Dissertations / Theses on the topic 'Quantum trajectorie'
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ALBARELLI, FRANCESCO. "CONTINUOUS MEASUREMENTS AND NONCLASSICALITY AS RESOURCES FOR QUANTUM TECHNOLOGIES." Doctoral thesis, Università degli Studi di Milano, 2018. http://hdl.handle.net/2434/602166.
Full textCampagne-Ibarcq, Philippe. "Quantum backaction and feedback in superconducting circuits." Thesis, Paris, Ecole normale supérieure, 2015. http://www.theses.fr/2015ENSU0011/document.
Full textThis thesis presents a series of experiments highlighting measurement back action and decoherence in a basic open quantum system, the superconducting qubit. These observations are enabled by recent advances in amplification close to the quantum limit using Josephson circuits. The information extracted from the system can then be used as input in quantum feedback. A stroboscopic projective readout is performed and a feedback loop is used to correct for detected errors, thus stabilizing an arbitrary predetermined state of the qubit. When monitoring continuously the environment of the qubit by heterodyne detection of its fluorescence, we reconstruct individual quantum trajectories during relaxation. Conditioning this detection to the outcome of a following projective measurement, we access the weak values of the fluorescence signal. Included in a continuous feedback loop, this detection is also used to stabilize an arbitrary state of the qubit. Finally, a last experiment witnesses quantum Zeno dynamics of a resonant microwave mode, entailed by its coupling to the qubit
Benoist, Tristan. "Open quantum systems and quantum stochastic processes." Thesis, Paris, Ecole normale supérieure, 2014. http://www.theses.fr/2014ENSU0006/document.
Full textMany quantum physics phenomena can only be understood in the context of open system analysis. For example a measurement apparatus is a macroscopic system in contact with a quantum system. Therefore any experiment model needs to take into account open system behaviors. These behaviors can be complex: the interaction of the system with its environment might modify its properties, the interaction may induce memory effects in the system evolution, ... These dynamics are particularly important when studying quantum optic experiments. We are now able to manipulate individual particles. Understanding and controlling the environment influence is therefore crucial. In this thesis we investigate at a theoretical level some commonly used quantum optic procedures. Before the presentation of our results, we introduce and motivate the Markovian approach to open quantum systems. We present both the usual master equation and quantum stochastic calculus. We then introduce the notion of quantum trajectory for the description of continuous indirect measurements. It is in this context that we present the results obtained during this thesis. First, we study the convergence of non demolition measurements. We show that they reproduce the system wave function collapse. We show that this convergence is exponential with a fixed rate. We bound the mean convergence time. In this context, we obtain the continuous time limit of discrete quantum trajectories using martingale change of measure techniques. Second, we investigate the influence of measurement outcome recording on state preparation using reservoir engineering techniques. We show that measurement outcome recording does not influence the convergence itself. Nevertheless, we find that measurement outcome recording modifies the system behavior before the convergence. We recover an exponential convergence with a rate equivalent to the rate without measurement outcome recording. But we also find a new convergence rate corresponding to an asymptotic stability. This last rate is interpreted as an added non demolition measurement. Hence, the system state converges only after a random time. At this time the convergence can be much faster. We also find a bound on the mean convergence time
Weber, Steven Joseph. "Quantum Trajectories of a Superconducting Qubit." Thesis, University of California, Berkeley, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3686046.
Full textIn quantum mechanics, the process of measurement is intrinsically probabilistic. As a result, continuously monitoring a quantum system will randomly perturb its natural unitary evolution. An accurate measurement record documents this stochastic evolution and can be used to reconstruct the quantum trajectory of the system state in a single experimental iteration. We use weak measurements to track the individual quantum trajectories of a superconducting qubit that evolves under the competing influences of continuous weak measurement and Rabi drive. We analyze large ensembles of such trajectories to examine their characteristics and determine their statistical properties. For example, by considering only the subset of trajectories that evolve between any chosen initial and final states, we can deduce the most probable path through quantum state space. Our investigation reveals the rich interplay between measurement dynamics, typically associated with wavefunction collapse, and unitary evolution. Our results provide insight into the dynamics of open quantum systems and may enable new methods of quantum state tomography, quantum state steering through measurement, and active quantum control.
Warszawski, Prahlad. "Quantum Trajectories For, and As, Understanding." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/24237.
Full textAvanzini, Francesco. "Quantum molecular trajectory and stochastic theories of quantum fluctuations." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3424724.
