, the thesis presents the results of a novel experimental technique involving time-resolved gated pulsed field detection technique (GPT) employed for the first time to examine the time decay of Rydberg atoms yielding their effective lifetimes.

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40

Mondloch, Erin. "Quantum theory of conditional phonon states in a dual-pumped Raman optical frequency comb." Thesis, University of Oregon, 2017. http://hdl.handle.net/1794/22793.

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In this work, we theoretically and numerically investigate nonclassical phonon states created in the collective vibration of a Raman medium by the generation of a dual-pumped Raman optical frequency comb in an optical cavity. This frequency comb is generated by cascaded Raman scattering driven by two phase-locked pump lasers that are separated in frequency by three times the Raman phonon frequency. We characterize the variety of conditioned phonon states that are created when the number of photons in all optical frequency modes except the pump modes are measured. Almost all of these conditioned phonon states are extremely well approximated as three-phonon-squeezed states or Schrödinger-cat states, depending on the outcomes of the photon number measurements. We show how the combinations of first-, second-, and third-order Raman scattering that correspond to each set of measured photon numbers determine the fidelity of the conditioned phonon state with model three-phonon-squeezed states and Schrödinger-cat states. All of the conditioned phonon states demonstrate preferential growth of the phonon mode along three directions in phase space. That is, there are three preferred phase values that the phonon state takes on as a result of Raman scattering. We show that the combination of Raman processes that produces a given set of measured photon numbers always produces phonons in multiples of three. In the quantum number-state representation, these multiples of three are responsible for the threefold phase-space symmetry seen in the conditioned phonon states. With a semiclassical model, we show how this three-phase preference can also be understood in light of phase correlations that are known to spontaneously arise in single-pumped Raman frequency combs. Additionally, our semiclassical model predicts that the optical modes also grow preferentially along three phases, suggesting that the dual-pumped Raman optical frequency comb is partially phase-stabilized.

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41

Sontheimer, Bernd. "Characterization and Utilization of Novel Solid-State Quantum Emitters." Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/21465.

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In dieser Arbeit werden einzelne atomare Defekte in hexagonalem Bornitrid (hBN) charakterisiert und mögliche Anwendungen aufgezeigt, welche die gefundenen herausragenden optischen Eigenschaften ausnutzen. Solche optisch aktiven Punktdefekte in Halbleitern bergen das Versprechen von skalierbaren und stabilen Einzelphotonenquellen, welche für eine Vielzahl von zukünftigen Anwendungen im Bereich der Quanteninformationstechnologie oder für Präzisionsmessungen benötigt werden. Dementsprechend groß ist das Interesse der Wissenschaftsgemeinde, was sich auch in der Anzahl der untersuchten Defektsysteme widerspiegelt. Das Besondere an dem hier vorliegenden System ist zum einen die Zweidimensonalität des Halbleiter-Wirtskristalls und zum anderen die enorme Helligkeit des Emitters, welche sich in bis zu sechs Millionen mit einem Mikroskop detektierten Photonen pro Sekunde niederschlägt. Darüber hinaus motivieren die Stabilität des Emitters bei Raumtemperatur und die schmale spektrale Linienbreite eine tiefgreifende Analyse dieses Neuzugangs zum Emitterzoo.
In this thesis, single atomic defects in hexagonal boron nitride (hBN) are characterized and possible applications are shown, which take advantage of the outstanding optical properties found. Such optically active point defects in semiconductors hold the promise of scalable and stable single-photon sources, which are needed for a variety of future applications in quantum information technology or for precision measurements. The interest of the scientific community is correspondingly high, which is also reflected in the number of defect systems investigated. The special feature of the system presented here is on the one hand the two-dimensionality of the semiconductor host crystal and on the other hand the enormous brightness of the emitter, which is reflected in up to six million photons per second detected with a microscope. In addition, the stability of the emitter at room temperature and the narrow spectral width motivate a profound analysis of this new addition to the emitter zoo.

