83 research outputs found

    Quantum Nonlocality for a Mixed Entangled Coherent State

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    Quantum nonlocality is tested for an entangled coherent state, interacting with a dissipative environment. A pure entangled coherent state violates Bell's inequality regardless of its coherent amplitude. The higher the initial nonlocality, the more rapidly quantum nonlocality is lost. The entangled coherent state can also be investigated in the framework of 2Ă—22\times2 Hilbert space. The quantum nonlocality persists longer in 2Ă—22\times2 Hilbert space. When it decoheres it is found that the entangled coherent state fails the nonlocality test, which contrasts with the fact that the decohered entangled state is always entangled.Comment: 20 pages, 7 figures. To be published in J. Mod. Op

    Violation of Bell's inequality using classical measurements and non-linear local operations

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    We find that Bell's inequality can be significantly violated (up to Tsirelson's bound) with two-mode entangled coherent states using only homodyne measurements. This requires Kerr nonlinear interactions for local operations on the entangled coherent states. Our example is a demonstration of Bell-inequality violations using classical measurements. We conclude that entangled coherent states with coherent amplitudes as small as 0.842 are sufficient to produce such violations.Comment: 6 pages, 5 figures, to be published in Phys. Rev.

    GHZ-type and W-type entangled coherent states: generation and Bell-type inequality tests without photon counting

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    We study GHZ-type and W-type three-mode entangled coherent states. Both the types of entangled coherent states violate Mermin's version of the Bell inequality with threshold photon detection (i.e., without photon counting). Such an experiment can be performed using linear optics elements and threshold detectors with significant Bell violations for GHZ-type entangled coherent states. However, to demonstrate Bell-type inequality violations for W-type entangled coherent states, additional nonlinear interactions are needed. We also propose an optical scheme to generate W-type entangled coherent states in free-traveling optical fields. The required resources for the generation are a single-photon source, a coherent state source, beam splitters, phase shifters, photodetectors, and Kerr nonlinearities. Our scheme does not necessarily require strong Kerr nonlinear interactions, i.e., weak nonlinearities can be used for the generation of the W-type entangled coherent states. Furthermore, it is also robust against inefficiencies of the single-photon source and the photon detectors.Comment: 8 pages, 5 figures, to be published in Phys. Rev.

    Quantum entanglement and Bell violation of two coupled cavity fields in dissipative environment

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    We study the quantum entanglement between two coupled cavities, in which one is initially prepared in a mesoscopic superposition state and the other is in the vacuum in dissipative environment and show how the entanglement between two cavities can arise in the dissipative environment. The dynamic behavior of the nonlocality for the system is also investigated.Comment: 12 pages, 5 figure

    Dynamics of Nonlocality for A Two-Mode Squeezed State in Thermal Environment

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    We investigate the time evolution of nonlocality for a two-mode squeezed state in the thermal environment. The initial two-mode pure squeezed state is nonlocal with a stronger nonlocality for a larger degree of squeezing. It is found that the larger the degree of initial squeezing is, the more rapidly the squeezed state loses its nonlocality. We explain this by the rapid destruction of quantum coherence for the strongly squeezed state.Comment: 5 pages, 3 figures, accepted to PR
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