Full textLa teoria di Bohm è una formulazione della Meccanica Quantistica che caratterizza lo stato di un sistema quantistico attraverso sia la funzione d’onda, come la teoria standard, sia le coordinate (le posizioni) di tutte le particelle che evolvono nel tempo secondo traiettorie quantistiche continue. Inoltre, un ensemble statistico di tutte le possibile traiettorie, che deriva dall’impossibilità di conoscere la posizione iniziale di tutte le particelle, stabilisce l’esatta corrispondenza con la Meccanica Quantistica tradizionale. Da un punto di vista computazionale, la teoria di Bohm è stata impiegata in Chimica Fisica principalmente per sviluppare nuove strategie risolutive dell’equazione di Schrödinger o nuove approssimazioni semi-classiche della Meccanica Quantistica. Da un punto di vista teorico, la caratteristica più attraente della teoria di Bohm è quella di essere il contesto naturale per definire un mappa concettuale tra il formalismo quantistico e la nostra rappresentazione dei sistemi chimici. I sistemi chimici sono composti di molecole, ma l’idea stessa di molecola è associata ad una specifica posizione spaziale delle particelle, i.e., i nuclei degli atomi. La descrizione statistica della Meccanica Quantistica convenzionale, sulla base della sola funzione d’onda, è insufficiente per definire una chiara corrispondenza con questa immagine delle molecole. Infatti, i chimici fanno spesso affidamento alla Meccanica Classica per aggirare questa difficoltà della teoria quantistica standard. Tuttavia, se la posizione delle particelle è inclusa nel formalismo quantistico, così come fa la teoria di Bohm, la corrispondenza può essere definita in modo autoconsistente. In altre parole, la teoria di Bohm sembra essere il contesto formale idoneo per rappresentare quantisticamente le molecole e il loro moto. Comunque, la raffigurazione chimica dei sistemi molecolari corrisponde ad una singola traiettoria di Bohm dato che si assume implicitamente che i componenti delle molecole abbiano una specifica posizione spaziale indipendentemente dal fatto che essa sia nota o meno. Di conseguenza, si è sviluppata una metodologia quantistica che si basa sull’assunzione che una singola traiettoria di Bohm, cioè una traiettoria molecolare quantistica, descrive correttamente i sistemi molecolari e il moto molecolare. In primo luogo, viene esaminata la corrispondenza tra una singola traiettoria di Bohm e la Meccanica Quantistica convenzionale dato che si rinuncia all’ensemble di traiettorie. Si verifica che tale corrispondenza esiste attraverso un esperimento numerico e si dimostra formalmente che le proprietà statistiche di una singola traiettoria spiegano la descrizione probabilistica della Meccanica Quantistica. Una volta che la coerenza di questa metodologia è stata verificata, vengono esaminate accuratamente le sue previsioni. Per esempio, si prendono in considerazione le costanti del moto (come l’energia) associate all’evoluzione temporale delle particelle e il comportamento di semplici sistemi chimici, e.g., il moto vibrazionale di singole molecole che interagiscono con un campo esterno risonante. In questo modo, proprietà inaspettate del moto molecolare emergono naturalmente. In secondo luogo, si considera la sfida di descrivere sistemi a molti componenti (quali sono i sistemi chimici in condizioni ordinarie). È ben noto che il calcolo della traiettoria di Bohm e della funzione d’onda è molto costoso computazionalmente. Comunque, le proprietà statistiche della traiettoria di Bohm permettono di derivare teorie stocastiche per esaminare la dinamica di sistemi quantistici aperti, come qualche molecola (o qualche grado di libertà) interagente con l’ambiente (le altre molecole). Uno dei metodi stocastici sviluppati correla la dinamica della matrice densità ridotta, per i gradi di libertà di interesse, all’evoluzione delle corrispondenti coordinate di Bohm. In altre parole, l’equazione di Bohm, che determina la velocità delle particelle attraverso la funzione d’onda, è sostituita da un’equazione stocastica che approssima la velocità di un sott’insieme di coordinate attraverso la matrice densità ridotta. In questo modo, le fluttuazioni quantistiche indotte dall’ambiente sono prese in considerazione. Il vantaggio del metodo riguarda la sua capacità di descrivere i sistemi quantistici, compresi quelli aperti, in termini di una traiettoria quantistica. Questo potrebbe permettere la comprensione del moto molecolare durante un esperimento spettroscopico. Di particolare interesse è la possibilità di esaminare sistemi reattivi, come quelli in cui avvengono cambi conformazionali. Come è ben noto, le reazioni chimiche possono essere totalmente caratterizzate solo attraverso il moto delle particelle e in questa tesi viene definita esattamente una metodologia quantistica che fornisce una descrizione autoconsistente del moto molecolare.
Buercklin, Samuel Adam. "Optimal trajectories for fast quantum harmonic transport." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121733.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (pages 85-88).
The transport of atomic ions trapped within a harmonic potential arises necessarily in the course of building a trapped ion quantum computer. We may define this problem in terms of a differential equation and its corresponding boundary conditions to satisfy which are sufficient to guarantee the motional quantum state of the ion is unaltered. However, the solution space to this problem is uncountably large, and the various solutions differ in many qualitative and quantitative aspects. We present an easily-computed functional of transport trajectories with intuitively interpretable terms which may be used to compare solutions to the quantum harmonic transport problem, but does not require an expensive quantum-mechanical simulation of the ion dynamics. Furthermore, we prove the convexity of this cost function under easily satisfied conditions in a Fourier Series parameterization of the problem. We then numerically optimize the cost function to discover optimal trajectories for the quantum harmonic transport problem.
by Samuel Adam Buercklin.
S.M.
S.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
Koch, Werner. "Non-Markovian Dissipative Quantum Mechanics with Stochastic Trajectories." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-63671.
Full textKuipers, Jack Anton. "Correlated Trajectories in Semiclassical Approaches to Quantum Chaos." Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486392.
Full textSutcliffe, Julia H. "Quantum studies of molecular dynamics." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282566.
Full textLopreore, Courtney Lynn. "Recent applications of the quantum trajectory method." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3034933.
Full textDuprey, Quentin. "Valeurs Faibles, Trajectoires Faibles et Interferométrie." Thesis, Cergy-Pontoise, 2019. http://www.theses.fr/2019CERG1049.
