A Hybrid Integrated Quantum Key Distribution Transceiver Chip

TL;DR

This paper presents a hybrid integrated quantum key distribution transceiver chip combining silicon nitride and indium phosphide to enable high-speed, long-distance secure quantum communication with low error rates.

Contribution

It introduces a novel hybrid integration approach that combines silicon nitride and indium phosphide materials for quantum photonic circuits, enabling on-chip active encoding and decoding at GHz speeds.

Findings

Achieved secure bit rates of 1.82 Mbps over 10 dB channel attenuation

Demonstrated positive secure key rates over 250 km of fibre

Maintained sub-1% quantum bit error rates over long distances

Abstract

Quantum photonic technologies, such as quantum key distribution, are already benefiting greatly from the rise of integrated photonics. However, the flexibility in design of these systems is often restricted by the properties of the integration material platforms. Here, we overcome this choice by using hybrid integration of ultra-low-loss silicon nitride waveguides with indium phosphide electro-optic modulators to produce high-performance quantum key distribution transceiver chips. Access to the best properties of both materials allows us to achieve active encoding and decoding of photonic qubits on-chip at GHz speeds and with sub-1% quantum bit error rates over long fibre distances. We demonstrate bidirectional secure bit rates of 1.82 Mbps over 10 dB channel attenuation and positive secure key rates out to 250 km of fibre. The results support the imminent utility of hybrid integration for quantum photonic circuits and the wider field of photonics.