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Kabuß, Julia Verfasser], Andreas [Akademischer Betreuer] Knorr, and Oliver [Akademischer Betreuer] [Benson. "Solid state quantum optics : control of electrons, photons and phonons / Julia Kabuß. Gutachter: Andreas Knorr ; Oliver Benson." Berlin : Technische Universität Berlin, 2014. http://d-nb.info/106654655X/34.

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Kabuß, Julia [Verfasser], Andreas Akademischer Betreuer] Knorr, and Oliver [Akademischer Betreuer] [Benson. "Solid state quantum optics : control of electrons, photons and phonons / Julia Kabuß. Gutachter: Andreas Knorr ; Oliver Benson." Berlin : Technische Universität Berlin, 2014. http://d-nb.info/106654655X/34.

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44

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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Seri, Alessando. "A multimode solid-state quantum memory for single photons." Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/667262.

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Quantum memories (QMs) for light represent a fundamental ingredient for the development of a quantum internet. Among other applications, they are a building block for the distribution of entanglement on large scale, i.e. for the realization of a quantum repeater architecture. Rare earth doped crystals (REDCs) are a promising candidate towards this goal. In my thesis I use a Pr3+:Y2SiO5 crystal. The longest storage time and the highest retrieval efficiency for a solid-state memory measured so far, were demonstrated with this system (in the classical regime). However, the main advantages of solid-state platforms are their suitability for miniaturization and integration as well as their inhomogeneous broadening, which enables broadband storage and spectral multiplexing. In this thesis we demonstrate an on-demand solid-state QM for real single photons. Moreover we study new platforms for integrated QM based on the same material. We employ the atomic frequency comb (AFC) technique, which is the most promising storage protocol in terms of temporal multiplexing up to now. Until the start of my PhD there was still no demonstration of storage of a real quantum state of light with an on-demand readout in REDCs. We achieved this in the course of this thesis, measuring also for the first time (and only, at the time of writing) non-classical correlation between a single spin wave in a solid-state QM and a telecom photon. After proving the suitability of Pr3+:Y2SiO5 crystals for on-demand QMs, we demonstrated novel types of integrated optical memories based on the same system. We studied the spectroscopic and coherence properties of the ions in laser-written waveguides fabricated by fs-laser micromachining. These projects were developed in collaboration with Dr. R. Osellame and Dr. G. Corrielli at Politecnico di Milano, who fabricated the waveguides and analysed their guiding properties. In a first kind of waveguide, called type II, we performed the first storage with on-demand retrieval ever done in solid-state integrated optical memories (with classical light). We continued analysing a so-called type I waveguide, in which the mode-size is comparable with the mode guided in a single-mode fiber at the same wavelength. Here we showed storage of heralded single-photons for a pre-programmed time. The demonstrated storage time, 5.5 µs, is the longest quantum storage demonstrated in any integrated waveguide up to now. Finally, we performed in the same waveguide storage of the whole spectrum of a frequency-multiplexed heralded photon, spanning a range of frequencies of ˜ 4 GHz. The photon is naturally multiplexed due to the generation method used, namely cavity-enhanced SPDC. The possibility of storing such a broad spectrum comes from the intrinsic inhomogeneous broadening present in REDCs. Together with the 15 frequency modes constituting the multiplexed photon, 9 temporal modes were stored thanks to the intrinsic temporal multimodality of the AFC protocol. The method used to fabricate our waveguides, fs-laser micromachining, is the only one to our knowledge that allows for direct 3D fabrication in the substrate. In the future, this will yield matrices of fiber-pigtailed waveguide-based QMs, thus enabling a high degree of spatial multiplexing, which nowadays is mostly exploited in atomic clouds, where temporal and spectral multiplexing are more difficult to achieve. The crystal, the protocol and the waveguide fabrication technique employed in this thesis, represent all together a very promising system, opening the way for a future quantum repeater architecture based on scalable highly multiplexed QMs.
