Using Cryogenic CMOS Control Electronics To Enable A Two–Qubit Cross–Resonance Gate

Abstract

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 є1Q=8e-4 and two–qubit error per gate of є2Q=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.