Abstract

Unreliable quantum processes stemming from noisy operations and interactions with the environment represent one of the greatest challenges to be overcome in the development of scalable, fault-tolerant universal quantum computers. Generic characterizations of such quantum processes, however, can be very resource-intensive, and many tools have been developed for identifying particular aspects of a quantum computer. In this article, we verify whether a tool called Swap Test can be used in order to identify decoherence in an implementation-agnostic way. Simulations and experimental results show that a modified version of a Toffoli Swap Test can be employed as an alternative to a full quantum process tomography, consuming considerably less computational resources as a consequence. Moreover, it is also shown to be able to simulate in a generic quantum computer a quantum optical communication link that employs two-photon interference.