Single-photon detection is a critical step in both quantum computing and quantum information technology. For instance, the measurement of qubit states and the establishment of entanglement in nitrogen vacancy (NV) center quantum computing requires the detection of single photons. Superconducting nanowire single-photon detectors (SNSPDs) are very competitive devices due to their performance in high detection efficiency, high count rates, low dark count rates, and low jitter. However, the readout electronics are usually implemented at room temperature by connecting the dilution refrigerator through coaxial cables, while SNSPD need to work in a cryogenic environment that is close to the qubits. In order to have better integration and reduce the complexity of the wiring when the number of qubits increases, it is essential to position the electronics close to, or even integrated with, the SNSPD and qubits.
In this thesis, a cryogenic CMOS readout for SNSPD is designed and taped-out using TSMC 40 nm technology. The SNSPD is designed for color-center quantum computing, which is anticipated to work in the wavelength range of 619-620 nm and 625-750 nm, and at a temperature of 1.8 K. The readout electronics are expected to operate at 4 K. The system is required to have a detection efficiency of more than 90 % and a dark count rate of less than 1 Hz. With the help of SPICE dynamic model, the SNSPD is reproduced in Cadence Spectre for circuit design. Active quenching is implemented in the readout architecture, allowing for an increased readout resistor, which improves the output slew rate and count rates without any latching while still keeping a high bias current for a higher detection efficiency. Under a -40 degree Celsius simulation, the readout system achieved count rates greater than 20 MHz, an average jitter of 25 ps rms, and a power consumption of 36 uW, while simultaneously expecting to significantly suppress the dark count rates and after pulses.