Interference of dissimilar photon sources

TL;DR

This paper demonstrates two-photon interference between dissimilar, unsynchronized photon sources with vastly different coherence times, expanding the understanding of quantum interference phenomena.

Contribution

It introduces a technique to observe interference between dissimilar, unsynchronized photon sources with different coherence times and develops a theory explaining the interference visibility.

Findings

Interference observed between laser-stimulated and quantum dot photons.

Visibility limited mainly by detector timing resolution.

Successful interference despite differing photon statistics and coherence times.

Abstract

If identical photons meet at a semi-transparent mirror they appear to leave in the same direction, an effect called "two-photon interference". It has been known for some time that this effect should occur for photons generated by dissimilar sources with no common history, provided the easurement cannot distinguish between the photons. Here we report a technique to observe such interference with isolated, unsynchronized sources whose coherence times differ by several orders of magnitude. In an experiment we interfere photons generated via different physical processes, with different photon statistics. One source is stimulated emission from a tuneable laser, which has Poissonian statistics and a nano-eV bandwidth. The other is spontaneous emission from a quantum dot in a p-i-n diode with a micro-eV linewidth. We develop a theory to explain the visibility of interference, which is primarily limited by the timing resolution of our detectors.