Robust Decorrelation of Errors in Quantum Gates by Random Gate Synthesis

Coherent errors in quantum operations are ubiquitous. Whether arising from spurious environmental couplings or errors in control fields, such errors can accumulate rapidly and degrade the performance of a quantum circuit significantly more than an average gate fidelity may indicate. Furthermore, coherent errors are considerably more difficult to model than stochastic errors, and understanding their impact on a generic quantum circuit or algorithm can be challenging. In this talk, we discuss using robust optimal control techniques to construct many different implementations of a target gate, each with a different coherent error. As Hastings and Campbell have recently shown, randomly sampling over that ensemble yields an effective quantum channel that well approximates the target, but with dramatically suppressed coherent error. Our results extend those of Hastings and Campbell to include robustness to drifting external control parameters. We have implemented these constructions using a superconducting qubit and will discuss randomized benchmarking results consistent with a marked reduction in coherent error.