  High fidelity single-shot readout of qubits is a crucial component for
fault-tolerant quantum computing and scalable quantum networks. In recent
years, the nitrogen-vacancy (NV) center in diamond has risen as a leading
platform for the above applications. The current single-shot readout of the NV
electron spin relies on resonance fluorescence method at cryogenic temperature.
However, the the spin-flip process interrupts the optical cycling transition,
therefore, limits the readout fidelity. Here, we introduce a spin-to-charge
conversion method assisted by near-infrared (NIR) light to suppress the
spin-flip error. This method leverages high spin-selectivity of cryogenic
resonance excitation and high flexibility of photonionization. We achieve an
overall fidelity $>$ 95% for the single-shot readout of an NV center electron
spin in the presence of high strain and fast spin-flip process. With further
improvements, this technique has the potential to achieve spin readout fidelity
exceeding the fault-tolerant threshold, and may also find applications on
integrated optoelectronic devices.
