Practical experimental certification of computational quantum gates via twirling

TL;DR

This paper presents an efficient method using twirling experiments to experimentally certify the fidelity of quantum gates, enabling practical validation of quantum computations on current devices without exhaustive process tomography.

Contribution

It adapts twirling experiments for estimating the fidelity of quantum gates, providing a practical and resource-efficient certification method for quantum computing implementations.

Findings

Achieved high-fidelity control of nuclear spins with only 1% fidelity degradation.

Demonstrated the method on a 3-qubit code encoding operation.

Validated the approach on current quantum hardware.

Abstract

Due to the technical difficulty of building large quantum computers, it is important to be able to estimate how faithful a given implementation is to an ideal quantum computer. The common approach of completely characterizing the computation process via quantum process tomography requires an exponential amount of resources, and thus is not practical even for relatively small devices. We solve this problem by demonstrating that twirling experiments previously used to characterize the average fidelity of quantum memories efficiently can be easily adapted to estimate the average fidelity of the experimental implementation of important quantum computation processes, such as unitaries in the Clifford group, in a practical and efficient manner with applicability in current quantum devices. Using this procedure, we demonstrate state-of-the-art coherent control of an ensemble of magnetic moments of nuclear spins in a single crystal solid by implementing the encoding operation for a 3 qubit code with only a 1% degradation in average fidelity discounting preparation and measurement errors. We also highlight one of the advances that was instrumental in achieving such high fidelity control.