Bright Source of High-Dimensional Temporal Entanglement

TL;DR

This paper presents a high-brightness, stable source of high-dimensional time-bin entangled photons, validated with a new witness and used in a noise-resilient QKD protocol, enabling high key rates in challenging environments.

Contribution

We developed a robust, high-brightness source of high-dimensional entangled photons and introduced a flexible evaluation method for optimizing quantum key distribution performance.

Findings

High key rates are achievable with large dimensionalities.

The source demonstrates long-term stability and low complexity.

The evaluation method allows parameter optimization under environmental noise.

Abstract

High-dimensional entanglement is considered to hold great potential for quantum key distribution (QKD) in high-loss and -noise scenarios. To harness its robustness, we construct a source for high-dimensional time-bin entangled photons optimized for high brightness, low complexity, and long-term stability. We certify the generated high-dimensional entanglement with a new witness employing nested Franson interferometry. Finally, we obtain key rates using a novel, noise-resilient QKD protocol. Our flexible evaluation method, centered around discretizations of the time stream, enables the same dataset to be processed while varying parameters such as state dimensionality and time bin length, allowing optimization of performance under given environmental conditions. Our results indicate regions within the accessible parameter space where high key rates per time are achievable for dimensionalities larger than two.