A nonlocal polarization interferometer for entanglement detection

TL;DR

This paper introduces a nonlocal polarization interferometer capable of detecting entanglement and identifying Bell states by analyzing correlations dependent on the density matrix's anti-diagonal elements, with experimental validation.

Contribution

The paper presents a novel nonlocal interferometer design that detects entanglement and distinguishes Bell states using polarization correlations, advancing quantum measurement techniques.

Findings

Successfully detects entanglement through correlation measurements.

Differentiates Bell states based on unique correlation signatures.

Experimental results confirm theoretical predictions.

Abstract

We report a nonlocal interferometer capable of detecting entanglement and identifying Bell states statistically. This is possible due to the interferometer's unique correlation dependence on the anti-diagonal elements of the density matrix, which have distinct bounds for separable states and unique values for the four Bell states. The interferometer consists of two spatially separated balanced Mach-Zehnder or Sagnac interferometers that share a polarization entangled source. Correlations between these interferometers exhibit non-local interference, while single photon interference is suppressed. This interferometer also allows for a unique version of the CHSH-Bell test where the local reality is the photon polarization. We present the relevant theory and experimental results.