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Universiteit Utrecht

1. Ballester Sánchez, Manuel Alberto. Estimation of quantum states and operations.

Degree: 2005, Universiteit Utrecht

The subject of this thesis, quantum estimation theory, is inspired by recent developments, both practical and theoretical, in the new field of quantum information and computation. The main task of quantum estimation theory, the subject of this thesis, is that given many identical copies of an unknown quantum system one wants to "guess" or estimate what the system is. This is done by performing an "optimal" measurement and analyzing the data obtained from it. A quantum state is represented by a density matrix. In some cases one does not need to know the whole density matrix, sometimes a partial characterization is enough. Chapter 2 of this thesis is about optimally estimating the spectrum, i.e. the eigenvalues, of a density matrix. This is useful, for example, for estimating the entanglement of a bipartite pure state. The results of chapter 2 tell us that one can optimally estimate bipartite entanglement with LOCC measurements on one of the two parties. Unitary operations transform density matrices to density matrices. They are the gates of quantum information processing. Suppose one has one such unitary operation but one does not know what it does. In order to characterize it one needs to know how it transforms any input state. In order to know how a particular state is transformed, one can prepare that state, feed it to the unitary many times, and measure the output. One state is, of course, not enough. It turns out that the unitary can be completely characterized with a finite set of states, this is known as quantum process tomography. Unfortunately, in many cases it is difficult to have available in the lab all the input states needed to perform quantum process tomography. It is here where entanglement comes to the rescue. One pair of maximally entangled qubits, where one of them is used as input for the unitary gate and the other is left untouched, is sufficient. All the information about the unknown gate is contained in the joint output state. This is the problem treated in chapter 3. Now the output state needs to be measured. Again, one could measure the two qubits separately (LOCC) or jointly (collective measurement). Is there anything to gain by performing joint measurements? The answer is yes, optimal collective measurements are at least 3 times more accurate than any LOCC measurement. Chapter 4 treats the problem of estimating commuting unitary gates. There it is shown that this extra information makes it unnecessary to use an entangled input state and to use collective measurements at the output. In chapters 3 and 4 it is assumed that only one copy of the unitary gate is available. If, however, more than one copy (say N ) are available at the same time one could use an N-fold entangled state as input. If no entanglement is used, classical statistics tells us that the error of the estimation is proportional to 1/√N. In the literature, it has been shown that by using an entangled state in the input one can achieve an error proportional to 1/N. However, this has been shown only for qubit gates.…

Subjects/Keywords: Wiskunde en Informatica; quantum estimation; entanglement estimation; estimation of unitaries; spectrum estimation

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

APA (6th Edition):

Ballester Sánchez, M. A. (2005). Estimation of quantum states and operations. (Doctoral Dissertation). Universiteit Utrecht. Retrieved from http://dspace.library.uu.nl:8080/handle/1874/7310

Chicago Manual of Style (16th Edition):

Ballester Sánchez, Manuel Alberto. “Estimation of quantum states and operations.” 2005. Doctoral Dissertation, Universiteit Utrecht. Accessed September 23, 2020. http://dspace.library.uu.nl:8080/handle/1874/7310.

MLA Handbook (7th Edition):

Ballester Sánchez, Manuel Alberto. “Estimation of quantum states and operations.” 2005. Web. 23 Sep 2020.

Vancouver:

Ballester Sánchez MA. Estimation of quantum states and operations. [Internet] [Doctoral dissertation]. Universiteit Utrecht; 2005. [cited 2020 Sep 23]. Available from: http://dspace.library.uu.nl:8080/handle/1874/7310.

