  The most promising quantum algorithms require quantum processors hosting
millions of quantum bits when targeting practical applications. A major
challenge towards large-scale quantum computation is the interconnect
complexity. In current solid-state qubit implementations, a major bottleneck
appears between the quantum chip in a dilution refrigerator and the room
temperature electronics. Advanced lithography supports the fabrication of both
CMOS control electronics and qubits in silicon. When the electronics are
designed to operate at cryogenic temperatures, it can ultimately be integrated
with the qubits on the same die or package, overcoming the wiring bottleneck.
Here we report a cryogenic CMOS control chip operating at 3K, which outputs
tailored microwave bursts to drive silicon quantum bits cooled to 20mK. We
first benchmark the control chip and find electrical performance consistent
with 99.99% fidelity qubit operations, assuming ideal qubits. Next, we use it
to coherently control actual silicon spin qubits and find that the cryogenic
control chip achieves the same fidelity as commercial instruments. Furthermore,
we highlight the extensive capabilities of the control chip by programming a
number of benchmarking protocols as well as the Deutsch-Josza algorithm on a
two-qubit quantum processor. These results open up the path towards a fully
integrated, scalable silicon-based quantum computer.
