Generation of narrow-band polarization-entangled photon pairs at a rubidium D1 line

TL;DR

This paper reports the generation of narrow-band polarization-entangled photon pairs at 795 nm using cavity-enhanced SPDC, suitable for quantum memory applications, with high Bell inequality violation.

Contribution

It demonstrates a cavity-enhanced SPDC source producing narrow-band entangled photons resonant with rubidium D1 line, matching atomic memory bandwidth.

Findings

Linewidth of 15 MHz matching atomic memory

Bell parameter S=2.73, violating Bell-CHSH inequality

Photon pairs suitable for quantum communication

Abstract

Using the process of cavity-enhanced spontaneous parametric down-conversion (SPDC), we generate a narrow-band polarization-entangled photon pair resonant on the rubidium (Rb) D1 line (795 nm). The degenerate single-mode photon pair is selected by multiple temperature controlled etalons. The linewidth of generated polarization-entangled photon pairs is 15 MHz which matches the typical atomic memory bandwidth. The measured Bell parameter for the polarization-entangled photons S=2.73+-0.04 which violates the Bell-CHSH inequality by ~18 standard deviations. The presented entangled photon pair source could be utilized in quantum communication and quantum computing based on quantum memories in atomic ensemble.