Design of CMOS RFICs for the Quantum Microprocessor

The year 2025 marks a century since the birth of quantum mechanics and the rise of the second quantum revolution, shifting focus from observing to engineering quantum phenomena for advanced technologies. Quantum computing, leveraging superposition, coherence, and entanglement, requires physical processors using qubits. Solid-state platforms, such as superconducting circuits and semiconductor spin qubits, are promising due to scalability, long coherence times, and CMOS compatibility but require deep-cryogenic operation to minimize thermal noise and decoherence. This drives the need for compact, low-power cryogenic electronics for qubit control and readout. This thesis addresses these challenges through theoretical analysis and the design of integrated cryogenic circuits. The first part establishes the framework of quantum computation, defining quantum gates and fidelity as a link between electronic imperfections and algorithm performance. The core research focuses on cryogenic RFICs, particularly a Single Side Band (SSB) modulator for qubit control implemented in SG13G2 130nm SiGe BiCMOS technology. Unlike most approaches relying on room-temperature designs with post-fabrication tuning, this work uses a cryogenic design kit, reducing ancillary circuits, power, and area. The modulator employs a two-stage mixing architecture to suppress unwanted sidebands and control qubits at specific frequencies. Designed for 4K operation, it generates signals from 100MHz to 6GHz, occupies 1mm², and dissipates 23mW. An optimized version integrates a multiplexed current-mode logic frequency divider, with alternative as injection-locking and true single-phase clock dividers explored for scalable, energy-efficient designs. Further work addresses qubit readout, for which several cryogenic LNAs were designed during a research stay at CEA-Leti (Grenoble, France) using STMicroelectronics BiCMOS55X technology. The LNAs present gains of 12-46dB, 0.42-1.9dB noise figures, 5-29mW power, and bandwidths covering 0.1-2GHz and 4-8GHz, supporting various qubit platforms. Power management was also studied through the characterization of a cryogenic voltage regulator at TU Delft (Netherlands), which should bridge room-temperature and cryogenic stages, providing a clean and stable supply voltage. This Ph.D. thesis bridges the gap between quantum physicists and electronic engineers. It advances cryogenic circuit design through two major contributions: a cryogenic SSB modulator designed using a cryogenic design kit to reduce power and area, and that implements a novel two-stage up-conversion architecture that minimizes parasitic effects and simplifies filtering.