Distribution of entanglement in large-scale quantum networks

Perseguers, Sébastien; Lapeyre, G. J.; Cavalcanti, Daniel; Lewenstein, Maciej; Acín, Antonio

doi:10.1088/0034-4885/76/9/096001

Cited by 97 publications

(97 citation statements)

References 122 publications

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“…Iterations of a given generic time evolution step and assuming a countable number of different states of the system thus represents a large class of physical situations, including classical and quantum networks 5 . A generic way to represent a discretized iterative dynamical process, is a discrete time random walk on a graph, in both the classical and the quantum case.…”

Section: Introductionmentioning

confidence: 99%

Quantized recurrence time in unital iterated open quantum dynamics

et al. 2015

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The expected return time to the original state is a key concept characterizing systems obeying both classical or quantum dynamics. We consider iterated open quantum dynamical systems in finite dimensional Hilbert spaces, a broad class of systems that includes classical Markov chains and unitary discrete time quantum walks on networks. Starting from a pure state, the time evolution is induced by repeated applications of a general quantum channel, in each timestep followed by a measurement to detect whether the system has returned to the original state. We prove that if the superoperator is unital in the relevant Hilbert space (the part of the Hilbert space explored by the system), then the expectation value of the return time is an integer, equal to the dimension of this relevant Hilbert space. We illustrate our results on partially coherent quantum walks on finite graphs. Our work connects the previously known quantization of the expected return time for bistochastic Markov chains and for unitary quantum walks, and shows that these are special cases of a more general statement. The expected return time is thus a quantitative measure of the size of the part of the Hilbert space available to the system when the dynamics is started from a certain state.

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Section: Introductionmentioning

confidence: 99%

Quantized recurrence time in unital iterated open quantum dynamics

et al. 2015

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“…Up to now, only a few schemes, which distribute entanglement over the distance of 200 km using fiber-optic [4] and 100 km using free-space channel [5] between the nodes have been experimentally demonstrated. Nevertheless, motivated by a rapidly growing experimental and theoretical progress in the field of quantum communication, various quantum repeater schemes and single building blocks have been proposed [6], [7], [8], [9], [10], [11].…”

Section: Introductionmentioning

confidence: 99%

Quantum repeater based on cavity QED evolutions and coherent light

Gonţa¹,

Loock²

2016

Appl. Phys. B

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In the framework of cavity QED, we propose a quantum repeater scheme that uses coherent light and chains of atoms coupled to optical cavities. In contrast to conventional repeater schemes, we avoid the usage of two-qubit quantum logical gates by exploiting solely the cavity QED evolution. In our previous paper [D. Gonta and P. van Loock: Phys. Rev. A 88, 052308 (2013)], we already proposed a quantum repeater in which the entanglement between two neighboring repeater nodes was distributed using controlled displacements of input coherent light, while the produced low-fidelity entangled pairs were purified using ancillary (fourpartite) entangled states. In this paper, the entanglement distribution is realized using a sequence of controlled phase shifts and displacements of input coherent light. Compared to previous coherent-state-based distribution schemes for two-qubit entanglement, the present scheme relies only upon a simple discrimination of two coherent states with opposite signs, which can be performed in a quantum mechanically optimal fashion via a beam splitter and two on-off detectors. The entanglement purification utilizes a scheme that avoids the usage of ancillary entangled resources. Our repeater scheme exhibits reasonable fidelities and repeater rates providing an attractive platform for long-distance quantum communication.

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“…In practice, however, no system can * xwwang@mail.bnu.edu.cn † lmkuang@hunnu.edu.cn be completely isolated from surroundings [11], and the system will experience decoherence because of the interaction with environment. Multipartite entanglement, which holds much richer quantum correlations than bipartite entanglement, is known to be very fragile to decoherence and to display subtle decay features [12][13][14][15], especially when an entangled multiparticle state is distributed into several distant recipients [4,16]. Then the conventional entanglement localization strategies may achieves no longer the optimization.…”

Section: Introductionmentioning

confidence: 99%

Manipulation of tripartite-to-bipartite entanglement localization under quantum noises and its application to entanglement distribution

Wang¹,

Tang²,

Yuan³

et al. 2014

J. Phys. B: At. Mol. Opt. Phys.

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This paper is to investigate the effects of quantum noises on entanglement localization by taking an example of reducing a three-qubit Greenberger-Horne-Zeilinger (GHZ) state to a two-qubit entangled state. We consider, respectively, two types of quantum decoherence, i.e., amplitude-damping and depolarizing decoherence, and explore the best von Neumann measurements on one of three qubits of the triple GHZ state for making the amount of entanglement of the collapsed bipartite state be as large as possible. The results indicate that different noises have different impacts on entanglement localization, and that the optimal strategy for reducing a three-qubit GHZ state to a two-qubit one via local measurements and classical communications in the amplitude-damping case is different from that in the noise-free case. We also show that the idea of entanglement localization could be utilized to improve the quality of bipartite entanglement distributing through amplitude-damping channels. These findings might shed a new light on entanglement manipulations and transformations.

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Distribution of entanglement in large-scale quantum networks

Cited by 97 publications

References 122 publications

Quantized recurrence time in unital iterated open quantum dynamics

Quantized recurrence time in unital iterated open quantum dynamics

Quantum repeater based on cavity QED evolutions and coherent light

Manipulation of tripartite-to-bipartite entanglement localization under quantum noises and its application to entanglement distribution

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