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You searched for subject:(Lindblad equations). Showing records 1 – 3 of 3 total matches.

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1. Amini, Hadis. Stabilisation des systèmes quantiques à temps discrets et stabilité des filtres quantiques à temps continus : Stabilization of discrete-time quantum systems and stability of continuous-time quantum filters.

Degree: Docteur es, Mathématique et automatique, 2012, Paris, ENMP

Dans cette thèse, nous étudions des rétroactions visant à stabiliser des systèmes quantiques en temps discret soumis à des mesures quantiques non-destructives (QND), ainsi que la stabilité des filtres quantiques à temps continu. Cette thèse comporte deux parties. Dans une première partie, nous généralisons les méthodes mathématiques sous-jacentes à une rétroaction quantique en temps discret testée expérimentalement au Laboratoire Kastler Brossel (LKB) de l'École Normale Supérieure (ENS) de Paris. Plus précisément,nous contribuons à un algorithme de contrôle qui a été utilisé lors de cette expérience récente de rétroaction quantique. L'expérience consiste en la préparation et la stabilisation à la demande d'états nombres de photons (états de Fock) d'un champ de micro-ondes au sein d'une cavité supraconductrice. Pour cela, nous concevons des filtres à temps-réel permettant d'estimer les états quantiques malgré des imperfections et des retards de mesure, et nous proposons une loi de rétroaction assurant la stabilisation d'un état cible prédéterminé. Cette rétroaction de stabilisation est obtenue grâce à des méthodes Lyapunov stochastique et elle repose sur un filtre estimant l'état quantique. Nous prouvons qu'une telle stratégie de contrôle se généralise à d'autres systèmes quantiques en temps discret soumis à des mesures QND. Dans une seconde partie, nous considérons une extension du résultat obtenu pour des filtres quantiques en temps discret au cas des filtres en temps continu. Dans ce but, nous démontrons la stabilité d'un filtre quantique associé à l'équation maîtresse stochastique usuelle découlant par un processus de Wiener. La stabilité signifie ici que la “distance”entre l'état physique et le filtre quantique associé décroit en moyenne. Cette partie étudie également la conception d'un filtre optimal en temps continu en présence d'imperfections de mesure. Pour ce faire, nous étendons la méthode utilisée précédemment pour construire les filtres quantiques en temps discret tolérants aux imperfections de mesure. Enfin,nous obtenons heuristiquement des filtres optimaux généraux en temps continu, dont la dynamique est décrite par des équations maîtresses stochastiques découlant à la fois par processus de Poisson et Wiener. Nous conjecturons que ces filtres optimaux sont stables.

In this thesis, we study measurement-based feedbacks stabilizing discrete-time quantum systems subject to quantum non-demolition (QND) measurements and stability of continuous-time quantum filters. This thesis contains two parts. In the first part, we generalize the mathematical methods underlying a discrete-time quantum feedback experimentally tested in Laboratoire Kastler Brossel (LKB) at Ecole Normale Supérieure (ENS) de Paris. In fact, we contribute to a control algorithm which has been used in this recent quantum feedback experiment. This experiment prepares and stabilizes on demand photon-number states (Fock states) of a microwave field in a superconducting cavity. We design real-time filters allowing estimation of the state despite…

Advisors/Committee Members: Rouchon, Pierre (thesis director).

Subjects/Keywords: Contrôle non-linéaire; Mesures quantiques non-destructives (QND); Électrodynamique quantique en cavité (CQED); Filtrage quantique; Équation de Lindblad; Contrôle stochastique; Non-linear control; Quantum non-demolition (QND) measurements; Cavity quantum electrodynamics (CQED); Quantum filtering; Lindblad equations; Stochastic control

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Amini, H. (2012). Stabilisation des systèmes quantiques à temps discrets et stabilité des filtres quantiques à temps continus : Stabilization of discrete-time quantum systems and stability of continuous-time quantum filters. (Doctoral Dissertation). Paris, ENMP. Retrieved from http://www.theses.fr/2012ENMP0056

Chicago Manual of Style (16th Edition):

Amini, Hadis. “Stabilisation des systèmes quantiques à temps discrets et stabilité des filtres quantiques à temps continus : Stabilization of discrete-time quantum systems and stability of continuous-time quantum filters.” 2012. Doctoral Dissertation, Paris, ENMP. Accessed April 06, 2020. http://www.theses.fr/2012ENMP0056.

