A Cryo-CMOS Electron/Nuclear Spin Controller with Combined GHz/MHz Drivers for Color-Center Qubits

Color centers in diamond are a promising quantum-computing platform due to their long coherence times and operation at elevated cryogenic temperatures. This paper presents a 40-nm cryo-CMOS digital-intensive controller that employs a class-D amplifier with a 1-bit $\Delta\Sigma$ quantizer to generate precise, low-noise MHz pulses for nuclear-spin control, and a polar architecture to produce envelope-shaped GHz pulses for electron-spin control. The controller further features merged differential GHz/MHz output drivers, enabling seamless mode switching between electron- and nuclear-spin control. Implemented in 40-nm CMOS and measured at 4\,K, the controller meets the requirements for 99.99\% qubit control fidelity and delivers higher output current with improved efficiency at higher operating frequencies compared to prior art.