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Title:

Experimental Observation, Characterization, and

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vorgelegt von

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The Pennsylvania State University CiteSeerX Archives

Year of Publication:

2012-06-21

Source:

http://edoc.ub.uni-muenchen.de/11038/1/Wieczorek_Witlef.pdf

http://edoc.ub.uni-muenchen.de/11038/1/Wieczorek_Witlef.pdf Minimize

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text

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en

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Practical methods for witnessing genuine multi-qubit entanglement in the vicinity of symmetric states

Practical methods for witnessing genuine multi-qubit entanglement in the vicinity of symmetric states Minimize

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The Pennsylvania State University CiteSeerX Archives

Year of Publication:

2012-11-21

Source:

http://arxiv.org/pdf/0903.3910v2.pdf

http://arxiv.org/pdf/0903.3910v2.pdf Minimize

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text

Language:

en

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Metadata may be used without restrictions as long as the oai identifier remains attached to it.

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Title:

Multi-Photon Entanglement

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Major efforts in quantum information science are devoted to the development of methods that are superior to the one of classical information processing, for example the quantum computer or quantum simulations. For these purposes, superposition and entangled states are considered a decisive resource. Furthermore, since the early days of quantum m...

Major efforts in quantum information science are devoted to the development of methods that are superior to the one of classical information processing, for example the quantum computer or quantum simulations. For these purposes, superposition and entangled states are considered a decisive resource. Furthermore, since the early days of quantum mechanics, entanglement has revealed the discrepancy between the quantum mechanical and the everyday life perception of the physical world. This combination of fundamental science and application-oriented research makes the realization, characterization, and application of entanglement a challenge pursued by many researchers. In this work, the observation of entangled states of polarization encoded photonic qubits is pushed forward in two directions: flexibility in state observation and increase in photon rate. To achieve flexibility two different schemes are developed: setup-based and entanglement-based observation of inequivalent multi-photon states. The setup-based scheme relies on multi-photon interference at a polarizing beam splitter with prior polarization manipulations. It allows the observation of a family of important four-photon entangled states. The entanglement-based scheme exploits the rich properties of Dicke states under particle projections or loss in order to obtain inequivalent multi-photon entangled states. The observed states are characterized using the fidelity and entanglement witnesses. An increase in photon rate is crucial to achieve entanglement of higher photon numbers. This holds especially, when photon sources are utilized that emit photons spontaneously. To this end, a new photon source is presented based on a femtosecond ultraviolet enhancement cavity and applied to the observation of the six-photon Dicke state with three excitations. The implemented schemes not only allow the observation of inequivalent types of entanglement, but also the realization of various quantum information tasks. In this work, the four-photon GHZ state has been used in a quantum simulation of a minimal instance of the toric code. This code enables the demonstration of basic properties of anyons, which are quasiparticles distinct from bosons and fermions. Further, the six-photon Dicke state has been applied for quantum metrology: It allows one to estimate a phase shift with a higher precision than by using only classical resources. Altogether, a whole series of experiments for observing inequivalent multi-photon entangled states can now be substituted by a single experimental setup based on the designs developed in this work. In addition to this new approach of photon processing, a novel photon source has been implemented, paving the way to realizations of applications requiring higher photon numbers. ; This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of the Ludwig-Maximilians-Universität München's products or services. Internal or personal use of this material is permitted. However, permission to reprint republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org. By choosing to view this material, you agree to all provisions of the copyright laws protecting it. Minimize

Publisher:

Ludwig-Maximilians-Universität München

Year of Publication:

2009-12-17

Document Type:

Dissertation ; NonPeerReviewed

Subjects:

Fakultät für Physik

Fakultät für Physik Minimize

DDC:

535 Light & infrared & ultraviolet phenomena *(computed)*

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Title:

Multi-qubit entanglement engineering via projective measurements

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So far, various multi-photon entangled states have been observed experimentally by using different experimental set-ups. Here, we present a scheme to realize many SLOCC-inequivalent states of three and four qubits via projective measurements on suitable entangled states. We demonstrate how these states can be observed experimentally in a single ...

So far, various multi-photon entangled states have been observed experimentally by using different experimental set-ups. Here, we present a scheme to realize many SLOCC-inequivalent states of three and four qubits via projective measurements on suitable entangled states. We demonstrate how these states can be observed experimentally in a single set-up and study the feasibility of the implementation with present-day technology. Minimize

Year of Publication:

2009-01-26

Document Type:

text

Subjects:

Quantum Physics

Quantum Physics Minimize

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Title:

Quantum entanglement and teleportation in pulsed cavity-optomechanics

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Entangling a mechanical oscillator with an optical mode is an enticing and yet a very challenging goal in cavity optomechanics. Here we consider a pulsed scheme to create Einstein-Podolsky-Rosen-type entanglement between a traveling-wave light pulse and a mechanical oscillator. The entanglement can be verified unambiguously by a pump-probe seque...

