Optimal analysis of ultra broadband energy-time entanglement for high bit-rate dense wavelength division multiplexed quantum networks

TL;DR

This paper presents an efficient experimental method for measuring ultra broadband energy-time entanglement over 80 nm bandwidth, significantly enhancing quantum key distribution capabilities with minimal resources.

Contribution

It introduces a cost-effective, single-source measurement scheme with optimized interferometer balancing for high-bandwidth entanglement analysis.

Findings

Achieved energy-time entanglement measurement over 80 nm spectral bandwidth.

Demonstrated low quantum bit error rate below 0.5%.

Showed that proper interferometer unbalancing maximizes analysis bandwidth.

Abstract

We demonstrate an experimental method for measuring energy-time entanglement over almost 80 nm spectral bandwidth in a single shot with a quantum bit error rate below 0.5%. Our scheme is extremely cost-effective and efficient in terms of resources as it employs only one source of entangled photons and one fixed unbalanced interferometer per phase-coded analysis basis. We show that the maximum analysis spectral bandwidth is obtained when the analysis interferometers are properly unbalanced, a strategy which can be straightforwardly applied to most of today's experiments based on energy-time and time-bin entanglement. Our scheme has therefore a great potential for boosting bit rates and reducing the resource overhead of future entanglement-based quantum key distribution systems.