Room-temperature photonic quantum computing in integrated silicon photonics with germanium-silicon single-photon avalanche diodes

Abstract: Most, if not all, photonic quantum computing (PQC) relies upon superconducting nanowire single-photon detectors (SNSPDs) based on niobium (Nb) operated at a temperature < 4 K. This paper proposes and analyzes 300 K waveguide-integrated germanium-silicon (GeSi) single-photon avalanche diodes (SPADs) based on the recently demonstrated normal-incidence GeSi SPADs operated at room temperature, and shows that their performance is competitive against that of SNSPDs in a series of metrics for PQC with a reasonable time-gating window to resolve the issue of dark-count rate (DCR). These GeSi SPADs become photon-number-resolving avalanche diodes (PNRADs) by deploying a spatially-multiplexed M-fold-waveguide array of M GeSi SPADs. Using on-chip waveguided spontaneous four-wave mixing (SFWM) sources and waveguided field-programmable interferometer mesh (FPIM) circuits, together with the high-metric SPADs and PNRADs, high-performance quantum computing at room temperature is predicted for this PQC architecture.