The SWITCH test for discriminating quantum evolutions

TL;DR

The paper introduces the SWITCH test, a quantum circuit designed to distinguish between two quantum evolution operators, enabling fidelity estimation and applications in quantum communication and experimental implementations.

Contribution

It presents a novel quantum circuit for operator discrimination, extending the SWAP test concept to quantum evolutions with potential practical applications.

Findings

The SWITCH test can effectively discriminate quantum operators.

It allows estimation of fidelity between quantum evolutions.

Potential for implementation in quantum communication and experiments.

Abstract

We propose a quantum circuit to discriminate between two arbitrary quantum evolution operators. It permits to test the equality of two quantum operators and to estimate a fidelity measure of them. The relation of the proposal to the SWAP test for discriminating two quantum states is analyzed. We also discuss potential applications for the discrimination of quantum communication channels and possible laboratory implementations with light along the same lines of recent experimental realizations of quantum superpositions of causal orders exploiting the different degrees of freedom of photons. We also discuss hardware efficient realizations for noisy intermediate scale quantum computers.