Experimental Demonstration of Unconditional Entanglement Swapping for Continuous Variables

Jia, Xiaojun; Su, Xiaolong; Qing, Pan; Gao, Jiangrui; Xie, Changde; Peng, Kunchi

doi:10.1103/physrevlett.93.250503

Cited by 229 publications

(157 citation statements)

References 15 publications

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“…So far several experiments for CVs have been demonstrated for a coherent state input using quadrature-phase amplitudes of an electromagnetic field mode [6,7,8,9]. Teleportation of quantum entanglement, i.e., entanglement swapping has been also realized [9,10]. Furthermore, CV teleportation has been extended to a multipartite protocol known as a quantum teleportation network [11,12].…”

Section: Introductionmentioning

confidence: 99%

Experimental demonstration of quantum teleportation of a squeezed state

et al. 2005

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Quantum teleportation of a squeezed state is demonstrated experimentally. Due to some inevitable losses in experiments, a squeezed vacuum necessarily becomes a mixed state which is no longer a minimum uncertainty state. We establish an operational method of evaluation for quantum teleportation of such a state using fidelity, and discuss the classical limit for the state. The measured fidelity for the input state is 0.85± 0.05 which is higher than the classical case of 0.73±0.04. We also verify that the teleportation process operates properly for the nonclassical state input and its squeezed variance is certainly transferred through the process. We observe the smaller variance of the teleported squeezed state than that for the vacuum state input.

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Section: Introductionmentioning

confidence: 99%

Experimental demonstration of quantum teleportation of a squeezed state

et al. 2005

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“…The reported entanglement distillation, purification and Gaussification protocol can be iterated 7,8 and combined with already experimentally demonstrated single-photon subtraction [24][25][26] , quantum memory 3 and entanglement swapping 13,14 to build a continuous-variable quantum repeater. Our experiment is thus an important enabling step towards truly long-distance quantum communication with continuous variables.…”

mentioning

confidence: 99%

“…In the regime of continuous variables, entangled states of light can be deterministically generated in optical parametric amplifiers (OPAs), precisely manipulated with linear optics and measured with very high efficiency in balanced homodyne detectors. These entangled two-mode squeezed states show Gaussian probability distributions and were used for quantum teleportation 12 and entanglement swapping 13,14 . Entangled states of the collective spins of two atomic ensembles analogous to two-mode squeezed states have been generated 15 , storage of quantum states of light in an atomic memory has been demonstrated 3 and teleportation from light onto an atomic ensemble has been reported 16 .…”

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confidence: 99%

Preparation of distilled and purified continuous-variable entangled states

et al. 2008

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The distribution of entangled states of light over long distances is a major challenge in the field of quantum information. Optical losses, phase diffusion and mixing with thermal states lead to decoherence and destroy the non-classical states after some finite transmission-line length. Quantum repeater protocols 1,2 , which combine quantum memory 3 , entanglement distillation 4,5 and entanglement swapping 6 , were proposed to overcome this problem. Here we report on the experimental demonstration of entanglement distillation in the continuous-variable regime 7-9 . Entangled states were first disturbed by random phase fluctuations and then distilled and purified using interference on beam splitters and homodyne detection. Measurements of covariance matrices clearly indicate a regained strength of entanglement and purity of the distilled states. In contrast to previous demonstrations of entanglement distillation in the complementary discrete-variable regime 10,11 , our scheme achieved the actual preparation of the distilled states, which might therefore be used to improve the quality of downstream applications such as quantum teleportation 12 .Quantum information makes use of the special properties of quantum states to improve the quality of communication and information processing tasks. Generally, a quantized field can be described by the number operator or alternatively by two non-commuting position and momentum-like operators. The corresponding measurement results have either discrete or continuous spectra and form the basis of discrete-variable or continuous-variable quantum information, respectively. In the regime of continuous variables, entangled states of light can be deterministically generated in optical parametric amplifiers (OPAs), precisely manipulated with linear optics and measured with very high efficiency in balanced homodyne detectors. These entangled two-mode squeezed states show Gaussian probability distributions and were used for quantum teleportation 12 and entanglement swapping 13,14 . Entangled states of the collective spins of two atomic ensembles analogous to two-mode squeezed states have been generated 15 , storage of quantum states of light in an atomic memory has been demonstrated 3 and teleportation from light onto an atomic ensemble has been reported 16 . High-speed quantum cryptography with coherent light beams and homodyne detection has been demonstrated 17 . All these spectacular achievements reveal the great potential of this approach to quantum information processing.A missing piece in this toolbox has been a feasible protocol for entanglement distillation and purification. Entanglement distillation 4,5 extracts from several shared copies of weakly entangled mixed states a single copy of a highly entangled state using only local quantum operations and classical communication between the two parties sharing the states. This turned out to be a very challenging task for continuous-variable states, because it was proved that it is impossible to distil Gaussian entangled states by ...

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“…Photon-number correlated states, for example Einstein-Podolsky-Rosen (EPR) entangled states [7], are an important resource for quantum teleportation [8][9][10][11][12], entanglement swapping [13][14][15], quantum key distribution [16,17], and Bell tests [18,19]. In practice, however, the applicability of these states is hampered by noise effects such as photon losses.…”

Section: Introductionmentioning

confidence: 99%

Quantum state engineering, purification, and number-resolved photon detection with high-finesse optical cavities

et al. 2010

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We propose and analyze a multi-functional setup consisting of high finesse optical cavities, beam splitters, and phase shifters. The basic scheme projects arbitrary photonic two-mode input states onto the subspace spanned by the product of Fock states |n |n with n = 0, 1, 2, . . .. This protocol does not only provide the possibility to conditionally generate highly entangled photon number states as resource for quantum information protocols but also allows one to test and hence purify this type of quantum states in a communication scenario, which is of great practical importance. The scheme is especially attractive as a generalization to many modes allows for distribution and purification of entanglement in networks. In an alternative working mode, the setup allows of quantum non demolition number resolved photodetection in the optical domain.

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Experimental Demonstration of Unconditional Entanglement Swapping for Continuous Variables

Cited by 229 publications

References 15 publications

Experimental demonstration of quantum teleportation of a squeezed state

Experimental demonstration of quantum teleportation of a squeezed state

Preparation of distilled and purified continuous-variable entangled states

Quantum state engineering, purification, and number-resolved photon detection with high-finesse optical cavities

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