Council of Science Editors:

Ballester Sánchez MA. Estimation of quantum states and operations. [Doctoral Dissertation]. Universiteit Utrecht; 2005. Available from: http://dspace.library.uu.nl:8080/handle/1874/7310


Pontifical Catholic University of Rio de Janeiro

2. DEBORA FREIRE MONDAINI. [en] TENSOR PRODUCT UNIVERSALITY AND COECKENULLS COMPOSITIONALITY THEOREM.

Degree: 2006, Pontifical Catholic University of Rio de Janeiro

[pt] O propósito deste trabalho é apresentar uma demonstração simplificada do Teorema da Composicionalidade de Coecke, o qual diz respeito ao processamento de informação quântica agregada a estados emaranhados hpartidos. Utilizando a propriedade da universalidade do produto tensorial em nossa prova, veremos que é possível considerar todos os estados relevantes como sendo estados-produto, o que torna a demonstração bem mais fácil. Apresentaremos ainda o processo de teleportação de estados quânticos, tão comentado nos dias de hoje, e verificaremos finalmente que tal processo é uma aplicação trivial do teorema de Coecke.

[en] The purpose of this work is to present a simplified demonstration of Co- ecke's Compositionality Theorem, which refers to the quantum information processing associated to n-partite entangled states. By using the universal property of the tensor product in our proof, we will see that is possible to consider all the relevant states as being product states, which turns the demonstration much easier. We will present also the teleportation process of quantum states, so called nowadays, and verify finally that such a process is a trivial application of Coecke's theorem

Advisors/Committee Members: GEORGE SVETLICHNY.

Subjects/Keywords: [pt] MECANICA QUANTICA; [en] QUANTUM MECHANICS; [pt] INFORMACAO QUANTICA; [en] QUANTUM INFORMATION; [pt] UNIVERSALIDADE; [en] UNIVERSALITY; [pt] EMARANHAMENTO; [en] ENTANGLEMENT; [pt] TELEPORTACAO; [en] TELEPORTATION

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

APA (6th Edition):

MONDAINI, D. F. (2006). [en] TENSOR PRODUCT UNIVERSALITY AND COECKENULLS COMPOSITIONALITY THEOREM. (Thesis). Pontifical Catholic University of Rio de Janeiro. Retrieved from http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8674

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):

MONDAINI, DEBORA FREIRE. “[en] TENSOR PRODUCT UNIVERSALITY AND COECKENULLS COMPOSITIONALITY THEOREM.” 2006. Thesis, Pontifical Catholic University of Rio de Janeiro. Accessed September 23, 2020. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8674.

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

MLA Handbook (7th Edition):

MONDAINI, DEBORA FREIRE. “[en] TENSOR PRODUCT UNIVERSALITY AND COECKENULLS COMPOSITIONALITY THEOREM.” 2006. Web. 23 Sep 2020.

Vancouver:

MONDAINI DF. [en] TENSOR PRODUCT UNIVERSALITY AND COECKENULLS COMPOSITIONALITY THEOREM. [Internet] [Thesis]. Pontifical Catholic University of Rio de Janeiro; 2006. [cited 2020 Sep 23]. Available from: http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8674.

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

Council of Science Editors:

MONDAINI DF. [en] TENSOR PRODUCT UNIVERSALITY AND COECKENULLS COMPOSITIONALITY THEOREM. [Thesis]. Pontifical Catholic University of Rio de Janeiro; 2006. Available from: http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8674

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

3. Bin Ngah, Lufti Arif. Synchronisation toute optique d’un réseau de communication quantique : All-optical synchronization for quantum networking.

