Establishing trust in quantum computations

TL;DR

This paper introduces an efficient method to measure the fidelity of quantum computations, enabling trust in results from complex quantum hardware without classical simulation verification.

Contribution

It presents a novel technique using mirror circuits to accurately quantify the execution fidelity of quantum algorithms on large-scale quantum computers.

Findings

Effective fidelity measurement for quantum algorithms

Applicable to near-term and future quantum hardware

Enables trust in quantum computation results

Abstract

Quantum computing hardware has grown sufficiently complex that it often can no longer be simulated by classical computers, but its computational power remains limited by errors. These errors corrupt the results of quantum algorithms, and it is no longer always feasible to use classical simulations to directly check the correctness of quantum computations. Without practical methods for quantifying the accuracy with which a quantum algorithm has been executed, it is difficult to establish trust in the results of a quantum computation. Here we solve this problem, by introducing a simple and efficient technique for measuring the fidelity with which an as-built quantum computer can execute an algorithm. Our technique converts the algorithm's quantum circuits into a set of closely related ``mirror circuits'' whose success rates can be efficiently measured. It enables measuring the fidelity of quantum algorithm executions both in the near-term, with algorithms run on hundreds or thousands of physical qubits, and into the future, with algorithms run on logical qubits protected by quantum error correction.