MLA Handbook (7th Edition):

Amini, Hadis. “Stabilisation des systèmes quantiques à temps discrets et stabilité des filtres quantiques à temps continus : Stabilization of discrete-time quantum systems and stability of continuous-time quantum filters.” 2012. Web. 06 Apr 2020.

Vancouver:

Amini H. Stabilisation des systèmes quantiques à temps discrets et stabilité des filtres quantiques à temps continus : Stabilization of discrete-time quantum systems and stability of continuous-time quantum filters. [Internet] [Doctoral dissertation]. Paris, ENMP; 2012. [cited 2020 Apr 06]. Available from: http://www.theses.fr/2012ENMP0056.

Council of Science Editors:

Amini H. Stabilisation des systèmes quantiques à temps discrets et stabilité des filtres quantiques à temps continus : Stabilization of discrete-time quantum systems and stability of continuous-time quantum filters. [Doctoral Dissertation]. Paris, ENMP; 2012. Available from: http://www.theses.fr/2012ENMP0056

2. A. Smirne. NON-MARKOVIANITY AND INITIAL CORRELATIONS IN THE DYNAMICS OF OPEN QUANTUM SYSTEMS.

Degree: 2012, Università degli Studi di Milano

In the present thesis we investigate two basic issues in the dynamics of open quantum systems, namely, the concept of non-Markovianity and the effects of initial system-environment correlations in the subsequent reduced dynamics. In recent research, a great effort has been put into the study and understanding of non-Markovian features within the dynamics of open quantum systems. At the same time, quantum non-Markovianity has been defined and quantified in terms of quantum dynamical maps, using either a divisibility property or the behavior of the trace distance between pairs of reduced states evolved from different initial states. We investigate these approaches by means of several examples, focusing in particular on their relation with the very definition of non-Markov process used in classical probability theory. Indeed, the notion of non-Markovian behavior in the dynamics of the state of a physical system and the notion of non-Markov process are quite different and it will appear how the former represents sufficient, but not necessary condition with respect to the latter. In particular, we explicitly show that the above-mentioned divisibility property in the classical case is not, in general, equivalent to the Chapman-Kolmogorov equation, proper to Markov stochastic processes. Furthermore, by taking into account a bipartite open system, we emphasize how the presence of non-Markovian effects strongly depends on where the border between open system and environment is set. A second relevant topic investigated in this thesis concerns the dynamics of open quantum system in the presence of initial system-environment correlations. By means of the approach based on trace distance, we go beyond the usual assumption that the open system and the environment are initially uncorrelated. The trace-distance analysis provides a characterization of open-system dynamics relying on measurements on the open system only, without the need for any extra information about the total system or system-environment interaction. After an introduction to the general theoretical scheme, we report an all-optical experimental realization, in which the total system under investigation consists of a couple of entangled photons generated by spontaneous parametric down conversion and initial correlations are introduced in a general fashion by means of a spatial light modulator. Finally, we take into account the Jaynes-Cummings model, showing how trace distance establishes general connections between correlation properties of initial total states and dynamical quantities that characterize the evolution of the open system. Advisors/Committee Members: tutor: B. Vacchini, coordinatore: M. Bersanelli, VACCHINI, BASSANO MARIA, BERSANELLI, MARCO RINALDO FEDELE.

Subjects/Keywords: open quantum systems; quantum dynamical maps; master equations; non-Markovianity; measures of non-Markovianity; initial correlations; trace distance; generalized Lindblad structure; Settore FIS/02 - Fisica Teorica, Modelli e Metodi Matematici

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Smirne, A. (2012). NON-MARKOVIANITY AND INITIAL CORRELATIONS IN THE DYNAMICS OF OPEN QUANTUM SYSTEMS. (Thesis). Università degli Studi di Milano. Retrieved from http://hdl.handle.net/2434/168736

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Smirne, A.. “NON-MARKOVIANITY AND INITIAL CORRELATIONS IN THE DYNAMICS OF OPEN QUANTUM SYSTEMS.” 2012. Thesis, Università degli Studi di Milano. Accessed April 06, 2020. http://hdl.handle.net/2434/168736.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Smirne, A.. “NON-MARKOVIANITY AND INITIAL CORRELATIONS IN THE DYNAMICS OF OPEN QUANTUM SYSTEMS.” 2012. Web. 06 Apr 2020.

