Einstein-Podolsky-Rosen Energy-Time Entanglement of Narrowband Biphotons

TL;DR

This paper demonstrates the direct measurement and verification of energy-time entanglement in narrowband biphotons generated from cold atoms, confirming quantum correlations through joint spectrum and EPR steering criteria.

Contribution

It provides the first direct characterization of energy-time entanglement of narrowband biphotons from cold atoms using advanced measurement techniques.

Findings

Measured two-photon temporal correlations with nanosecond resolution.

Determined joint spectrum using a narrow linewidth optical cavity.

Verified entanglement via violation of separability and EPR steering inequalities.

Abstract

We report the direct characterization of energy-time entanglement of narrowband biphotons produced from spontaneous four-wave mixing in cold atoms. The Stokes and anti-Stokes two-photon temporal correlation is measured by single-photon counters with nano second temporal resolution, and their joint spectrum is determined by using a narrow linewidth optical cavity. The energy-time entanglement is verified by the joint frequency-time uncertainty product of 0.063 +/- 0.0044, which does not only violate the separability criterion but also satisfies the continuous variable Einstein-Podolsky-Rosen steering inequality.