Testing Bell inequalities with photon-subtracted Gaussian states

TL;DR

This paper compares photon-subtracted Gaussian states and superpositions of coherent states for testing Bell inequalities, analyzing how experimental imperfections affect their suitability for demonstrating quantum nonlocality.

Contribution

It provides a detailed analysis of how experimental factors influence the effectiveness of PSGSs in Bell inequality tests, highlighting the conditions needed for successful demonstrations.

Findings

Optimal transmittivity levels identified for Bell tests.

Mixedness of Gaussian states impacts Bell inequality violation.

Limitations of photon detectors affect experimental feasibility.

Abstract

Recently, photon subtracted Gaussian states (PSGSs) were generated by several experimental groups. Those states were called "Schr\"odinger kittens" due to their similarities to superpositions of coherent states (SCSs) with small amplitudes. We compare the ideal SCSs and the PSGSs for experimental tests of certain types of Bell inequalities. In particular, we analyze the effects of the key experimental components used to generate PSGSs: mixedness of the Gaussian states, limited transmittivity of the beam splitter and the avalanche photodetector which cannot resolve photon numbers. As a result of this analysis, the degrees of mixedness and the beam splitter transmittivity that can be allowed for successful tests of Bell inequalities are revealed.