Partially Nondestructive Continuous Detection of Individual Traveling Optical Photons

TL;DR

This paper demonstrates a method for partially nondestructive, continuous detection of individual traveling optical photons using a slow-light medium and an optical cavity, revealing strong quantum correlations.

Contribution

It introduces a novel technique for continuous, partially nondestructive measurement of traveling photons with measurable quantum efficiency and correlation properties.

Findings

Achieved strong correlations with g^{(2)}_{sp}=4.4(5).

Observed conditional nondestructive quantum efficiency up to 13%.

Confirmed non-classical correlations via Cauchy-Schwarz inequality violation.

Abstract

We report the continuous and partially nondestructive measurement of optical photons. For a weak light pulse traveling through a slow-light optical medium (signal), the associated atomic-excitation component is detected by another light beam (probe) with the aid of an optical cavity. We observe strong correlations of $g^{(2)}_{sp}=4.4(5)$ between the transmitted signal and probe photons. The observed (intrinsic) conditional nondestructive quantum efficiency ranges between 13% and 1% (65% and 5%) for a signal transmission range of 2% to 35%, at a typical time resolution of 2.5 $\mu$s. The maximal observed (intrinsic) device nondestructive quantum efficiency, defined as the product of the conditional nondestructive quantum efficiency and the signal transmission, is 0.5% (2.4%). The normalized cross-correlation function violates the Cauchy-Schwarz inequality, confirming the non-classical character of the correlations.