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Frontiers in Optics

Generation of entangled cats from photon number states

S. U. Shringarpure, J. D. Franson

Published Jan 1, 2020• 0 citations
Publisher

Abstract

A phase-entangled cat state is created when a number state passes through a beamsplitter. This entanglement is used to violate Bell’s inequality using large Kerr media. This approach may have applications in quantum communications.
DOI
10.1364/ls.2020.lm1f.2

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We study Greenberger-Horne-Zeilinger--type (GHZ-type) and WWW-type three-mode entangled coherent states. Both 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 WWW-type entangled coherent states, additional nonlinear interactions are needed. We also propose an optical scheme to generate WWW-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 WWW-type entangled coherent states. Furthermore, it is also robust against inefficiencies of the single-photon source and the photon detectors.