Les memòries quàntiques (MQs) per a la llum constitueixen un ingredient fonamental per al desenvolupament d’un Internet quàntic. Entre altres aplicacions, són un element bàsic per a la distribució de l’entrellaçament a llargues distancies, és a dir, per a la realització d’un repetidor quàntic. Els cristalls dopats amb terres rares (REDC) són candidats prometedors cap a aquest objectiu. En la meva tesi uso el cristall Pr3+:Y2SiO5. Amb aquest sistema (en el règim clàssic) es va demostrar el temps d’emmagatzematge més llarg i la major eficiència d’una memòria d’estat sòlid. No obstant això, els principals avantatges de les plataformes en estat sòlid són la possibilitat de miniaturització i integració, així com la ampliació inhomogènia dels seus perfils d’absorció, que permet emmagatzemar fotons amb banda ampla o multiplexats en freqüència. En aquesta tesi demostrem una MQ d’estat sòlid amb lectura on-demand per a fotons únics reals. A més, estudiem noves plataformes per a MQs integrades basades en el mateix material. Utilitzem la tècnica de pinta de freqüència atòmica (AFC), que és el protocol d’emmagatzematge més prometedor per a multiplexació temporal fins ara. Al començament del meu doctorat no hi havia cap demostració d’emmagatzematge d’un real estat quàntic amb una lectura on-demand del fotó en REDC. Ho hem aconseguit en el curs d’aquesta tesi, mesurant també per primera vegada (i única, en el moment d’escriure), una correlació no-clàssica entre una única ona de spin en una MQ d’estat sòlid i un fotó de telecomunicacions. Després de demostrar la idoneïtat dels cristalls Pr3+:Y2SiO5 com MQs, vam demostrar nous tipus de memòries òptiques integrades basades en el mateix sistema. Vam estudiar les propietats espectroscòpiques i de coherència dels ions en guies d'ones escrites amb làser fabricades amb la tècnica del fs-làser micromachining. Aquests projectes van ser desenvolupats en col·laboració amb el Dr. R. Osellame i el Dr. G. Corrielli del Politècnic de Milà, que van fabricar les guies d'ones i van analitzar les seves propietats orientadores. En un primer tipus de guia d'ona, anomenada tipus II, vam realitzar el primer emmagatzematge amb lectura on-demand mai realitzada en memòries òptiques integrades en estat sòlid (amb llum clàssica). Després vam analitzar un altre tipus de guia d’ondes anomenada tipus I, en la qual la mida del mode és comparable amb el mode guiat en una fibra monomode a la mateixa longitud d’ona. Aquí vam mostrar l’emmagatzematge de fotons simples durant un temps preprogramat. El temps d’emmagatzematge demostrat, de 5.5 µs, és fins ara l'emmagatzematge quàntic més llarg demostrat en qualsevol guia d'ones integrada. Finalment, es va realitzar en la mateixa guia l’emmagatzematge de tot l'espectre d'un bi-fotó multiplexat en freqüència, abastant un rang de freqüències de ˜4 GHz. El fotó és multiplexat de forma natural gracies al mètode de generació utilitzat, és a dir, el SPDC millorat per cavitat. La possibilitat d’emmagatzemar un espectre tan ampli prové de l’ampliació intrínseca de l’absorció inhomogènia present en els REDC. Juntament amb els 15 modes de freqüència que constitueixen el fotó multiplexat, s'han emmagatzemat 9 modes temporals gràcies a la multimodalitat temporal intrínseca del protocol AFC. El mètode utilitzat per fabricar les nostres guies d'ona, fs-làser micromachining, és l'únic que coneixem que permet directament fabricar en 3D en el substrat. En el futur, això donarà matrius de MQs basades en guies d’onades integrades con fibres, que permetran un alt grau de multiplexació espacial, que avui en dia s’explota sobretot en núvols atòmics, on el multiplexatge temporal i espectral és més difícil d’aconseguir. El cristall, el protocol i la tècnica de fabricació de guies d'ona utilitzats en aquesta tesi, representen tots junts un sistema

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47

Gündoğan, Mustafa. "Solid-state quantum memory for photonic qubits." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/322551.

