Effects of squeezing on quantum nonlocality of superpositions of coherent states

TL;DR

This paper investigates how squeezing operations affect Bell-inequality violations in superpositions and entangled coherent states, showing that proper squeezing can enhance quantum nonlocality under certain measurement conditions.

Contribution

It demonstrates that external squeezing can increase Bell violations in superpositions of coherent states, with effects depending on measurement type and squeezing parameters.

Findings

Squeezing can always increase Bell violations with photon parity measurements.

Enhancement of Bell violations with on/off measurements occurs only for moderate amplitudes and squeezing.

Significant improvements are needed in current squeezed states to observe Bell violations experimentally.

Abstract

We analyze effects of squeezing upon superpositions of coherent states (SCSs) and entangled coherent states (ECSs) for Bell-inequality tests. We find that external squeezing can always increase the degrees of Bell violations, if the squeezing direction is properly chosen, for the case of photon parity measurements. On the other hand, when photon on/off measurements are used, the squeezing operation can enhance the degree of Bell violations only for moderate values of amplitudes and squeezing. We point out that a significant improvement is required over currently available squeezed SCSs in order to directly demonstrate a Bell-inequality violation in a real experiment.