  Recent advances in quantum error correction (QEC) codes for fault-tolerant
quantum computing \cite{Terhal2015} and physical realizations of high-fidelity
qubits in a broad range of platforms \cite{Kok2007, Brown2011, Barends2014,
Waldherr2014, Dolde2014, Muhonen2014, Veldhorst2014} give promise for the
construction of a quantum computer based on millions of interacting qubits.
However, the classical-quantum interface remains a nascent field of
exploration. Here, we propose an architecture for a silicon-based quantum
computer processor based entirely on complementary metal-oxide-semiconductor
(CMOS) technology, which is the basis for all modern processor chips. We show
how a transistor-based control circuit together with charge-storage electrodes
can be used to operate a dense and scalable two-dimensional qubit system. The
qubits are defined by the spin states of a single electron confined in a
quantum dot, coupled via exchange interactions, controlled using a microwave
cavity, and measured via gate-based dispersive readout \cite{Colless2013}. This
system, based entirely on available technology and existing components, is
compatible with general surface code quantum error correction
\cite{Terhal2015}, enabling large-scale universal quantum computation.
