Violation of Bell Inequality by Four-Photon Greenberger-Horne-Zeilinger State with a Phase from a Warm Atomic Ensemble

[摘要] A Greenberger-Horne-Zeilinger (GHZ) entangled state with a phase is crucial for realizing desired multipartite quantum states for practical applications. Here, it is reported that the violations of the general Bell inequality (GBI) introduced in using the four-photon polarization-entangled phase-GHZ state realized via intrinsic polarization correlation and collective two-photon coherence in the 5S(1/2)-5P(3/2)-5D(5/2) transition of Rb-87 atoms. The phase-GHZ state can be achieved by the unitary transformation of only one local phase of the four photons. Theoretically, the GHZ state with the & pi;/4 phase affords maximal violation of the GBI of 2 & RADIC;2 at the local measurement settings of the Pauli operators & sigma;(x) and & sigma;(y). Strong violations of the GBI of the phase-GHZ state by 47 standard deviations are experimentally demonstrated. In addition to the entanglement witness for the phase-GHZ state, the results represent a genuine four-photon entanglement of the phase-GHZ state, thereby providing a novel resource for realizing photonic quantum computation, magic-state distillation from entangled states, and quantum networks based on atom-photon interactions.

[效力级别]  Early Access

[关键词] QUANTUM;ENTANGLEMENT;GENERATION