How decoherence affects the security of BB84 quantum key distribution protocol

TL;DR

This paper explores how quantum decoherence, explained through quantum Darwinism, can lead to information leakage in BB84 quantum key distribution, affecting its security and suggesting ways to improve shielding.

Contribution

It introduces a decoherence-based analysis of information leakage in BB84, linking quantum Darwinism to practical security considerations and environmental organization.

Findings

Quantum Darwinism explains information leakage during measurement.

Environmental layering influences the spread of quantum information.

Proper shielding can mitigate information leakage in quantum cryptography.

Abstract

We present how the mechanisms of quantum Darwinism allow for the leakage of information in the standard BB84 quantum key distribution protocol, a paradigmatic prepare and measure quantum cryptography scenario. We work within the decoherence theory framework and employ the model of measurements provided by quantum Darwinism. We investigate how much of the information about the results crucial for the cryptographic key to be kept secret is leaked during the quantum measurement process and subsequently how much of that information might be later obtained by an eavesdropper using a type of a so-called Van Eck side-channel wiretapping. We also show how the security can be affected by different ways of organizing the surrounding environment into layers, e.g. rooms or other divisions affecting the spread of quantum information in the environment and its interaction, paving a venue to potential enhancements, and insight into proper engineering of shieldings for cryptographical devices.