Cryo-CMOS Electronics For Quantum Computing: Bringing Classical Electronics Closer To Qubits In Space And Temperature

The core of a quantum computer is a quantum processor, which is composed of quantum bits (qubits). Qubits can be implemented in many flavors, but they are fragile, and their state has a tendency to decay in time. To be usable for computation, qubits must be corrected in real time by a classical controller. The controller must also see that desired computations are executed. Today, the control of qubits is performed at room temperature (RT) by racks of instruments, while the qubits operate at several tens of milli-Kelvin. To ensure compactness and, eventually, scalability, we have proposed and implemented CMOS circuits designed to operate at a few degrees Kelvin. This makes complex thermalization circuits unnecessary, potentially enabling superconductive interconnects, which would enable virtually zero resistance and low thermal conductivity. Cryogenic CMOS, or cryo-CMOS, technology was chosen to achieve classical control due to its scalable nature and overall miniaturization opportunities. Cryo-CMOS circuits and systems need to be carefully designed to ensure strict power budgets, while achieving quite advanced specifications in terms of noise and bandwidth. We review the requirements of a classical controller and cryo-CMOS circuits and systems developed for spin qubits in our lab. Results and perspectives are presented with a discussion about a road map for the future.