  Qubit control electronics composed of CMOS circuits are of critical interest
for next generation quantum computing systems. A CMOS-based application
specific integrated circuit (ASIC) fabricated in 14nm FinFET technology was
used to generate and sequence qubit control waveforms and demonstrate a
two-qubit cross resonance gate between fixed frequency transmons. The
controller was thermally anchored to the T = 4K stage of a dilution
refrigerator and the measured power was 23 mW per qubit under active control.
The chip generated single--side banded output frequencies between 4.5 and 5.5
GHz with a maximum power output of -18 dBm. Randomized benchmarking (RB)
experiments revealed an average number of 1.71 instructions per Clifford (IPC)
for single-qubit gates, and 17.51 IPC for two-qubit gates. A single-qubit error
per gate of $\epsilon_{\text{1Q}}$=8e-4 and two-qubit error per gate of
$\epsilon_\text{2Q}$=1.4e-2 is shown. A drive-induced Z-rotation is observed by
way of a rotary echo experiment; this observation is consistent with expected
qubit behavior given measured excess local oscillator (LO) leakage from the
CMOS chip. The effect of spurious drive induced Z-errors is numerically
evaluated with a two-qubit model Hamiltonian, and shown to be in good agreement
with measured RB data. The modeling results suggest the Z-error varies linearly
with pulse amplitude.
