Photon indistinguishability measurements under pulsed and continuous excitation

TL;DR

This paper develops a method to accurately measure photon indistinguishability under continuous wave excitation, aligning it with pulsed excitation results, and verifies it experimentally using single molecules.

Contribution

It introduces a new approach to extract photon indistinguishability from cw measurements, overcoming previous limitations related to detector timing and excitation regimes.

Findings

Derived a correlation function-based method for cw measurements

Experimentally verified equivalence between cw and pulsed excitation results

Applied the method to single-molecule photon sources

Abstract

The indistinguishability of successively generated photons from a single quantum emitter is most commonly measured using two-photon interference at a beam splitter. Whilst for sources excited in the pulsed regime the measured bunching of photons reflects the full wavepacket indistinguishability of the emitted photons, for continuous wave (cw) excitation the inevitable dependence on detector timing resolution and driving strength obscures the underlying photon interference process. Here we derive a method to extract the photon indistinguishability from cw measurements by considering the relevant correlation functions. The equivalence of both methods is experimentally verified through comparison of cw and pulsed excitation of an archetypal source of photons, a single molecule.