Iterative configuration of programmable unitary converter based on few layer redundant multi-plane light conversion

TL;DR

This paper introduces a fast, iterative method for configuring multi-plane light conversion devices, significantly improving accuracy and speed, and enhancing robustness against fabrication errors in programmable photonic unitary converters.

Contribution

It develops a novel iterative configuration algorithm for MPLC devices, incorporating a new norm and redundancy layers to improve convergence and robustness.

Findings

Significantly improved convergence with added redundant layers.

Achieved orders of magnitude better accuracy.

Realized a 20-fold speed-up over previous methods.

Abstract

Programmable unitary photonic devices are emerging as promising tools to implement unitary transformation for quantum information processing, machine learning, and optical communication. These devices typically use a rectangular mesh of Mach-Zehnder interferometers (MZIs), which has a clear mathematical structure and can be configured deterministically. However, this mesh architecture is sensitive to fabrication errors, and the correction techniques are still under investigation. In contrast, the multi-plane light conversion (MPLC) architecture is more robust against fabrication errors, but a deterministic method for configuring the converter has not yet been developed due to its complex mathematical structure. In this work, we propose a fast iterative configuration method for MPLC, following the mathematical review of the matrix distance and proposal of a new norm. We show through numerical simulations that adding a few redundant layers significantly improves the convergence of the MPLC architecture, making it a practical and attractive option. We also consider the effects of finite resolution and crosstalk in phase shifters in our simulations. In addition, we propose a phase-insensitive distance suited for applications using only intensity detections. Our method demonstrates orders of magnitude better accuracy and a 20-fold speed-up compared to previous approaches.