Entanglement-free certification of entangling gates

TL;DR

This paper presents a method to certify entangling quantum gates without generating entanglement, using quantum discord as a resource, enabling benchmarking in noisy, real-world quantum systems.

Contribution

It introduces a protocol that uses quantum discord to verify entangling gates without entanglement, suitable for noisy and mixed-state quantum architectures.

Findings

Successfully implemented in single-photon regime

Effective under high noise and imperfect gates

Provides a practical benchmarking method

Abstract

Not all quantum protocols require entanglement to outperform their classical alternatives. The nonclassical correlations that lead to this quantum advantage are conjectured to be captured by quantum discord. Here we demonstrate that discord can be explicitly used as a resource: certifying untrusted entangling gates without generating entanglement at any stage. We implement our protocol in the single-photon regime, and show its success in the presence of high levels of noise and imperfect gate operations. Our technique offers a practical method for benchmarking entangling gates in physical architectures in which only highly-mixed states are available.