Full textMeasurement theory, based on projective measurements, is a fundamental aspect of quantum mechanics. Weak measurements differ from standard projective measurements on which the elementary axioms of quantum physics are built. Although weak measurement framework is defined within standard quantum mechanics, its implications are still poorly understood. The thesis work is part of a broad reflexion that aims to understand the conceptual and practical implications of such a measurement and to understand it in the context of quantum theory.Chapter 1 is a detailed introduction to weak measurements and weak values. Next, we will study the "weak trajectories" in a two slit interferometer. In Chapter 3, we discuss the implications of a cancellation of a weak value with respect to the observation of weak trajectories in nested Mach-Zender interferometers. Finally, Chapter 4 deals with the theoretical and experimental criticisms in the literature of the effect of the Cheshire Cat that is defined in the framework of weak measurement
Hemphill, Patrick A. "Intensity auto- and cross-correlations and other properties of a 85Rb atom coupled to a driven, damped two-mode optical cavity." Oxford, Ohio : Miami University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1248371234.
Full textTilloy, Antoine. "Mesure continue en mécanique quantique : quelques résultats et applications." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEE010/document.
Full textThis thesis is devoted to the study of the quantum trajectories obtained from thetheory of continuous measurement in non relativistic quantum mechanics. New theoretical resultsas well as examples of applications are presented. On the theoretical front, we study mostly thelimit of «strong» measurement where we put forward the emergence of quantum jumps and quantumspikes, two phenomena we characterize in detail. Out of the strong measurement limit, weinvestigate a method to extract information from a register of qubits optimally. On the applicationfront, we introduce an original method to control quantum systems exploiting only the freedomof changing the measurement intensity and we explain the transition between a ballistic and adiffusive behavior in open quantum random walks; two byproduct of the theoretical study of thestrong measurement regime. We further study the problem of semi-classical gravity and show thatcontinuous measurement theory allows to construct a consistent model in the Newtonian regime.We eventually suggest possible extensions of the formalism to a posteriori estimation and hint atgeneralizations of the results for the strong measurement limit in the wider context of discreterepeated measurements. In the course of our presentation, we emphasize the link with other approachesto the theory of continuous measurement (parallels with stochastic filtering and collapsemodels in foundations) rather than aim for mathematical rigor
Oxtoby, Neil Paul. "Keeping it real': A Quantum Trajectory Approach to Realistic Measurement of Solid-State Quantum Systems." Thesis, Griffith University, 2007. http://hdl.handle.net/10072/365770.
Full textThesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Science
Full Text
Cotton, Stephen Joshua. "Symmetrical Windowing for Quantum States in Quasi-Classical Trajectory Simulations." Thesis, University of California, Berkeley, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3686249.
Full textAn approach has been developed for extracting approximate quantum state-to-state information from classical trajectory simulations which "quantizes" symmetrically both the initial and final classical actions associated with the degrees of freedom of interest using quantum number bins (or "window functions") which are significantly narrower than unit-width. This approach thus imposes a more stringent quantization condition on classical trajectory simulations than has been traditionally employed, while doing so in a manner that is time-symmetric and microscopically reversible.
To demonstrate this "symmetric quasi-classical" (SQC) approach for a simple real system, collinear H + H2 reactive scattering calculations were performed [S.J. Cotton and W.H. Miller, J. Phys. Chem. A 117, 7190 (2013)] with SQC-quantization applied to the H 2 vibrational degree of freedom (DOF). It was seen that the use of window functions of approximately 1/2-unit width led to calculated reaction probabilities in very good agreement with quantum mechanical results over the threshold energy region, representing a significant improvement over what is obtained using the traditional quasi-classical procedure.
The SQC approach was then applied [S.J. Cotton and W.H. Miller, J. Chem. Phys. 139, 234112 (2013)] to the much more interesting and challenging problem of incorporating non-adiabatic effects into what would otherwise be standard classical trajectory simulations. To do this, the classical Meyer-Miller (MM) Hamiltonian was used to model the electronic DOFs, with SQC-quantization applied to the classical "electronic" actions of the MM model—representing the occupations of the electronic states—in order to extract the electronic state population dynamics. It was demonstrated that if one ties the zero-point energy (ZPE) of the electronic DOFs to the SQC windowing function's width parameter this very simple SQC/MM approach is capable of quantitatively reproducing quantum mechanical results for a range of standard benchmark models of electronically non-adiabatic processes, including applications where "quantum" coherence effects are significant. Notably, among these benchmarks was the well-studied "spin-boson" model of condensed phase non-adiabatic dynamics, in both its symmetric and asymmetric forms—the latter of which many classical approaches fail to treat successfully.
The SQC/MM approach to the treatment of non-adiabatic dynamics was next applied [S.J. Cotton, K. Igumenshchev, and W.H. Miller, J. Chem. Phys., 141, 084104 (2014)] to several recently proposed models of condensed phase electron transfer (ET) processes. For these problems, a flux-side correlation function framework modified for consistency with the SQC approach was developed for the calculation of thermal ET rate constants, and excellent accuracy was seen over wide ranges of non-adiabatic coupling strength and energetic bias/exothermicity. Significantly, the "inverted regime" in thermal rate constants (with increasing bias) known from Marcus Theory was reproduced quantitatively for these models—representing the successful treatment of another regime that classical approaches generally have difficulty in correctly describing. Relatedly, a model of photoinduced proton coupled electron transfer (PCET) was also addressed, and it was shown that the SQC/MM approach could reasonably model the explicit population dynamics of the photoexcited electron donor and acceptor states over the four parameter regimes considered.