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Optical quantum memories (QMs) are one of the fundamental building blocks in quantum information science (QIS). They might find important use in quantum communication and computation applications. Rare-earth ions (REIs) have been investigated for decades for their optical properties. They exhibit excellent coherence properties when cooled down to cryogenic temperatures. Not surprisingly, they emerged as a promising candidate for use in QIS as QMs. In this thesis, we investigated the quantum storage of photonic qubits in a Pr3+ :Y2SiO5 (PrYSO) crystal for potential use in quantum communication and networking applications. We started by constructing the experimental setup and the laser system from scratch as our research group had just been established at the beginning of this PhD study. First experiments included spectroscopy of the PrYSO system in order to identify the electronic transitions that are suitable for the QM experiments. We used the atomic frequency comb (AFC) memory protocol in all the experiments presented in this thesis. We also developed complex pulse sequences that are necessary for the optical preparation of an AFC. As a first experiment, we demonstrated the storage of photonic polarization qubits encoded in weak coherent states in the excited states of Pr3+ ions for a predetermined storage time of 500 ns. This had not been achieved previously due to the polarization dependent absorption of the material. We achieved average storage fidelities of ~95% which surpass the best achievable value with a measure and prepare strategy, thus proving the quantum character of our interface. Nevertheless, in order to be implemented in realistic quantum networking architectures, a QM should have the capability of on-demand retrieval of the stored information. As a first step towards this goal, our next experiment concerned the transfer of the input pulses to and from the long-lived hyperfine ground levels of Pr3+ ions, albeit with bright pulses. Furthermore, by performing time-bin interference experiments, we demonstrated that the coherence is preserved during the storage, transfer and retrieval processes. Temporal multimode storage in the spin-states up to 5 modes was also shown. Finally, in the last part of this thesis we demonstrated a solid-state spinwave quantum memory, with qubits encoded in weak coherent states at the single photon level. Storing and retrieving single-photon level fields in the ground levels of the PrYSO system is challenging as the strong control pulses and the weak input pulse to be stored in the memory are separated by only 10:2 MHz. The control pulses create noise, mostly as free-induction decay, fluorescence and scattering off the optical surfaces. In order to circumvent this problem we employed narrow-band spectral, temporal and spatial filtering. By using spectral-hole burning based narrow band filter created in a second PrYSO crystal, we could achieve signal-to-noise ratio (SNR) > 10 for input pulses with mean photon number of around 1. The high SNR we achieved allowed us to store and recall time-bin qubits with conditional fidelities again higher than that is possible with a measure and prepare strategy. This experiments also represents the first demonstration of a quantum memory for time-bin qubits with on demand read-out of the stored quantum information. The results presented in this thesis fill an important gap in the field of solid-state quantum memories and open the way for the long-lived storage of non-classical states of light. They further strengthen the position of REI based systems in QIS, specifically as nodes in scalable quantum network architectures.
