Fully On-Chip Single-Photon Hanbury-Brown and Twiss Experiment on a Monolithic Semiconductor-Superconductor Platform.

Fully integrated quantum photonic circuits show a clear advantage in terms of stability and scalability compared to tabletop implementations. They will constitute a fundamental breakthrough in integrated quantum technologies, as a matter of example, in quantum simulation and quantum computation. Despite the fact that only a few building blocks are strictly necessary, their simultaneous realization is highly challenging. This is especially true for the simultaneous implementation of all three key components on the same chip: single-photon sources, photonic logic, and single-photon detectors. Here, we present a fully integrated Hanbury-Brown and Twiss setup on a micrometer-sized footprint consisting of a GaAs waveguide embedding quantum dots as single-photon sources, a waveguide beamsplitter, and two superconducting nanowire single-photon detectors. This enables a second-order correlation measurement on the single-photon level under both continuous-wave and pulsed resonant excitation. The presented proof-of-principle experiment proves the simultaneous realization and operation of all three key building blocks and therefore a major step towards fully integrated quantum optical chips.

Generation, guiding and splitting of triggered single photons from a resonantly excited quantum dot in a photonic circuit.

We demonstrate resonance fluorescence from single In-GaAs/GaAs quantum dots embedded in a rib waveguide beamsplitter structure operated under pulsed laser excitation. A systematic study on the excitation laser pulse duration depicts that a sufficiently small laser linewidth enables a substantial improved single-photon-to-laser-background ratio inside a waveguide chip. This manifests in the observation of clear Rabi oscillations over two periods of the quantum dot emission as a function of laser excitation power. A photon cross-correlation measurement between the two output arms of an on-chip beamsplitter results in a g(2)(0)=0.18, demonstrating the generation, guiding and splitting of triggered single photons under resonant excitation in an on-chip device. The present results open new perspectives for the implementation of photonic quantum circuits with integrated quantum dots as resonantly-pumped deterministic single-photon sources.