Optimal design of error-tolerant reprogrammable multiport interferometers

TL;DR

This paper introduces a novel reprogrammable multiport interferometer design that uses a static beam-splitter and phase shifts, offering improved error tolerance and reduced non-implementable transfer matrices compared to traditional mesh-based approaches.

Contribution

The proposed design replaces error-sensitive Mach-Zehnder meshes with a static beam-splitter and phase shift, enhancing robustness without additional components.

Findings

Design exhibits superior resilience to manufacturing errors and losses.

Power transmissivities can vary from approximately 1/2 to 4/5.

Fraction of non-implementable transfer matrices decreases rapidly with size.

Abstract

Photonic information processing demands programmable multiport interferometers capable of implementing arbitrary transfer matrices, for which planar meshes of error-sensitive Mach-Zehnder interferometers are usually exploited. We propose an alternative design that uses a single static beam-splitter and a variable phase shift as the building block. The design possesses superior resilience to manufacturing errors and losses without extra elements added into the scheme. Namely, the power transmissivities of the static BSs can take arbitrary values in the range from $\approx{}1/2$ to $\approx{}4/5$. We show that the fraction of transfer matrices non-implementable by the interferometers of our design diminishes rapidly with their size.