The potential utility of the SQC/MM technique lies in its stunning simplicity and the ease by which it may readily be incorporated into "ordinary" molecular dynamics (MD) simulations. In short, a typical MD simulation may be augmented to take non-adiabatic effects into account simply by introducing an auxiliary pair of classical "electronic" action-angle variables for each energetically viable Born-Oppenheimer surface, and time-evolving these auxiliary variables via Hamilton's equations (using the MM electronic Hamiltonian) in the same manner that the other classical variables—i.e., the coordinates of all the nuclei—are evolved forward in time. In a complex molecular system involving many hundreds or thousands of nuclear DOFs, the propagation of these extra "electronic" variables represents a modest increase in computational effort, and yet, the examples presented herein suggest that in many instances the SQC/MM approach will describe the true non-adiabatic quantum dynamics to a reasonable and useful degree of quantitative accuracy.
Clemens, James Peter. "Collective spontaneous emission in the framework of quantum trajectory theory /." view abstract or download file of text, 2003. http://wwwlib.umi.com/cr/uoregon/fullcit?p3102158.
Full textTypescript. Includes vita and abstract. Includes bibliographical references (leaves 129-135). Also available for download via the World Wide Web; free to University of Oregon users.
Oriols, Pladevall Xavier. "Quantum Monte Carlo simulation of tunnelling devices using wavepackets and Bohm trajectories." Doctoral thesis, Universitat Autònoma de Barcelona, 1999. http://hdl.handle.net/10803/5353.
Full textAlarcón, Pardo Alfonso. "Quantum many-particle electron transport in time-dependent systems with Bohmian trajectories." Doctoral thesis, Universitat Autònoma de Barcelona, 2011. http://hdl.handle.net/10803/42002.
Full textIt is known that at nanoscale regime we must deal with the many-particle problem in order to study electronic devices. In this scenario, the time-dependent many-particle Schrödinger equation is only directly solvable for very few degrees of freedom. However, there are many electrons (degrees of freedom) in any electron device. In this sense, many-particle quantum electron formalisms (such as time-dependent Density Functional Theory, Green's functions techniques or Quantum Monte Carlo techniques) have been developed in the literature to provide reasonable approximations to model many-particle electron transport. An alternative proposal has been developed by Dr. Oriols to decompose the N-particle Schrödinger equation into a N-single particle Schrödinger equation using Bohmian trajectories. Based on this proposal a general, versatile and time-dependent 3D electron transport simulator for nanoelectronic devices, named BITLLES (Bohmian Interacting Transport for non-equiLibrium eLEctronic Structures) is presented. The novelty of the BITLLES simulator is based on two points. First, it presents a many-particle quantum electron transport model taking into account explicitly the Coulomb and exchange correlations among electrons using Bohmian trajectories. Second, it provides full information of the all current distribution moments (i.e. DC, AC, fluctuations and even higher moments). We summarize the important contributions of this thesis to the development of BITLLES simulator. Thus, we introduce explicitly the exchange correlations among electrons. In this context, we show how exchange interaction is the final responsible for determining the total current across the system. We also present a new approximation to study many-particle systems with spin of different orientations. Some practical examples are studied taking into account the exchange interaction. To the best of our knowledge, it is the first time that the exchange interaction is introduced explicitly (imposing the exchange symmetry properties directly into the many-particle wavefunction) in practical electron transport simulators. We present the computation of the time-dependent total current in the high-frequency regime where one has to compute time-dependent variations of the electric field (i.e. the displacement current) to assure current conservation. We discuss the computation of the total (conduction plus displacement) current using Bohmian trajectories and the Ramo-Shockley-Pellegrini theorems. Different capabilities of BITLLES simulator such as AC and current fluctuations are presented for Resonant Tunneling Devices. We have used the BITLLES simulator to test a new type of nanoelectronic device designed to process signals at THz regime named Driven Tunneling Device. It is a three terminal device where the drain-source conductance is controlled by a gate terminal that can oscillate at THz frequencies. We also present practical examples on the functionality of this device such as rectifier and frequency multiplier. Finally, we have developed a numerical approximation to solve the Schrödinger equation using tight-binding model to improve the band structure description of the BITLLES simulator.
McNally, Douglas M. II. "A NEW ALGORITHM FOR THE TIME EVOLUTION OF QUANTUM TRAJECTORY SIMULATIONS AND PHYSICALLY MOTIVATED ERROR MODELS IN 1D QUANTUM CELLULAR AUTOMATA." Miami University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=miami1407344625.
Full textJacobs, Andrew. "Probe Spectra and Photon Statistics in a Weakly-Driven Cavity Optomechanical System." Miami University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=miami1344150680.
Full textSarno, Giorgio. "A numerical approach to spin foam models of quantum gravity." Thesis, Aix-Marseille, 2020. http://www.theses.fr/2020AIXM0231.
