Multi-dimensional frequency-bin entanglement-based quantum key distribution network

TL;DR

This paper demonstrates a multi-dimensional frequency-bin entanglement-based quantum key distribution network using silicon microresonators, achieving high secure key rates and long-distance communication with stable, multi-channel operation.

Contribution

It introduces a novel multi-dimensional frequency-bin entanglement source and demonstrates its application in a scalable, stable quantum key distribution network over metropolitan fiber links.

Findings

Secure key rate of 1374 bits/sec with qutrits

Estimated communication range of 295 km with qubits

Access to 80 frequency modes and 21 quantum channels

Abstract

Quantum networks enhance quantum communication schemes and link multiple users over large areas. Harnessing high dimensional quantum states - i.e. qu-d-its - allows for a denser transfer of information with increased robustness to noise compared to qubits. Frequency encoding enables access to such qu-d-its at telecom wavelengths, while manipulating quantum information with off-the-shelf fibered devices. We use a low free spectral range silicon microresonator to generate Bell states of dimension d=2 (qubits) and d=3 (qutrits) via spontaneous four wave mixing, to implement and optimize a multi-dimensional frequency-bin entanglement-based quantum key distribution network. We tune the source (via pump power), the signal processing (via coincidence window size) and qu-d-it encoding (d=2 or 3) using a single fibered hardware based on Fourier-transform pulse shaping and electro-optic modulation depending on interconnection lengths. We achieve secure key rates of 1374 bit/s with qutrits, and estimate the communication range to 295 km with qubits. We access up to 80 frequency modes, resulting in 21 quantum channels, that provide stable communication over more than 21 hours. We demonstrate a competitive communication range in a multi-dimensional entanglement-based quantum key distribution network that lays the groundwork for larger dimensionality implementations deployed on metropolitan fiber links.