An Optimal Design for Universal Multiport Interferometers

TL;DR

This paper introduces a new design for universal multiport interferometers that reduces physical size and enhances robustness to optical losses, improving upon the traditional Reck et al. design.

Contribution

A novel interferometer layout that halves the footprint and increases loss tolerance compared to the standard Reck et al. design.

Findings

Reduces interferometer size by 50%

Improves robustness to optical losses

Maintains universal linear transformation capabilities

Abstract

Universal multiport interferometers, which can be programmed to implement any linear transformation between multiple channels, are emerging as a powerful tool for both classical and quantum photonics. These interferometers are typically composed of a regular mesh of beam splitters and phase shifters, allowing for straightforward fabrication using integrated photonic architectures and ready scalability. The current, standard design for universal multiport interferometers is based on work by Reck et al (Phys. Rev. Lett. 73, 58, 1994). We demonstrate a new design for universal multiport interferometers based on an alternative arrangement of beam splitters and phase shifters, which outperforms that by Reck et al. Our design occupies half the physical footprint of the Reck design and is significantly more robust to optical losses.