Southwest Quantum Information and Technology

Full reconstruction of all correlated errors in large-scale quantum computers

Presenting Author: Joseph Emerson, University of Waterloo, Quantum Benchmark Inc.
Contributing Author(s): Joel Wallman, Dar Dahlen, Ian Hincks

In this talk I will describe how the cycle benchmarking protocol enables teams to identify all errors and error correlations for any gate-combination of interest. I will provide experimental data from multi-qubit superconducting qubit and ion trap quantum computers, revealing that: (1) in leading platforms, cross-talk and other error correlations can be much more severe than expected, even many order-of-magnitude larger than expected based on independent error models; these cross-talk errors can induce errors on other qubits (e.g., idling qubits) that are an order of magnitude larger than the errors on the qubits in the domain of the gate operation; and thus (3) elementary gate error assessments such as standard and interleaved randomized benchmarking (RB) and gate-set tomography (GST) can give a very misleading picture of the actual "in vivo" errors limiting the performance of a large-scale circuit. I will then discuss how the aggregate error rates measured under cycle benchmarking can be applied to provide a bound on the accuracy of families of circuits implemented via randomized compiling. This will be an important tool for benchmarking algorithms and the `quantum processing power" of hardware performance in what I call the `quantum discovery regime', viz., the regime of large-scale quantum computations that lay beyond the horizon of classical digital computation, where cross-entropy benchmarking and quantum volume can no longer be measured.

(Session 3 : Saturday from 2:45pm - 3:15pm)