Les memòries quàntiques òptiques (MQs) son un dels elements fonamentals en la ciència de la informació quàntica (CIQ). El seu ús podria ser important en aplicacions relacionades amb la comunicació i la computació quàntiques. Els ions de terres rares (ITRs) han sigut investigats durant dècades per les seves propietats òptiques. Exhibeixen excel·lents propietats de coherència quan es refreden a temperatures criogèniques. Per tant, no es sorprenent que hagin emergit com a candidats per ser usats en la CIQ com a MQs. En aquesta tesis, hem investigat l'emmagatzematge quàntic de qubits fotònics en un cristall de Pr3+:Y2SiO5 (PrYSO) per al seu possible ús en aplicacions relacionades amb xarxes d'informació quàntiques. Vam començar construint el dispositiu experimental i sistemes làser des de zero, ja que el nostre grup de recerca acabava de néixer. Els primers experiments van incloure espectroscòpia del sistema de PrYSO per identificar les transicions electròniques més apropiades per als següents experiments de MQs. En tots els experiments vam utilitzar el protocol de memòria basat en una pinta de freqüències atòmiques (PFA). També vam desenvolupar complexes seqüències de polsos, necessàries per a la preparació òptica d'una PFA. En el primer experiment vam demostrar l'emmagatzematge de qubits fotònics de polarització codificats en estats coherents febles. Aquest emmagatzematge es va dur a terme en els estats excitats dels ions Pr3+ durant un temps d'emmagatzematge predeterminat de 500 ns. Aquesta fita no s'havia assolit abans degut a que l'absorció òptica del material depèn de la polarització llum. Vam aconseguir fidelitats d'emmagatzematge d'un 95% de mitjana les quals sobrepassen el millor valor que es pot aconseguir amb una estratègia de mesura i preparació provant per tant el caràcter quàntic de la nostra interfície. Per poder-se implementar de manera realista en xarxes quàntiques, una MQ hauria de tenir la capacitat de recuperar la informació en-demanda (en el moment que es desitgi). Com a primer pas, el nostre següent experiment va involucrar la transferència dels polsos d'entrada cap a i des de els nivells fonamentals hiperfins i longeus dels ions Pr3+, mitjançant polsos brillants. A més, duent a terme experiments d'interferència, vam demostrar que la coherència es preserva durant els processos d'emmagatzematge, transferència i recuperació. També vam demostrar l'emmagatzematge temporalment multimodal en els estats d'espín, de fins a 5 modes. En l'última part d'aquesta tesis vam demostrar una memòria quàntica d'estat sòlid basada en ones d'espín, amb qubits codificats en estats coherents febles al nivell d'intensitat de fotons individuals. Emmagatzemar i recuperar camps òptics al nivell de fotons individuals en estats fonamentals del sistema PrYSO és exigent perquè els potents polsos de control i el polsos dèbils d'entrada que s'emmagatzemen a la memòria estan separats per només 10.2 MHz. Els polsos de control creen soroll, la majoria consistent en decaïment de lliure inducció, fluorescència i dispersió en les superfícies òptiques. Per resoldre aquest problema vam utilitzar filtratge estret de banda en freqüència i també filtratges temporal i espacial. Utilitzant un filtre estret de banda basat el la crema de forats espectrals en un segon cristall de PrYSO, vam poder aconseguir una relació senyal soroll (RSS) > 10 per a polsos d'entrada amb un número mitjà de fotons al voltant de 1. L'alta RSS que vam aconseguir ens va permetre emmagatzemar i recuperar qubits de inteval-de-temps amb fidelitats condicionals més altes una altra vegada que el que és possible amb l'estratègia de mesura i preparació. Els resultats presentats omplen un buit important en el camp de les memòries quàntiques d'estat sòlid i obren la porta a l'emmagatzematge de llarga durada d'estats de llum no-clàssics. A més, enforteixen la posició dels sistemes de IQ basats en ITR, específicament com a nodes en arquitectures de xarxes quàntiques.