Vancouver:

Smirne A. NON-MARKOVIANITY AND INITIAL CORRELATIONS IN THE DYNAMICS OF OPEN QUANTUM SYSTEMS. [Internet] [Thesis]. Università degli Studi di Milano; 2012. [cited 2020 Apr 06]. Available from: http://hdl.handle.net/2434/168736.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Smirne A. NON-MARKOVIANITY AND INITIAL CORRELATIONS IN THE DYNAMICS OF OPEN QUANTUM SYSTEMS. [Thesis]. Università degli Studi di Milano; 2012. Available from: http://hdl.handle.net/2434/168736

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


RMIT University

3. Jeske, J. Spatially correlated decoherence: understanding and exploiting spatial noise correlations in quantum systems.

Degree: 2014, RMIT University

The challenge of making nano-scale quantum systems experimentally accessible is being overcome for an increasing diversity of systems by improved fabrication techniques and experimental control. Despite rapid progress, one of the main hindrances in all experiments is the difficulty of isolating the quantum system from the surrounding environment and its fluctuations. This experimental “noise” perturbs the quantum system, a process that is generally referred to as decoherence: the system slowly loses its distinguishing quantum features. In this thesis the effects of spatial correlations in the noise environment with a finite correlation length are investigated. The consequences for the experimental design of controlled quantum systems as well as the dynamics of solid state systems are presented. We utilize the Bloch-Redfield formalism, a Markovian master equation approach, which gives a close connection to the underpinning system-environment model. We show how to use this formalism to model any spatial correlation function of the noise environment. Using microscopic environmental models, several correlation functions are derived and their properties connected to the environmental parameters. Several phenomenological correlation functions are also studied and a mapping to the Lindblad master equation is presented, which provides a test of positivity for phenomenological models. For quantum transport through spin chains and networks, noise is generally detrimental. Spatial correlations however reduce the effect of dephasing noise and can reinstate the transport dynamics. The critical correlation length proves to be closely connected to the maximal packet width of one excitation in the transfer process. For dissipation noise, relaxation-free states emerge with spatial correlations. The decay of an excitation is therefore fundamentally modified into a fast decay towards an intermediate relaxation-reduced state and a subsequent decay to the ground state on a much longer time scale. In quantum metrology noise correlations have been observed in experiments with trapped ions, in which they limit the use of such experiments for metrology. Quantum advantage, i.e. a better precision scaling than the standard quantum limit has been proven impossible in the presence of uncorrelated Markovian noise only. We show that for certain optimized states the best possible quantum advantage, Heisenberg scaling, can be achieved in the presence of noise with a finite spatial decay of correlations. We furthermore identify how dephasing effects change and a topology dependence arises in strength with increasing correlation length for entangled states in a general way. Biological photosynthetic complexes have recently been found to potentially include quantum coherent dynamics, particularly in the process of transmitting an exciton from the point of creation to the reaction centre. We show how the formalism of spatially correlated decoherence adapts to this significantly different energy regime. Typical effects of decoherence in…

Subjects/Keywords: Fields of Research; quantum systems; quantum noise; decoherence; dephasing; relaxation; spatial correlations; noise correlations; Bloch-Redfield equations; master equations; Lindblad equations; Markovian dynamics; quantum metrology; spin chain; quantum transport; light-harvesting complexes; quantum ferromagnet

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Jeske, J. (2014). Spatially correlated decoherence: understanding and exploiting spatial noise correlations in quantum systems. (Thesis). RMIT University. Retrieved from http://researchbank.rmit.edu.au/view/rmit:160897

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Jeske, J. “Spatially correlated decoherence: understanding and exploiting spatial noise correlations in quantum systems.” 2014. Thesis, RMIT University. Accessed April 06, 2020. http://researchbank.rmit.edu.au/view/rmit:160897.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Jeske, J. “Spatially correlated decoherence: understanding and exploiting spatial noise correlations in quantum systems.” 2014. Web. 06 Apr 2020.

Vancouver:

Jeske J. Spatially correlated decoherence: understanding and exploiting spatial noise correlations in quantum systems. [Internet] [Thesis]. RMIT University; 2014. [cited 2020 Apr 06]. Available from: http://researchbank.rmit.edu.au/view/rmit:160897.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Jeske J. Spatially correlated decoherence: understanding and exploiting spatial noise correlations in quantum systems. [Thesis]. RMIT University; 2014. Available from: http://researchbank.rmit.edu.au/view/rmit:160897

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

.