Efficient verification of quantum processes

TL;DR

This paper introduces efficient protocols for verifying quantum processes that significantly reduce resource requirements compared to traditional methods, making process verification more practical for current experiments.

Contribution

It proposes the concept of quantum process verification and develops protocols with exponential and quadratic improvements over existing methods.

Findings

Protocols require only local measurements.

Effective for verifying quantum gates and circuits.

Applicable to quantum measurement verification.

Abstract

Quantum processes, such as quantum circuits, quantum memories, and quantum channels, are essential ingredients in almost all quantum information processing tasks. However, the characterization of these processes remains a daunting task due to the exponentially increasing amount of resources required by traditional methods. Here, by first proposing the concept of quantum process verification, we establish two efficient and practical protocols for verifying quantum processes which can provide an exponential improvement over the standard quantum process tomography and a quadratic improvement over the method of direct fidelity estimation. The efficacy of our protocols is illustrated with the verification of various quantum gates as well as the processes of well-known quantum circuits. Moreover, our protocols are readily applicable with current experimental techniques since only local measurements are required. In addition, we show that our protocols for verifying quantum processes can be easily adapted to verify quantum measurements.