High-Dimensional Quantum Key Distribution based on Multicore Fiber using Silicon Photonic Integrated Circuits

TL;DR

This paper demonstrates a novel high-dimensional quantum key distribution protocol using multicore fiber and silicon photonic circuits, significantly increasing information capacity and stability over traditional binary QKD methods.

Contribution

First experimental demonstration of high-dimensional QKD with multicore fiber and integrated silicon photonics, surpassing traditional information efficiency limits.

Findings

Achieved low quantum bit error rate below attack thresholds.

Realized three mutually unbiased bases in four-dimensional space.

Enabled stable, compact manipulation of high-dimensional quantum states.

Abstract

Quantum Key Distribution (QKD) provides an efficient means to exchange information in an unconditionally secure way. Historically, QKD protocols have been based on binary signal formats, such as two polarisation states, and the transmitted information efficiency of the quantum key is intrinsically limited to 1 bit/photon. Here we propose and experimentally demonstrate, for the first time, a high-dimensional QKD protocol based on space division multiplexing in multicore fiber using silicon photonic integrated lightwave circuits. We successfully realized three mutually unbiased bases in a four-dimensional Hilbert space, and achieved low and stable quantum bit error rate well below both coherent attack and individual attack limits. Compared to previous demonstrations, the use of a multicore fiber in our protocol provides a much more efficient way to create high-dimensional quantum states, and enables breaking the information efficiency limit of traditional QKD protocols. In addition, the silicon photonic circuits used in our work integrate variable optical attenuators, highly efficient multicore fiber couplers, and Mach-Zehnder interferometers, enabling manipulating high-dimensional quantum states in a compact and stable means. Our demonstration pave the way to utilize state-of-the-art multicore fibers for long distance high-dimensional QKD, and boost silicon photonics for high information efficiency quantum communications.