  Solid-state quantum computers require classical electronics to control and
readout individual qubits and to enable fast classical data processing [1-3].
Integrating both subsystems at deep cryogenic temperatures [4], where
solid-state quantum processors operate best, may solve some major scaling
challenges, such as system size and input/output (I/O) data management [5].
Spin qubits in silicon quantum dots (QDs) could be monolithically integrated
with complementary metal-oxide-semiconductor (CMOS) electronics using
very-large-scale integration (VLSI) and thus leveraging over wide manufacturing
experience in the semiconductor industry [6]. However, experimental
demonstrations of integration using industrial CMOS at mK temperatures are
still in their infancy. Here we present a cryogenic integrated circuit (IC)
fabricated using industrial CMOS technology that hosts three key ingredients of
a silicon-based quantum processor: QD arrays (arranged here in a
non-interacting 3x3 configuration), digital electronics to minimize control
lines using row-column addressing and analog LC resonators for multiplexed
readout, all operating at 50 mK. With the microwave resonators (6-8 GHz range),
we show dispersive readout of the charge state of the QDs and perform combined
time- and frequency-domain multiplexing, enabling scalable readout while
reducing the overall chip footprint. This modular architecture probes the
limits towards the realization of a large-scale silicon quantum computer
integrating quantum and classical electronics using industrial CMOS technology.
