Time-Entanglement QKD: Secret Key Rates and Information Reconciliation Coding

TL;DR

This paper analyzes the impact of detector jitter errors on time-entanglement QKD secret key rates and develops coding strategies for efficient information reconciliation to maximize secure key generation.

Contribution

It quantifies secret key rates considering detector jitter and introduces coding methods for improved information reconciliation in time-entanglement QKD.

Findings

Secret key rates decrease with increasing detector jitter.

Proposed coding schemes approach theoretical key rate limits.

Enhanced reconciliation methods improve secure key throughput.

Abstract

In time entanglement-based quantum key distribution (QKD), Alice and Bob extract the raw key bits from the (identical) arrival times of entangled photon pairs by time-binning. Each of them individually discretizes time into bins and groups them into frames. They retain only the frames with a single occupied bin. Thus, Alice and Bob can use the position of the occupied bin within a frame to generate random key bits, as in PPM modulation. Because of entanglement, their occupied bins and their keys should be identical. However, practical photon detectors suffer from time jitter errors. These errors cause discrepancies between Alice's and Bob's keys. Alice sends information to Bob through the public channel to reconcile the keys. The amount of information determines the secret key rate. This paper computes the secret key rates possible with detector jitter errors and constructs codes for information reconciliation to approach these rates.