Tomography increases key rates of quantum-key-distribution protocols

TL;DR

This paper demonstrates that incorporating quantum tomography into classical processing enhances key rates in quantum key distribution protocols, surpassing standard methods and enabling positive key rates even at higher error levels.

Contribution

It introduces a practical classical processing method utilizing quantum tomography that improves key rates in BB84 and six-state protocols over standard approaches.

Findings

Proposed processing achieves at least as high key rate as standard methods.

In certain channels, the key rate is strictly higher with the new processing.

Allows positive key rates beyond the 25% error threshold.

Abstract

We construct a practically implementable classical processing for the BB84 protocol and the six-state protocol that fully utilizes the accurate channel estimation method, which is also known as the quantum tomography. Our proposed processing yields at least as high key rate as the standard processing by Shor and Preskill. We show two examples of quantum channels over which the key rate of our proposed processing is strictly higher than the standard processing. In the second example, the BB84 protocol with our proposed processing yields a positive key rate even though the so-called error rate is higher than the 25% limit.