Global calibration of large-scale photonic integrated circuits

TL;DR

This paper introduces a global calibration method for large-scale photonic integrated circuits that simultaneously calibrates all active components, improving accuracy and enabling complex quantum photonic experiments.

Contribution

A novel global calibration approach that learns nonlinear phase-current relations for all thermo-optic shifters simultaneously, addressing limitations of traditional methods.

Findings

Successfully calibrated a 12-depth quantum walk PIC

Demonstrated programmable discrete-time quantum walk

Enhanced calibration accuracy for large-scale PICs

Abstract

The growing maturity of photonic integrated circuit (PIC) fabrication technology enables the high integration of an increasing number of optical components onto a single chip. With the incremental circuit complexity, the calibration of active phase shifters in a large-scale PIC becomes a crucially important issue. The traditional one-by-one calibration techniques encounter significant hurdles with the propagation of calibration errors, and achieving the decoupling of all phase shifters for independent calibration is not straightforward. To address this issue, we propose a global calibration approach for large-scale PIC. Our method utilizes a custom network to simultaneously learn the nonlinear phase-current relations for all thermo-optic phase shifters on the PIC by minimizing the negative likelihood of the measurement datasets. Moreover, the reflectivities of all static beam splitter components can also be synchronizedly extracted using this calibration method. As an example, a quantum walk PIC with a circuit depth of 12 is calibrated, and a programmable discrete-time quantum walk is experimentally demonstrated. These results will greatly benefit the applications of large-scale PICs in photonic quantum information processing.