Accurate Self-Configuration of Rectangular Multiport Interferometers

TL;DR

This paper introduces a robust self-configuration algorithm for rectangular multiport interferometers that compensates for fabrication errors, enabling scalable photonic quantum and machine-learning hardware.

Contribution

The authors develop a novel configuration method based on $2\times 2$ block decomposition that overcomes geometric limitations of rectangular meshes and improves error robustness.

Findings

Reduces fabrication error effects quadratically in rectangular meshes

Requires no prior process variation knowledge

Enhances scalability of photonic quantum and machine-learning systems

Abstract

Multiport interferometers based on integrated beamsplitter meshes are widely used in photonic technologies. While the rectangular mesh is favored for its compactness and uniformity, its geometry resists conventional self-configuration approaches, which are essential to programming large meshes in the presence of fabrication error. Here, we present a new configuration algorithm, related to the $2\times 2$ block decomposition of a unitary matrix, that overcomes this limitation. Our proposed algorithm is robust to errors, requires no prior knowledge of the process variations, and relies only on external sources and detectors. We show that self-configuration using this technique reduces the effect of fabrication errors by the same quadratic factor observed in triangular meshes. This relaxes a significant limit to the size of multiport interferometers, removing a major roadblock to the scaling of optical quantum and machine-learning hardware.