Large-Alphabet Time-Frequency Entangled Quantum Key Distribution by means of Time-to-Frequency Conversion

TL;DR

This paper presents a new time-frequency quantum key distribution scheme using photon pairs entangled in conjugate degrees of freedom, enabling large-alphabet encoding with realistic components through time-to-frequency conversion.

Contribution

It introduces a novel TFQKD scheme based on spectral detection and phase modulation, linking it to finite-dimensional QKD protocols and analyzing dark count effects.

Findings

Enables large-alphabet encoding in TFQKD

Provides security analysis related to finite-dimensional protocols

Assesses impact of dark counts on secure key size

Abstract

We introduce a novel time-frequency quantum key distribution (TFQKD) scheme based on photon pairs entangled in these two conjugate degrees of freedom. The scheme uses spectral detection and phase modulation to enable measurements in the temporal basis by means of time-to-frequency conversion. This allows large-alphabet encoding to be implemented with realistic components. A general security analysis for TFQKD with binned measurements reveals a close connection with finite-dimensional QKD protocols and enables analysis of the effects of dark counts on the secure key size.