Asymptotically Fault-Tolerant Programmable Photonics

TL;DR

This paper introduces two innovative circuit architectures for programmable photonics that achieve fault tolerance by overcoming errors in Mach-Zehnder interferometers, enabling scalable and large-scale photonic circuits.

Contribution

The paper presents two modified circuit architectures that enable perfect state realization, overcoming error limitations and allowing scalable, large photonic meshes without additional phase shifters.

Findings

Matrix fidelity remains high regardless of mesh size.

Architectures support self-configuration and are more compact.

Eliminates major obstacle to large-scale photonic circuits.

Abstract

Component errors limit the scaling of programmable coherent photonic circuits. These errors arise because the standard tunable photonic coupler -- the Mach-Zehnder interferometer (MZI) -- cannot be perfectly programmed to the cross state. Here, we introduce two modified circuit architectures that overcome this limitation: (1) a 3-splitter MZI mesh for generic errors, and (2) a broadband MZI+Crossing design for correlated errors. Because these designs allow for perfect realization of the cross state, the matrix fidelity no longer decreases with mesh size, allowing scaling to arbitrarily large meshes. The proposed architectures support progressive self-configuration, are more compact than previous MZI-doubling schemes, and do not require additional phase shifters. This eliminates a major obstacle to the development of very-large-scale linear photonic circuits.