We study GHZ-type and W-type three-mode entangled coherent states. Both thetypes of entangled coherent states violate Mermin's version of the Bellinequality with threshold photon detection (i.e., without photon counting).Such an experiment can be performed using linear optics elements and thresholddetectors with significant Bell violations for GHZ-type entangled coherentstates. However, to demonstrate Bell-type inequality violations for W-typeentangled coherent states, additional nonlinear interactions are needed. Wealso propose an optical scheme to generate W-type entangled coherent states infree-traveling optical fields. The required resources for the generation are asingle-photon source, a coherent state source, beam splitters, phase shifters,photodetectors, and Kerr nonlinearities. Our scheme does not necessarilyrequire strong Kerr nonlinear interactions, i.e., weak nonlinearities can beused for the generation of the W-type entangled coherent states. Furthermore,it is also robust against inefficiencies of the single-photon source and thephoton detectors.
展开▼
