Direct sampling of optical coherence using quantum interference

TL;DR

This paper introduces a quantum interference-based detector that directly measures the mutual coherence of two optical fields, surpassing traditional methods in sensitivity, especially for weak coherence signals.

Contribution

The authors present a novel quantum interference technique using atomic Raman transitions to directly measure optical coherence, reducing photon noise influence.

Findings

Enhanced sensitivity over conventional interferometry for weak coherence signals

Successful implementation of feedback control to balance field interactions

Potential for improved optical coherence measurements in quantum optics

Abstract

We describe a detector that measures the mutual coherence of two optical fields directly using quantum interference, free from photon noise of the individual irradiances. Our approach utilizes Raman transition in an atomic system where the state evolution is driven by the mutual coherence of the fields interacting with the atoms. Feedback control is used to balance the interaction of the fields being characterized, providing a measure of the mutual coherence. We show that the sensitivity of the coherence measurement can be enhanced significantly above that of conventional interferometric methods when the mutual coherence of the two fields is weak.