Entangling a mechanical oscillator with an optical mode is an enticing and yet a very challenging goal in cavity optomechanics. Here we consider a pulsed scheme to create Einstein-Podolsky-Rosen-type entanglement between a traveling-wave light pulse and a mechanical oscillator. The entanglement can be verified unambiguously by a pump-probe sequence of pulses. In contrast to schemes that work in a steady-state regime under a continuous-wave drive, this protocol is not subject to stability requirements that normally limit the strength of achievable entanglement. We investigate the protocol's performance under realistic conditions, including mechanical decoherence, in full detail. We discuss the relevance of a high mechanical Qf product for entanglement creation and provide a quantitative statement on which magnitude of the Qf product is necessary for a successful realization of the scheme. We determine the optimal parameter regime for its operation and show it to work in current state-of-the-art systems. ; Comment: 10 pages, 2 figures Minimize

Year of Publication:

2011-08-12

Document Type:

text

Subjects:

Quantum Physics ; Condensed Matter - Mesoscale and Nanoscale Physics ; Physics - Optics

Quantum Physics ; Condensed Matter - Mesoscale and Nanoscale Physics ; Physics - Optics Minimize

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535 Light & infrared & ultraviolet phenomena *(computed)*

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Title:

Experimental entanglement of a six-photon symmetric Dicke state

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We report on the experimental observation and characterization of a six-photon entangled Dicke state. We obtain a fidelity as high as 0.654$\pm$0.024 and prove genuine six-photon entanglement by, amongst others, a two-setting witness yielding -0.422$\pm$0.148. This state has remarkable properties; e.g., it allows obtaining inequivalent entangled...

We report on the experimental observation and characterization of a six-photon entangled Dicke state. We obtain a fidelity as high as 0.654$\pm$0.024 and prove genuine six-photon entanglement by, amongst others, a two-setting witness yielding -0.422$\pm$0.148. This state has remarkable properties; e.g., it allows obtaining inequivalent entangled states of a lower qubit number via projective measurements, and it possesses a high entanglement persistency against qubit loss. We characterize the properties of the six-photon Dicke state experimentally by detecting and analyzing the entanglement of a variety of multipartite entangled states. ; Comment: replaced with published version Minimize

Year of Publication:

2009-03-12

Document Type:

text

Subjects:

Quantum Physics

Quantum Physics Minimize

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Experimental observation of an entire family of four-photon entangled states

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A single linear optical set-up is used to observe an entire family of four-photon entangled states. This approach breaks with the inflexibility of present linear-optical set-ups usually designed for the observation of a particular multi-partite entangled state only. The family includes several prominent entangled states that are known to be high...

A single linear optical set-up is used to observe an entire family of four-photon entangled states. This approach breaks with the inflexibility of present linear-optical set-ups usually designed for the observation of a particular multi-partite entangled state only. The family includes several prominent entangled states that are known to be highly relevant for quantum information applications. ; Comment: 4 pages, 4 figures Minimize

Year of Publication:

2008-06-11

Document Type:

text

Subjects:

Quantum Physics

Quantum Physics Minimize

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Title:

Useful Multiparticle Entanglement and Sub-Shot-Noise Sensitivity in Experimental Phase Estimation

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We experimentally demonstrate a general criterion to identify entangled states useful for the estimation of an unknown phase shift with a sensitivity higher than the shot-noise limit. We show how to exploit this entanglement on the examples of a maximum likelihood as well as of a Bayesian phase estimation protocol. Using an entangled four-photon...

We experimentally demonstrate a general criterion to identify entangled states useful for the estimation of an unknown phase shift with a sensitivity higher than the shot-noise limit. We show how to exploit this entanglement on the examples of a maximum likelihood as well as of a Bayesian phase estimation protocol. Using an entangled four-photon state we achieve a phase sensitivity clearly beyond the shot-noise limit. Our detailed comparison of methods and quantum states for entanglement enhanced metrology reveals the connection between multiparticle entanglement and sub-shot-noise uncertainty, both in a frequentist and in a Bayesian phase estimation setting. ; Comment: 4 pages, 4 figures Minimize

Year of Publication:

2011-08-30

Document Type:

text

Subjects:

Quantum Physics

Quantum Physics Minimize

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Title:

Non-classicality thresholds for multiqubit states - numerical analysis

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States that strongly violate Bell's inequalities are required in many quantum informational protocols as, for example, in cryptography, secret sharing and the reduction of communication complexity. We investigate families of such states with a numerical method which allows to reveal non-classicality even without direct knowledge of Bell's inequa...

States that strongly violate Bell's inequalities are required in many quantum informational protocols as, for example, in cryptography, secret sharing and the reduction of communication complexity. We investigate families of such states with a numerical method which allows to reveal non-classicality even without direct knowledge of Bell's inequalities for the given problem. An extensive set of numerical results is presented and discussed. ; Comment: 8 pages, journal version Minimize

Year of Publication:

2010-05-04

Document Type:

text

Subjects:

Quantum Physics

Quantum Physics Minimize

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Title:

Fisher information and multiparticle entanglement

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The Fisher information $F$ gives a limit to the ultimate precision achievable in a phase estimation protocol. It has been shown recently that the Fisher information for a linear two-mode interferometer cannot exceed the number of particles if the input state is separable. As a direct consequence, with such input states the shot-noise limit is th...

The Fisher information $F$ gives a limit to the ultimate precision achievable in a phase estimation protocol. It has been shown recently that the Fisher information for a linear two-mode interferometer cannot exceed the number of particles if the input state is separable. As a direct consequence, with such input states the shot-noise limit is the ultimate limit of precision. In this work, we go a step further by deducing bounds on $F$ for several multiparticle entanglement classes. These bounds imply that genuine multiparticle entanglement is needed for reaching the highest sensitivities in quantum interferometry. We further compute similar bounds on the average Fisher information $\bar F$ for collective spin operators, where the average is performed over all possible spin directions. We show that these criteria detect different sets of states and illustrate their strengths by considering several examples, also using experimental data. In particular, the criterion based on $\bar F$ is able to detect certain bound entangled states. ; Comment: Published version. Notice also the following article [Phys. Rev. A 85, 022322 (2012), DOI: 10.1103/PhysRevA.85.022322] by Geza T\'oth on the same subject Minimize

Year of Publication:

2010-06-22

Document Type:

text

Subjects:

Quantum Physics

Quantum Physics Minimize

DDC:

539 Modern physics *(computed)*

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