Design and characterization of integrated components for SiN photonic quantum circuits

TL;DR

This paper presents the design, fabrication, and calibration of silicon nitride photonic components for integrated quantum circuits, demonstrating high-fidelity CNOT gates suitable for scalable quantum computing.

Contribution

It introduces robust, reproducible silicon nitride photonic components and demonstrates a high-fidelity integrated CNOT gate for quantum photonic circuits.

Findings

Ring resonators with low propagation loss

Directional couplers with minimal insertion loss

CNOT gate fidelity of 99.81% after post selection

Abstract

The design, fabrication, and detailed calibration of essential building blocks towards fully integrated linear-optics quantum computation are discussed. Photonic devices are made from silicon nitride rib waveguides, where measurements on ring resonators show small propagation losses. Directional couplers are designed to be insensitive to fabrication variations. Their offset and coupling lengths are measured, as well as the phase difference between the transmitted and reflected light. With careful calibrations, the insertion loss of the directional couplers is found to be small. Finally, an integrated controlled-NOT circuit is characterized by measuring the transmission through different combinations of inputs and outputs. The gate fidelity for the CNOT operation with this circuit is estimated to be 99.81% after post selection. This high fidelity is due to our robust design, good fabrication reproducibility, and extensive characterizations.