Cryogenic CMOS for Quantum Control is CMOS integrated circuits operating at millikelvin temperatures enabling on-chip control and readout of quantum devices, reducing wiring and improving scalability — essential for large-scale quantum computing. Cryo-CMOS solves wiring bottleneck. Cryogenic Challenges CMOS designed for room temperature (300K). At low T (<100 mK), behavior changes: leakage current drops, threshold voltage shifts, mobility reduces. Threshold Voltage Temperature Dependence V_T increases with decreasing temperature (approximately 1-2 mV/K in bulk CMOS). Circuit design must account. Subthreshold Leakage exponentially decreases with temperature. At millikelvin, negligible. Beneficial for low-power circuits. Mobility and Channel Length Modulation electron/hole mobility increases at low T (reduced phonon scattering). Beneficial. Channel length modulation affects gain. Device Matching mismatch increases at low T due to random dopant fluctuations becoming significant relative to thermal voltage. Careful design mitigates. 1/f Noise flicker noise increases at low T (reduced number of charge carriers in oxide defects). Noise spectral density S_f ∝ 1/f. Leakage Paths reverse-biased junctions: leakage current decreases but doesn't vanish. Band-to-band tunneling (BTBT) becomes significant at low T with high fields. Parametric Oscillations nonlinear devices (varactors, Josephson junctions) near parametric resonance amplify. Requires careful circuit design. Operational Amplifiers low-temperature opamps: gain decreases (mobility gain reduction), noise increases (1/f). Compensation and design changes needed. Transimpedance Amplifiers convert current to voltage: I→V amp. Critical for quantum dot readout. Transimpedance Z = feedback resistance R_f. Noise: 4kTR_f noise of feedback resistor, input-referred current noise. Low-Noise Amplifiers minimize added noise for sensitive measurements. Cryogenic BJTs have lower noise than MOSFETs at low T. GaAs/InP heterojunctions used. Cryogenic Resistors thin-film resistors (nichrome, tantalum nitride) stable at low T. Wirewound resistors unreliable (superconductivity). Capacitors thin-film capacitors (MIM) stable. Avoid electrolytic (no mobile ions at low T). Interconnects superconducting wires between room-temperature world and low-T (suspended, isolated from substrate to reduce thermal conduction). Filtering and Shielding magnetic shielding (μ-metal, superconducting) reduces external noise. Low-pass filtering removes high-frequency noise. Temperature Gradients cryogenic circuits dissipate heat in very cold environment. Temperature T₀ + ΔT from dissipation. Affects performance. Power Dissipation Budget limited cooling power: ~μW per watt of dissipation at 4K, ~100 pW at 10 mK. Circuits ultra-low power. Clock Signals CMOS clocking system for control. Phase-locked loops (PLLs) work at low T but with modifications. Control Pulses RF pulses control qubits. Pulse generators, mixers, frequency shifters integrated. Readout Circuits amplify quantum signals (fA currents from quantum dots, μV signals). Sensitive amplifiers critical. Cryogenic Test Structures dummy circuits for characterization. Parameter extraction from low-T measurements. System Integration full quantum control stack: classical pre-processing, control pulse generation, on-chip amplification, post-processing. Power Supply Decoupling low-impedance power delivery. High-frequency noise couples to circuits. Multi-stage filtering. Quantum Device Interaction cryo-CMOS control electrodes couple capacitively or resistively to quantum device. Crosstalk between control lines. Multiplexing many qubits require many control lines. Multiplexing reduces wiring. Integrated addressable control. Future Directions direct quantum-CMOS coupling (circuits sensitive to quantum signals), distributed control architecture (control intelligence close to qubits). Cryogenic CMOS is enabling technology for scaled quantum computing bringing classical control on-chip.