Experimental Fock-State Bunching Capability of Non-Ideal Single-Photon States

TL;DR

This paper introduces an experimental method to assess the ability of imperfect single-photon sources to produce higher Fock states through bunching, providing a new benchmark for quantum photonic technologies.

Contribution

It presents a novel operational criterion based on phase-space interference to evaluate Fock-state bunching capability of non-ideal single-photon sources.

Findings

High-purity photons can achieve a Fock-state capability of at least 14.

The approach accounts for residual multi-photon components, vacuum, and photon statistics dispersion.

Demonstrates a new benchmark for assessing single-photon source quality.

Abstract

Advanced quantum technologies, as well as fundamental tests of quantum physics, crucially require the interference of multiple single photons in linear-optics circuits. This interference can result in the bunching of photons into higher Fock states, leading to a complex bosonic behaviour. These challenging tasks timely require to develop collective criteria to benchmark many independent initial resources. Here we determine whether n independent imperfect single photons can ultimately bunch into the Fock state $|n \rangle$. We thereby introduce an experimental Fock-state bunching capability for single-photon sources, which uses phase-space interference for extreme bunching events as a quantifier. In contrast to autocorrelation functions, this operational approach takes into account not only residual multi-photon components but also vacuum admixture and the dispersion of the individual photon statistics. We apply this approach to high-purity single photons generated from an optical parametric oscillator and show that they can lead to a Fock-state capability of at least 14. Our work demonstrates a novel collective benchmark for single-photon sources and their use in subsequent stringent applications.