Full textSpin foam models provide a Lorentz-covariant definition of the dynamics of loop quantum gravity. They offer a background-independent and non-perturbative quantization of gravity, and in their semiclassical limit, they are related to discretized General Relativity. However, the analytic complexity of the models is such that key questions concerning their theoretical consistency and physical predictions are still open. In this thesis, I introduce a systematic framework to perform numerical computations in this domain, to go beyond the limitations of the analytical techniques. The thesis contains an introduction to spin foam theories from a theoretical and a numerical standpoint, in particular to the EPRL model. I then present four of the six papers I published during my Ph.D., where the numerical framework was used to study critical open problems in the field. These include the numerical study of the semiclassical limit of a 4-simplex, recovering its Regge action and confirming known analytical computations ; a study of non-simplicial spin foams to offer an insight into the continuum limit of the theory ; a new approach to investigate extended triangulations and their semiclassical limit. Applied to a particular transition amplitude, the new approach allowed me to recover geometrical configurations compatible with curved boundary data, and to argue against an important dispute in the literature referred to as flatness problem. These results open a window for calculations in spin foam theories and they provide a new path to address their still unresolved questions
Lees, Eitan Jacob. "Suppression of Collective Quantum Jumps of Rydberg Atoms due to Collective Spontaneous Emission from Atoms in Free Space." Miami University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=miami1438276591.
Full textCruz, Rodriguez Lidice. "Méthodes de dynamique quantique ultrarapide basées sur la propagation de trajectoires." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30254/document.
Full textIn this thesis different trajectory-based methods for the study of quantum mechanical phenomena are developed. The first approach is based on a global expansion of the hydrodynamic fields in Chebyshev polynomials. The scheme is used for the study of one-dimensional vibrational dynamics of bound wave packets in harmonic and anharmonic potentials. Furthermore, a different methodology is developed, which, starting from a parametrization previously proposed for the density, allows the construction of effective interaction potentials between the pseudo-particles representing the density. Within this approach several model problems are studied and important quantum mechanical effects such as, zero point energy, tunneling, barrier scattering and over barrier reflection are founded to be correctly described by the ensemble of interacting trajectories. The same approximation is used for study the laser-driven atom ionization. A third approach considered in this work consists in the derivation of an approximate many-body quantum potential for cryogenic Ar and Kr matrices with an embedded Na impurity. To this end, a suitable ansatz for the ground state wave function of the solid is proposed. This allows to construct an approximate quantum potential which is employed in molecular dynamics simulations to obtain the absorption spectra of the Na impurity isolated in the rare gas matrix
Saller, Maximilian A. C. "Sampling minimal, adaptive basis sets for multidimensional, nuclear quantum dynamics using simple, semi-classical trajectories." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/97217/.
Full textCILLUFFO, Dario. "(Un)conditioned open dynamics in quantum optics." Doctoral thesis, Università degli Studi di Palermo, 2021. http://hdl.handle.net/10447/500775.
Full textBaldwin, Charles H. "Cavity QED with Center of Mass Tunneling." Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1312237577.
Full textSilva, Fernando Luis Semião da. "Interações de sistemas físicos com aplicações em óptica e informação quântica." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277313.
Full textTese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica "Gleb Wataghin"
Made available in DSpace on 2018-08-06T16:53:55Z (GMT). No. of bitstreams: 1 Silva_FernandoLuisSemiaoda_D.pdf: 1615501 bytes, checksum: 370145b0056b0b8da7cf94fb9d01bc25 (MD5) Previous issue date: 2006
Resumo: A presente tese é dedicada à utilização de conhecidos sistemas quânticos em aplicações de interesse em óptica e informação quântica. Motivados pelos recentes avanços experimentais em sistemas formados por íons aprisionados interagindo com lasers e na eletrodinâmica quântica de cavidades, nós focamos grande parte de nossas propostas nestes sistemas. Mais especificamente, nós estudamos a interação de íons e campos quantizados na chamada eletrodinâmica quântica de cavidades com íons aprisionados. Neste contexto, iniciamos nossos trabalhos com uma proposta de geração de superposições mesoscópicas no movimento do íon. Uma vez que tais superposições são muito sensíveis à decoerência, incluímos perdas na cavidade para tratar uma situação mais realista. Através da observação de quantum jumps, ou fóton-contagens fora da cavidade, mostramos um esquema de geração de estados com características quânticas muito similares aos encontrados no caso da cavidade ideal, sem perdas. Neste aspecto, encontramos um modo de usar a dissipação a nosso favor, fato de grande interesse experimental devido às imperfeições dos espelhos reais. Apresentamos também uma proposta de implementação de uma interação do tipo Kerr em íons como uma alternativa ao uso de cristais não-lineares que apresentam baixíssima eficiência para esse tipo de efeito. Essa proposta abre novas possibilidades para o uso de íons em medidas não demolidoras e computação quântica. Nossos estudos na área de eletrodinâmica quântica com íons aprisionados terminam com a análise dos efeitos do movimento do íon na dinâmica das transições multi-fotônicas. Esse é um estudo mais fundamental e está relacionado com o entendimento da interação da radiação com a matéria. Na última parte desta tese são apresentados resultados sobre o uso de sistemas de muitos corpos para a distribuição de informação quântica. O objetivo de se estudar estes sistemas mais complexos é a busca de implementação de protocolos quânticos em larga escala. Neste sentido, poderíamos pensar numa cadeia de osciladores harmônicos acoplados como ocorre em sistemas típicos da física da matéria condensada. Em particular, nós estudamos como aumentar a eficiência na transmissão de emaranhamento nestas cadeias. Propusemos um esquema que funciona como um tipo de quantum data bus, ou ônibus quântico para transportar e distribuir emaranhamento com alta eficiência
