Noise-tolerant tomography of multimode linear optical interferometers with single photons

TL;DR

This paper introduces a robust, loss-tolerant method for reconstructing the transfer matrix of multimode linear optical interferometers using photon correlation analysis, validated through experiments on a 4-mode device.

Contribution

The paper presents a novel, loss-tolerant tomography technique that simplifies experimental requirements and improves accuracy in characterizing linear optical networks.

Findings

High fidelity matrix reconstruction demonstrated

Effective in boson sampling experiments

Robust to measurement errors

Abstract

Linear optical networks are fundamental to the advancement of quantum technologies, including quantum computing, communication, and sensing. The accurate characterization of these networks, described by unitary matrices, is crucial to their effective utilization and scalability. In this work, we present the method for reconstructing the transfer matrix of a linear optical interferometer based on the analysis of cross-correlation functions of photon counts between pairs of output modes. Our approach accounts for losses and photon indistinguishability, making it robust to experimental imperfections. By minimizing the requirements for the input states, the method simplifies the experimental implementation. We demonstrate the effectiveness of our technique through theoretical modeling and experimental validation in a 4-mode programmable integrated optical interferometer. The results show high fidelity in matrix reconstruction and successful application in boson sampling experiments. In addition, we provide a comprehensive formalism for correlation functions and discuss the robustness of the method to measurement errors. This work offers a practical and efficient solution for characterizing linear-optical networks, paving the way for scaling up photonic quantum technologies.