A method for characterizing coherent-state quantum gates

TL;DR

This paper presents an experimental method for characterizing quantum gates acting on superpositions of coherent states, overcoming limitations of standard techniques by using a physics-informed approach and virtual processing of entangled states.

Contribution

It introduces a novel characterization method tailored for non-orthogonal coherent state qubits, bypassing the need for process tomography.

Findings

Successfully implemented the method experimentally

Provided a new parameter to assess gate quality

Demonstrated advantages over standard techniques

Abstract

We discuss and implement experimentally a method for characterizing quantum gates operating on superpositions of coherent states. The peculiarity of this encoding of qubits is to work with a non-orthogonal basis, and therefore some technical limitations prevent us from using standard methods, such as process tomography. We adopt a different technique, that relies on some a-priori knowledge about the physics underlying the functioning of the device. A parameter characterizing the global quality of the quantum gate is obtained by \virtually" processing an entangled state.