Macroscopic Hong-Ou-Mandel interference

TL;DR

This paper demonstrates a macroscopic Hong-Ou-Mandel interference experiment with high photon numbers, revealing high-visibility interference by measuring photon-number difference variance, and provides insights into the temporal mode structure of the quantum states.

Contribution

It introduces a novel measurement technique for high-photon-number states, achieving high-visibility interference and analyzing mode structure, advancing quantum optics experiments.

Findings

Achieved 99.99% visibility in HOM interference with large photon numbers.

Used variance measurement instead of coincidence counting for better results.

Inferred temporal mode structure and entanglement from the interference peak shape.

Abstract

We report on a Hong-Ou-Mandel (HOM) interference experiment for quantum states with photon numbers per mode as large as 10^6 generated via high-gain parametric down conversion (PDC). The standard technique of coincidence counting leads in this case to a dip with a very low visibility. By measuring, instead of coincidence rate, the variance of the photon-number difference, we observe a peak with 99.99% visibility. From the shape of the peak, one can infer information about the temporal mode structure of the PDC radiation, including the degree of frequency/time entanglement.