Quantum interferences and gates with emitter-based coherent photon sources

TL;DR

This paper explores how photon-number coherence in emitter-based sources affects quantum interference, entanglement, and quantum protocol performance, revealing potential errors and modifications in quantum information experiments.

Contribution

It demonstrates the significant impact of photon-number coherence on quantum interference, entanglement, and protocol fidelity, highlighting the need to account for coherence in quantum photonic applications.

Findings

Photon-number coherence alters Hong-Ou-Mandel interference patterns.

It causes errors in indistinguishability measurements.

It modifies heralding efficiency and fidelity in two-qubit gates.

Abstract

Quantum emitters such as quantum dots, defects in diamond or in silicon have emerged as efficient single photon sources that are progressively exploited in quantum technologies. In 2019, it was shown that the emitted single photon states often include coherence with the vacuum component. Here we investigate how such photon-number coherence alters quantum interference experiments that are routinely implemented both for characterising or exploiting the generated photons. We show that it strongly modifies intensity correlation measurements in a Hong-Ou-Mandel experiment and leads to errors in indistinguishability estimations. It also results in additional entanglement when performing partial measurements. We illustrate the impact on quantum protocols by evidencing modifications in heralding efficiency and fidelity of two-qubit gates.