Abstract: This thesis is concerned with the use of firmly established quantum systems for applications in quantum optics and quantum information. Having been driven by recent experimental advances in laser-manipulated trapped ions and cavity quantum electrodynamics, we concentrated more on proposals to be implemented in those systems. Being more specific, we have studied the interaction between trapped ions and quantized fields in the so-called cavity quantum electrodynamics with trapped ions. In this context, we began with a proposal to generate mesoscopic superpositions in the motion of the ion. Since these superpositions are extremely sensitive to decoherence, we have included cavity losses in order to make the situation slightly more realistic. We showed that the observation of quantum jumps, or photon detection outside the cavity, would generate quantum states with properties close to that generated in the ideal lossless case. In spite of the normally destructive effect of dissipation, we found a way to use it in our favor which turns out to be of great experimental importance due to always present mirror imperfections. We also showed how to mimic cross-Kerr nonlinearities in the cavity-ion system as a feasible alternative to the use of nonlinear crystals whose intensity of that non-linearity is too weak. This proposal opens up new possibilities for the use of trapped ions in non-demolition measurements and quantum computing. We finish our work in cavity electrodynamics with trapped ions with the study of the effect of the ionic motion on the dynamics of multiphotonic transitions. This is a more fundamental issue that is related to the understanding of matter-field interaction. In the last part of this thesis, we present results on the use of many-body systems for quantum information distribution. It was our goal to study more complex systems for the implementation of quantum protocols in large scale. In this sense, one could think of a chain of coupled harmonic oscillators as commonly found in condensed matter physics. Particularly, we dealt with the efficiency of entanglement transmission through the chain, trying to improve it. We ended up with a scheme which acts as a quantum data bus able to transport and distribute entanglement around quite efficiently
Doutorado
Física
Doutor em Ciências
Métillon, Valentin. "Tomographie par trajectoires d'états délocalisés du champ micro-onde de deux cavités." Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEE051.
Full textQuantum state estimation, or tomography, is a key component of quantum technologies, allowing to characterise quantum operations and to extract information on the results of quantum information processes. The usual tomography techniques rely on ideal, single-shot measurements of the unknown state. In this work, we use a new approach, called trajectory quantum tomography, where the quantum trajectory of each realization of the state is recorded through a series of measurements, including experimental imperfections and decoherence. This strategy increases the extracted amount of information and allows to build new measurements for a set of feasible measurements.Using the tools of cavity quantum eletrodynamics, we have prepared entangled states of microwave photons spread on two separated modes. We have then performed a trajectory tomography of these states, in a large Hilbert space. We have proved that this method allows to estimate the state, to develop faster strategies for extracting information on specific coherences of the state and to compute error bars on the components of the estimated density matrix
Alonso, Castaneda Jose Joaquin [Verfasser], and Eric [Gutachter] Lutz. "Thermodynamics along classical and quantum trajectories under feedback control / Jose Joaquin Alonso Castaneda ; Gutachter: Eric Lutz." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2017. http://d-nb.info/1150964367/34.
Full textHemphill, Patrick A. "Intensity Auto- and Cross-Correlations and Other Properties of a 85Rb Atom Coupled to a Driven, Damped Two-Mode Optical Cavity." Miami University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=miami1248371234.
Full textBenseny, Cases Albert. "Trapping and ionising atoms with light: wave and trajectory dynamics of quantum-optical processes." Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/129127.
Full textQuantum mechanics was born at the beginning of the twentieth century to account for facts that the physical models at the time could not explain. Since then, many different formalisms and interpretations for it have appeared, each one with its particularities that allow it to provide different solutions for some quantum problems or to help describe particular quantum systems. Simultaneously, the study of light has always followed closely the development of quantum physics: from its inception in Albert Einstein's description of the photoelectric effect to the development of laser sources. In fact, laser light has proven to be a very useful tool to induce, manipulate, and measure the quantum behaviour of matter. For instance, lasers have allowed for the development of techniques to cool down, trap, and manipulate individual neutral atoms. Atomic matter waves in optical, electric, and magnetic potentials have been used for both testing the principles of quantum mechanics and developing applications such quantum information processing or atomtronics, where the trapped atoms constitute the building blocks of coherent diode and transistor-like devices. On the other hand, the last fifty years have witnessed an almost exponential increase in the intensity of light sources. These developments have challenged physics to find a description for the basic processes of light-matter interactions, much more complex than Einstein's photoelectric effect, yielding effects such as above-threshold or multiphoton ionisation or the emission of high-order harmonic radiation. The starting point of this thesis is a historical account of the development of quantum mechanics, after which we present the two mathematical formalisms of quantum mechanics that we use: the standard interpretation, which allows to represent the wave dynamics of matter, and the de Broglie-Bohm interpretation, where the quantum dynamics are described in terms of trajectories. The thesis deals with two different quantum-optical systems, i.e., regarding the interaction of light and matter at the quantum level. The first system under investigation is the coherent manipulation of ultracold atoms trapped in optical potentials. In particular, we study the atomic analogue technique in triple-well optical potentials of the stimulated Raman adiabatic passage (STIRAP) quantum-optical technique. Thanks to the de Broglie-Bohm formalism, we show that the description of this transport for a single atom (or a Bose-Einstein condensate) requires relativistic corrections in certain parameter regimes corresponding to very slow realisations of the process. Furthermore, we present for the case of multiple atoms a technique to transport empty sites in a row of optical microtraps, and extend it to develop atomtronic devices to control the flow of atomic matter waves. The second system we study is the ionisation of hydrogen by ultrastrong light pulses. We have used de Broglie-Bohm trajectories to obtain information about the dynamics and to propose methods for the calculation of the above-threshold ionisation and harmonic-generation spectra in a simple one-dimensional model. We also study the ionisation dynamics of a hydrogen atom interacting with a light beam carrying orbital angular momentum in full three-dimensional calculations, showing that it is possible to transmit the orbital angular momentum of the light to the electron dynamics. The associated de Broglie-Bohm trajectories of the process give a very clear visualisation of the absorption of angular momentum by the electrons.