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Mischok, Andreas, Robert Brückner, Hartmut Fröb, Vadim G. Lyssenko, and Karl Leo. "Photonic lattices in organic microcavities: Bloch states and control of lasing." SPIE, 2015. https://tud.qucosa.de/id/qucosa%3A35053.

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Organic microcavities comprising the host:guest emitter system Alq3:DCM offer an interesting playground to experimentally study the dispersion characteristics of laterally patterned microlasers due to the broad emission spectrum and large oscillator strength of the organic dye. By structuring of metallic or dielectric sublayers directly on top of the bottom mirror, we precisely manipulate the mode structure and in fluence the coherent emission properties of the device. Embedding silver layers into a microcavity leads to an interaction of the optical cavity-state in the organic layer and the neighboring metal which red-shifts the cavity resonance, creating a Tamm-plasmon-polariton state. A patterning of the metal can in turn be exploited to fabricate deep photonic wells of micron-size, efficiently confining light in lateral direction. In periodic arrays of silver wires, we create a Kronig-Penney-like optical potential in the cavity and in turn observe optical Bloch states spanning over several photonic wires. We modify the Kronig-Penney theory to analytically describe the full far-field emission dispersion of our cavities and show the emergence of either zero- , π-, or 2π- phase-locking in the system. By investigating periodic SiO2 patterns, we experimentally observe stimulated emission from the ground and different excited discrete states at room temperature and are able to directly control the laser emission from both extended and confined modes of the photonic wires at room-temperature.

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Yilmaz, Umit Oktay. "The Polarization Properties Of The Final State Particles In The Rare Radiative B-meson Decay." Phd thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606100/index.pdf.

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A general analysis of the photon and lepton polarizations in the rare Bs &
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l+l- decay by using the most general model independent form of the effective Hamiltonian is presented. The total and the differential branching ratios for these decays, when photon is in the positive and negative helicity states, are studied. The sensitivity of "
photon polarization asymmetry"
and the longitudinal, transverse and normal polarization asymmetries of final state leptons, as well as lepton-antilepton combined asymmetries in Bs &
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l+l- decay to the new Wilson coefficients are also investigated. It is shown that all these physical observables are very sensitive to the existence of new physics beyond SM and their experimental measurements can give valuable information about it.

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50

McGuinness, Hayden James 1980. "The creation and frequency translation of single-photon states of light in optical fiber." Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/11259.

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xiii, 164 p. : ill. (some col.)
We explore the frequency translation of single-photon states of light and the creation of photon pairs by four-wave mixing in optical fiber. Frequency translation refers to changing the central frequency of a field, while photon pair creation refers to the creation of two individual photons at the same time. We demonstrate these effects in third-order nonlinear optical fiber. While both phenomena have previously been shown by three-wave mixing in second-order nonlinear media, there are compelling reasons to develop these tasks in third-order media. Most importantly, frequency translation in third-order material allows for the practical implementation of both small and large frequency shifts, while second-order material only practically allows for large shifts. Photon creation in third-order media often permits more flexible phase-matching conditions, allowing for the creation of a wider variety of quantum states than is often possible in second-order media. In our theoretical study of photon pair creation, we focus on the spectral correlations of the photon pairs. We pay particular attention to the creation of quantum states of high purity, where the photons are not spectrally correlated with one another. High purity photons are a requisite resource for several different quantum information processing applications, such as linear-optical quantum computing. We find that states with high purity can be realized with a minimal amount of spectral filtering. Experimentally, we study photon frequency translation in photonic crystal fiber. The central wavelength of the input photons was translated from 683 nm to 659 nm. We perform second-order intensity correlation measurements on both channels to demonstrate their quantum nature. This resulted in values of 0.21 ± 0.02 and 0.19 ± 0.05 for the 683-nm and 659-nm channels, respectively, demonstrating that those fields were dominated by their single-photon component. The efficiency at which the process occurred was 29 percent. Theoretically, we develop a Green function formalism to describe the translation process and develop a computational model to calculate the solution to the governing equations. Also, in a related experiment, we demonstrate classical frequency translation from 851 nm to 641 nm, a record translation in both wavelength and frequency, at an efficiency of 0.2 percent in a birefringent fiber.
Committee in charge: Dr. Daniel Steck, Chair; Dr. Michael Raymer, Advisor; Dr. Steven van Enk, Inside Member; Dr. Raghuveer Parthasarathy, Inside Member; Dr. Andrew Marcus, Outside Member

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Dissertations / Theses on the topic 'State of the photon'

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