A diamond nanophotonic interface with an optically accessible deterministic electronuclear spin register

Abstract

AbstractA contemporary challenge for the scalability of quantum networks is developing quantum nodes with simultaneous high photonic efficiency and long-lived qubits. Here we present a fibre-packaged nanophotonic diamond waveguide hosting a tin-vacancy centre with a spin-1/2117Sn nucleus. The interaction between the electronic and nuclear spins results in a signature 452(7) MHz hyperfine splitting. This exceeds the natural optical linewidth by a factor of 16, enabling direct optical nuclear spin initialization with 98.6(3)% fidelity and single-shot readout with 80.0(1)% fidelity. The waveguide-to-fibre extraction efficiency of our device of 57(6)% enables the practical detection of five-photon events. Combining the photonic performance with the optically initialized nuclear spin, we demonstrate a spin-gated single-photon nonlinearity with 11(1)% contrast in the absence of an external magnetic field. These capabilities position our nanophotonic interface as a versatile quantum node in the pursuit of scalable quantum networks.