Vadapalli, Ravi K. "Accuracy study of a free particle using quantum trajectory method on message passing architecture." Master's thesis, Mississippi State : Mississippi State University, 2002. http://library.msstate.edu/etd/show.asp?etd=etd-11062002-142043.
Full textLolli, Jared. "Quantum Measurement and Feedback Control of highly nonclassical Photonic States." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC223/document.
Full textIn recent years, the field of quantum optics has thrived thanks to the possibility of controlling light-matter interaction at the quantum level.This is relevant for the study of fundamental quantum phenomena, the generation of artificial quantum systems, and for quantum information applications.In particular, it has been possible to considerably increase the intensity of light-matter interaction and to shape the coupling of quantum systems to the environment, so to realise unconventional and highly nonclassical states.However, in order to exploit these quantum states for technological applications, the question of how to measure and control these systems is crucial.Our work is focused on proposing and exploring new protocols for the measurement and the control of quantum systems, in which strong interactions and peculiar symmetries lead to the generation of highly nonclassical states.The first situation that we consider is the ultrastrong coupling regime in cavity (circuit) quantum electrodynamics.In this regime, it becomes energetically favourable to have photons and atomic excitations in the ground state, that is no more represented by the standard vacuum.In particular, in case of parity symmetry, the ground state is given by a light-matter Schrödinger cat state.However, according to energy conservation, the photons contained in these exotic vacua are bound to the cavity, and cannot be emitted into the environment.This means that we can not explore and control them by simple photodetection.In our work we propose a protocol that is especially designed to overcome this issue.We show that we can infer the photonic properties of the ground state from the Lamb shift of an ancillary two-level system.Another class of systems in which the fundamental parity symmetry leads to very unconventional quantum states is given by two-photon driven-dissipative resonators.Thanks to the reservoir engineering, it is today possible to shape the interaction with the environment to stabilize the system in particularly interesting quantum states.When a resonator (an optical cavity) exchanges with the environment by pairs of photons, it has been possible to observe the presence of optical Schrödinger cat states in the transient dynamics of the system.However, the quantum correlations of these states quickly decays due to the unavoidable presence of one-photon dissipation.Protecting the system against this perturbation is the goal of the parity triggered feedback protocol that we present in this thesis
Woldekristos, Habtom G. "Tripartite Entanglement in Quantum Open Systems." Miami University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=miami1250185666.
Full textTarbox, Grayson J. "Simulations of Electron Trajectories in an Intense Laser Focus for Photon Scattering Experiments." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5828.
Full textColijn, Caroline. "The de Broglie-Bohm Causal Interpretation of Quantum Mechanics and its Application to some Simple Systems." Thesis, University of Waterloo, 2003. http://hdl.handle.net/10012/1044.
Full textCayayan, Lyndon Mark D. "Collective Quantum Jumps of Rydberg Atoms Undergoing Two-Channel Spontaneous Emission." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1470410030.
Full textBotheron, Pierre. "Approches classique, quantique et bohmienne de la dynamique électronique de systèmes atomiques en champ fort." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14201/document.
Full textWe are interested in the electronic dynamic of atomic system under influence of a short and intense laser pulse or induced by impact of positively charged ion. We then proceeds in a deeper comparative study of classical and quantal description of these interactions. On the basis of this study, we developped a self-consistent quantum trajectory method, based on the hydrodynamical formulation of Bohm. This method allow to obtain very precise observable while retaining the illustrative character of classical trajectory method
Yip, Ka Wa. "Optical pumping of multiple atoms in the single photon subspace of two-mode cavity QED." Miami University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=miami1438288697.
Full textMazzoni, Michele. "Generalized hydrodynamics of a (1+1)-dimensional integrable scattering theory with roaming trajectories." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23209/.
Full textGrigolo, Adriano 1986. "Multiconfigurational trajectory-guided quantum dynamics with generalized coherent states = Dinâmica quântica multiconfiguracional guiada por trajetórias com estados coerentes generalizados." [s.n.], 2017. http://repositorio.unicamp.br/jspui/handle/REPOSIP/330489.
