  A key virtue of spin qubits is their sub-micron footprint, enabling a single
silicon chip to host the millions of qubits required to execute useful quantum
algorithms with error correction. With each physical qubit needing multiple
control lines however, a fundamental barrier to scale is the extreme density of
connections that bridge quantum devices to their external control and readout
hardware. A promising solution is to co-locate the control system proximal to
the qubit platform at milli-kelvin temperatures, wired-up via miniaturized
interconnects. Even so, heat and crosstalk from closely integrated control have
potential to degrade qubit performance, particularly for two-qubit entangling
gates based on exchange coupling that are sensitive to electrical noise. Here,
we benchmark silicon MOS-style electron spin qubits controlled via
heterogeneously-integrated cryo-CMOS circuits with a low enough power density
to enable scale-up. Demonstrating that cryo-CMOS can efficiently enable
universal logic operations for spin qubits, we go on to show that mill-kelvin
control has little impact on the performance of single- and two-qubit gates.
Given the complexity of our milli-kelvin CMOS platform, with some 100-thousand
transistors, these results open the prospect of scalable control based on the
tight packaging of spin qubits with a chiplet style control architecture.
