Cavity-assisted single-shot T center spin readout

High-fidelity spin readout is a crucial component for quantum information processing with optically interfaced solid-state spins. Here, we propose and investigate two theoretical protocols for fast single-shot readout of cavity-coupled single T center electronic spins. For fluorescence-based readout, we selectively couple one of the T center spin-conserving transitions to a single-mode photonic cavity, exploiting the enhancement of the fluorescence emission and cyclicity. For reflection-based readout, we leverage the spin-dependent cavity reflection contrast to generate the qubit readout signal. We show that the cavity reflection approach enables high-fidelity spin readout even when the T center only has a modest cyclicity. With realistic system parameters, such as cavity quality factor $Q = 2\times10^5$ and T center optical linewidth $\Gamma/2\pi = 100$ MHz, we calculate a single-shot readout fidelity exceeding 99% within 8.7 $\mu$s for both spin readout protocols.