On-chip spin-photon entanglement based on single-photon scattering

TL;DR

This paper demonstrates a rapid, on-chip quantum gate entangling a photon with a quantum-dot spin, advancing quantum network components by leveraging sequential photon scattering and heralded detection.

Contribution

It introduces a fast, heralded on-chip entangling gate between a photon and a quantum-dot spin using sequential scattering, immune to spectral wandering.

Findings

Gate operates on sub-microsecond timescale

Heralding ensures high fidelity despite spectral wandering

Achieves on-chip entanglement for quantum networking

Abstract

The realization of on-chip quantum gates between photons and solid-state spins is a key building block for quantum-information processors, enabling, e.g., distributed quantum computing, where remote quantum registers are interconnected by flying photons. Self-assembled quantum dots integrated in nanostructures are one of the most promising systems for such an endeavor thanks to their near-unity photon-emitter coupling and fast spontaneous emission rate. Here we demonstrate an on-chip entangling gate between an incoming photon and a stationary quantum-dot spin qubit. The gate is based on sequential scattering of a time-bin encoded photon with a waveguide-embedded quantum dot and operates on sub-microsecond timescale; two orders of magnitude faster than other platforms. Heralding on detection of a reflected photon renders the gate fidelity fully immune to spectral wandering of the emitter. These results represent a major step in realizing a quantum node capable of both photonic entanglement generation and on-chip quantum logic, as demanded in quantum networks and quantum repeaters.