Comparison of coherence area measurement techniques for bright entangled twin beams

TL;DR

This paper compares two techniques for measuring the coherence area of bright entangled twin beams, demonstrating that a simpler noise analysis method yields results consistent with a more direct spatial correlation measurement.

Contribution

The study provides a comparative analysis of direct and indirect coherence area measurement techniques for bright entangled twin beams, highlighting the effectiveness of a less complex noise analysis approach.

Findings

The indirect noise analysis method produces coherence area estimates consistent with direct correlation measurements.

The indirect technique requires significantly less complex experimental setup.

Both methods are effective for characterizing the coherence properties of bright entangled twin beams.

Abstract

Quantum states of light with multiple spatial modes are fundamental for quantum imaging and parallel quantum information processing. Thus, their characterization, which can be achieved through measurements of the coherence area, is an important area of research. We present a comparative study between two different measurement techniques for the coherence area of bright entangled twin beams of light generated with a four-wave mixing process in a hot rubidium vapor cell. The first one provides a direct characterization of the size of the coherence area and is based on correlation measurements between spatial intensity fluctuations of the twin beams with an electron-multiplying charge-coupled-device camera. The second one provides an indirect measure and is based on a noise analysis of different spatial regions of the twin beams in the time domain with a single photodiode. We show that the indirect technique, which can be implemented with a significantly less complicated measurement scheme, gives an estimate of the size of the coherence area consistent with the direct measurement technique performed in the spatial domain.