Heralded non-destructive quantum entangling gate with single-photon sources

TL;DR

This paper demonstrates a heralded, non-destructive quantum entangling gate using on-demand single-photon sources, achieving high fidelity in a linear optical system, advancing optical quantum computation.

Contribution

First experimental demonstration of a heralded CNOT gate with free-flying photons using a semiconductor quantum dot source.

Findings

Achieved a CNOT gate fidelity of 87.8%.

Generated Bell states with 83.4% fidelity.

Showed feasibility of scalable photon-photon quantum logic gates.

Abstract

Heralded entangling quantum gates are an essential element for the implementation of large-scale optical quantum computation. Yet, the experimental demonstration of genuine heralded entangling gates with free-flying output photons in linear optical system, was hindered by the intrinsically probabilistic source and double-pair emission in parametric down-conversion. Here, by using an on-demand single-photon source based on a semiconductor quantum dot embedded in a micro-pillar cavity, we demonstrate a heralded controlled-NOT (CNOT) operation between two single photons for the first time. To characterize the performance of the CNOT gate, we estimate its average quantum gate fidelity of ($87.8\pm1.2$)%. As an application, we generated event-ready Bell states with a fidelity of ($83.4\pm2.4$)%. Our results are an important step towards the development of photon-photon quantum logic gates.