Full textTese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
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Resumo: Uma versão generalizada do método 'coupled coherent states' é desenvolvida para estados coerentes associados a grupos de Lie arbitrários. Em contraste com a abordagem original, restrita a funções de base gaussianas, o método estendido é adequado para propagação de estados quânticos de sistemas exibindo propriedades físicas destituídas de análogo clássico, tais como graus de liberdade de spin ou indistinguibilidade de partículas. A formulação para o caso de sistemas com um número fixo de partículas idênticas interagentes é examinada em detalhe, sendo este um caso relevante descrito em termos de estados coerentes do grupo especial unitário. A técnica é ilustrada com aplicações simples, envolvendo modelos de Hubbard bosônicos e fermiônicos. Diversos aspectos da implementação numérica são discutidos
Abstract: A generalized version of the coupled coherent states method for coherent states of arbitrary Lie groups is developed. In contrast to the original approach, which is restricted to frozen-Gaussian basis sets, the extended method is suitable for propagating quantum states of systems featuring non-classical physical properties, such as spin degrees of freedom or particle interchange symmetry. The formulation for the relevant case of number-conserving systems of interacting identical particles, most adequately described in terms of coherent states of the special unitary group, is studied in detail. The technique is illustrated with applications to simple Hubbard-like models for both bosons and fermions. Several aspects of the numerical implementation are discussed
Doutorado
Física
Doutor em Ciências
2011/20065-4
141338/2011-3
FAPESP
CNPQ
Collet, François. "Short scale study of 4-simplex assembly with curvature, in euclidean Loop Quantum Gravity." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4076/document.
Full textA study of symmetrical assembly of three euclidean 4-simplices in classical, Regge and quantum geometry. We study the geometric properties and especially the presence of curvature. We show that classical and Regge geometry of the assembly have curvature which evolves in function of its boundary parameters. For the quantum geometry, a euclidean version of EPRL model is used with a convenient value of the Barbero-Immirzi parameter to define the transition amplitude of the assembly and its components. A C++ code is design for compute the amplitudes and study numerically the quantum geometry. We show that a classical geometry, with curvature, emerges already at low spin. We also recognize the appearance of the degenerate configurations and their effects on the expected geometry
López, José G. "Theoretical studies of the dynamics and spectroscopy of weakly bound systems." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1127220592.
Full textJack, Michael Wong. "Non-Markovian Quantum Trajectories." 1999. http://hdl.handle.net/2292/2237.
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Coffey, Timothy Michael 1970. "Non-dynamical quantum trajectories." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-12-2235.
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Chou, Chia-Chun. "Analytical study of complex quantum trajectories." Thesis, 2009. http://hdl.handle.net/2152/ETD-UT-2009-05-36.
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Rowland, Bradley Allen 1979. "Complex quantum trajectories for barrier scattering." Thesis, 2007. http://hdl.handle.net/2152/3811.
Full textYen-JiunChen and 陳彥均. "Quantum Chaos Control by Complex Trajectories." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/23849657514169077641.
Full text國立成功大學
航空太空工程學系碩博士班
98
In recent years, analysis and control of quantum chaos is increasingly important, but the lack of the concept of trajectory makes it impossible to analyze quantum chaos by the methods used in classical chaos. The aim of this thesis is to connect the Newton’s world to the quantum world by the complex mechanics so that quantum chaos can be analyzed and controlled by the complex-extended Newtonian mechanics. Through the bridge of complex mechanics, in this thesis we model quantum motions for 2D charged anisotropic harmonic oscillator by complex-valued dynamic equations based on which quantum chaos can be analyzed by using well-known methods used in classical chaos. With the established quantum dynamic model, we then apply the sliding-mode control method to control the chaotic quantum behavior of the considered quantum system. The simulation results show that chaotic motions can be changed into periodic motions by the proposed chaos control and meanwhile, chaos synchronization can be achieved in the presence of variations of initial conditions. Several signatures of chaos are introduced here to justify the chaos to periodicity process under the sliding-mode control law.
Wei, Chia-Hung, and 魏嘉宏. "A Study on Quantum Chaos and Quantum Probability from the Viewpoint of Complex Quantum Trajectories." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/88220137415754845449.
Full text國立成功大學
航空太空工程學系碩博士班
97
On the basis of quantum Hamilton mechanics, several issues are addressed in this dissertation. First of all, we study the multi-path behavior of quantum systems by virtue of the complex trajectory interpretation of quantum mechanics. It is shown that Feynman’s path-integral trajectories can be represented by the complex trajectories and then parameterized within the framework of quantum Hamilton mechanics. Next, two simplified physical systems, a 1D harmonic oscillator and a 2D charged anisotropic harmonic oscillator in a uniform magnetic field, are demonstrated to exhibit chaos from the viewpoint of particle-like behavior. While conventional quantum mechanics and Bohmian mechanics both predict that 1D harmonic oscillator shows no signature of chaotic behavior, we find that in quantum Hamilton mechanics this system exhibits both regular and chaotic behavior, depending on the composition of wavefunctions and on the particle’s initial position. We continue to investigate chaotic behavior in a 2D charged anisotropic harmonic oscillator. Even the possibility of chaos in eigenstates has been ruled out from Bohm’s trajectory interpretation, we still find obvious chaotic features in eigenstates of this 2D quantum oscillator. The territory of quantum chaos indeed can be enlarged via the complex-extended dynamics. Finally, we point out that the complex chaotic dynamics may be the origin of the probability interpretation of quantum mechanics. In view of the generality of quantum chaos, it is impossible to predict the final states from the initial states for quantum systems. However, the statistical invariability of chaotic behavior offers another route for us to understand quantum systems. In this dissertation, the comparison between the distribution of complex quantum trajectories on the real coordinate space and the theoretic probability density function determined from the wavefunction shows that a chaotic quantum particle which seems to move irregularly is indeed guided by the wavefunction and attempts to appear somewhere with a statistical regularity. We also examine this tendency for Bohmian trajectories, however, no analogue of the complex trajectories can be found.