A Cryo-CMOS Homodyne-Demodulation Qubit Readout IC With Continuous-Time Analog Integration for SNR Improvement

This letter presents a homodyne-demodulation readout IC with continuous-time direct analog integration for superconducting qubits. By integration at the analog front end, the effective signal-to-noise ratio is efficiently increased, eliminating the need for a high-performance analog-to-digital converter and costly baseband processing for data recovery. The proposed IC, fabricated in 40-nm CMOS, is verified at 4 K in a dilution refrigerator. The readout fidelity, estimated under real-world conditions, is reported to be 99% within 300 ns.