Randomized Benchmarking of Multiqubit Gates
John Gaebler, Adam M. Meier, Ting Rei Tan, R. Bowler, Yiheng Lin, David Hanneke, John D. Jost, Jonathan Home, Emanuel H. Knill, Dietrich G. Leibfried, D. J. Wineland · Physical Review Letters · 2012
We describe an extension of single-qubit gate randomized benchmarking that measures the error of multiqubit gates in a quantum information processor. This platform-independent protocol evaluates the performance of Clifford unitaries, which form a basis of fault-tolerant quantum computing. We implemented the benchmarking protocol with trapped ions and found an error per random two-qubit Clifford unitary of 0.162±0.008, thus setting the first benchmark for such unitaries. By implementing a second set of sequences with an extra two-qubit phase gate inserted after each step, we extracted an error per phase gate of 0.069±0.017. We conducted these experiments with transported, sympathetically cooled ions in a multizone Paul trap-a system that can in principle be scaled to larger numbers of ions.