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.