Degree: Docteur es, Physique, 2015, Nice

Ce manuscrit expose le développement de ressources fondamentales pour les communications quantiques à longues distances basées sur les technologies des fibres optiques télécoms et des guides d'onde optiques non linéaires. Après une introduction générale sur les communications quantiques, cette thèse est structurée en trois parties principales. La première partie illustre le développement de deux sources pour la génération de paires de photons intriqués en polarisation et émis à une longueur d'onde télécom via conversion paramétrique spontanée (SPDC) dans des guides d'ondes non linéaires intégrés sur niobate de lithium périodiquement polarisé. Les sources s'appuient respectivement sur un accord de phase de type-II et un accord de phase de type-0 et sur des solutions de filtrage et d'interférométrie mises en place après le cristal non linéaire. Dans la seconde partie, sont discutées les réalisations de deux sources de photons uniques annoncés haut débit. La première s'appuie sur le multiplexage spatial sur puce de photons uniques annoncés. La seconde exploite le multiplexage temporel passif grâce à l'utilisation d'un laser télécom cadencé à 10 GHz. Enfin, nous présentons une approche tout-optique visant la synchronisation de sources distantes de paires de photons intriqués, agencées selon une architecture de type relais quantique distribué. Cette technique innovante repose sur l'utilisation d'un laser télécom impulsionnel en tant qu'horloge optique de référence. Cette horloge autorise la synchronisation de l'émission de paires de photons dans la bande C des télécoms en deux lieux distants. Des résultats préliminaires d'interférence à deux photons sont montrés et discutés.

This manuscript reports the development of fundamental resources for long distance quantum communication based on fibre telecom technology and non-linear optical waveguides. After a general introduction on quantum communication, the thesis is structured along three parts. The first part illustrates the development of two photonic polarization entanglement sources suitable for quantum networking. Both sources generate paired photons at telecom wavelength via spontaneous parametric down conversion (SPDC) in periodically poled lithium niobate waveguides (PPLN/W). They rely on type-II and type 0 phase matching, respectively. In the second part, two high quality heralded single photon sources are highlighted. The first one relies on on-chip generation and spatial multiplexing of heralded single photons towards achieving higher bit rates. The second one takes advantage of passive temporal multiplexing of a single SPDC process. Finally, an all-optical approach towards efficient and accurate synchronization of remote entangled photon pair sources within quantum relay architecture over long distances is presented. This particular synchronization technique highlights the use of ultra-fast picosecond pulsed telecom fiber laser, operating at 2.5 GHz repetition rate, acting as a master optical clock, enabling to accurately synchronize the emission of photon…

Advisors/Committee Members: Tanzilli, Sébastien (thesis director), D'Auria, Virginia (thesis director).

Subjects/Keywords: Communication quantique; Réseaux quantiques; Optique intégrée; Optique quantique; Guides PPLN; Intrication en polarisation; Source de photons uniques annoncés; Interférence quantique; Relais quantique; Quantum communication; Quantum networking; Integrated non-linear optics; Quantum optics; PPLN waveguides; Polarization entanglement; Heralded single photon source; Quantum interference; Quantum relay

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

APA (6th Edition):

Bin Ngah, L. A. (2015). Synchronisation toute optique d’un réseau de communication quantique : All-optical synchronization for quantum networking. (Doctoral Dissertation). Nice. Retrieved from http://www.theses.fr/2015NICE4141

Chicago Manual of Style (16th Edition):

Bin Ngah, Lufti Arif. “Synchronisation toute optique d’un réseau de communication quantique : All-optical synchronization for quantum networking.” 2015. Doctoral Dissertation, Nice. Accessed September 23, 2020. http://www.theses.fr/2015NICE4141.

MLA Handbook (7th Edition):

Bin Ngah, Lufti Arif. “Synchronisation toute optique d’un réseau de communication quantique : All-optical synchronization for quantum networking.” 2015. Web. 23 Sep 2020.

Vancouver:

Bin Ngah LA. Synchronisation toute optique d’un réseau de communication quantique : All-optical synchronization for quantum networking. [Internet] [Doctoral dissertation]. Nice; 2015. [cited 2020 Sep 23]. Available from: http://www.theses.fr/2015NICE4141.

Council of Science Editors:

Bin Ngah LA. Synchronisation toute optique d’un réseau de communication quantique : All-optical synchronization for quantum networking. [Doctoral Dissertation]. Nice; 2015. Available from: http://www.theses.fr/2015NICE4141

.