# Efficient verification of bosonic quantum channels via benchmarking

## TL;DR

This paper develops practical verification methods for bosonic quantum channels, using average-fidelity witnesses and local measurements, enabling efficient benchmarking of continuous-variable quantum devices.

## Contribution

It introduces experimentally feasible verification schemes for bosonic channels with polynomial sample complexity, including new average-fidelity witnesses for Gaussian channels.

## Key findings

- Verification schemes are feasible with polynomial sample complexity.
- Benchmarking can be performed using only two-mode squeezed vacuum states and local homodyne detection.
- The methods enable reliable testing of quantum components in continuous-variable quantum information.

## Abstract

We aim to devise feasible, efficient verification schemes for bosonic channels. To this end, we construct an average-fidelity witness that yields a tight lower bound for average fidelity plus a general framework for verifying optimal quantum channels. For both multi-mode unitary Gaussian channels and single-mode amplification channels, we present experimentally feasible average-fidelity witnesses and reliable verification schemes, for which sample complexity scales polynomially with respect to all channel specification parameters. Our verification scheme provides an approach to benchmark the performance of bosonic channels on a set of Gaussian-distributed coherent states by employing only two-mode squeezed vacuum states and local homodyne detections. Our results demonstrate how to perform feasible tests of quantum components designed for continuous-variable quantum information processing.