Process verification of two-qubit quantum gates by randomized
benchmarking

A. D. Córcoles, Jay M. Gambetta, Jerry M. Chow, John A. Smolin, Matthew Ware, J. D. Strand, B. L. T. Plourde, M. Steffen

Published:

We implement a complete randomized benchmarking protocol on a system of two
superconducting qubits. The protocol consists of randomizing over gates in the
Clifford group, which experimentally are generated via an improved two-qubit
cross-resonance gate implementation and single-qubit unitaries. From this we
extract an optimal average error per Clifford of 0.0936. We also perform an
interleaved experiment, alternating our optimal two-qubit gate with random
two-qubit Clifford gates, to obtain a two-qubit gate error of 0.0653. We
compare these values with a two-qubit gate error of ~0.12 obtained from quantum
process tomography, which is likely limited by state preparation and
measurement errors.