Bell Inequalities for Quantum Optical Fields

TL;DR

This paper introduces new Bell inequalities for quantum optical fields that eliminate loopholes present in traditional intensity-based inequalities, enabling more reliable detection of entanglement and consistency with Bell's Theorem.

Contribution

The authors develop alternative Bell inequalities using averaged local rates, overcoming loopholes and improving entanglement detection in quantum optics.

Findings

New inequalities detect entanglement where traditional ones fail.

The inequalities are fully consistent with Bell's Theorem.

They provide better device-independent entanglement detection.

Abstract

We show that the "practical" Bell inequalities, which use intensities as the observed variables, commonly used in quantum optics and widely accepted in the community, suffer from an inherent loophole, which severely limits the range of local hidden variable theories of light, which are invalidated by their violation. We present alternative inequalities which do not suffer from any (theoretical) loophole. The new inequalities use redefined correlation functions, which involve averaged products of local rates rather than intensities. Surprisingly, the new inequalities detect entanglement in situations in which the "practical" ones fail. Thus, we have two for the price on one: full consistency with Bell's Theorem, and better device-independent detection of entanglement.