Challenges in Scaling-up the Control Interface of a Quantum Computer

Challenges at the quantum-classical interface are examined with the goal of architecting a scaled-up quantum computer comprising many thousands of qubits. Separating the distinct sub-systems of the interface that perform readout and control, general arguments are given for why distributing the components of these sub-systems over significant distances and across large temperature gradients presents a major challenge to scaling-up the technology. Largely addressing these issues, an architecture for the interface that leverages cryo-CMOS circuits proximal to the quantum plane is motivated, leveraging protocols that enable massively-parallel readout of qubits via frequency multiplexing.