Characterization of optical quantum circuits using resonant phase shifts

TL;DR

This paper introduces a method to characterize linear optical quantum circuits by measuring phase shifts caused by integrated resonators, enabling detailed analysis of complex quantum gates.

Contribution

It presents a novel technique using resonant phase shifts to extract detailed parameters of optical quantum circuits, including coupling ratios and phase relations.

Findings

Successfully determined phases in a Mach-Zehnder interferometer.

Applied method to a CNOT gate for quantum computation.

Measured coupling ratios and phases in complex optical circuits.

Abstract

We demonstrate that important information about linear optical circuits can be obtained through the phase shift induced by integrated optical resonators. As a proof of principle, the phase of an unbalanced Mach-Zehnder interferometer is determined. Then the method is applied to a complex optical circuit designed for linear optical quantum computation. In this controlled-NOT gate with qubit initialization and tomography stages, the relative phases are determined as well as the coupling ratios of its directional couplers.