Topological Device-Independent Quantum Key Distribution Using Majorana-Based Qubits

TL;DR

This paper develops a theoretical framework for device-independent quantum key distribution using Majorana-based qubits, addressing hardware noise, security proofs, and practical constraints for topological quantum networks.

Contribution

It introduces a hardware-native error model, a loss-disciplined protocol, and a security proof tailored for Majorana zero mode processors in DI-QKD.

Findings

Majorana qubits enable simplified Bell measurements for DI-QKD.

Poisoning rates critically limit secure communication distances.

Hardware thresholds like poisoning suppression are essential for viable quantum networks.

Abstract

Device-independent quantum key distribution (DI-QKD) provides the highest level of cryptographic security by certifying secrecy through observed Bell inequality violations, independent of the internal device physics. However, the transition from theory to practice is obstructed by the dual challenge of closing the detection loophole and achieving viable key rates over fiber distances. In this paper, we present a comprehensive theoretical framework for DI-QKD implemented on topological Majorana Zero Mode (MZM) processors. While MZMs offer a native parity-readout basis that simplifies Bell-state measurement, their viability as QKD nodes is fundamentally constrained by the interplay between storage latency and quasiparticle poisoning. We bridge the gap between microscopic hardware noise and macroscopic security by: (i) developing a hardware-native error model that maps MZM-specific processes, including poisoning rates, braid infidelities, and readout anisotropy, directly to the CHSH Bell parameter $S$; (ii) introducing a loss-disciplined protocol that monitors setting-conditional efficiencies to strictly enforce detection-loophole closure in a heralded architecture; and (iii) providing a composable finite-size security proof based on the Entropy Accumulation Theorem (EAT). Our analysis reveals that while topological protection stabilizes the system against calibration drift, the achievable secure distance is strictly bounded by the poisoning-induced visibility collapse during the photonic round-trip time. We identify specific hardware thresholds, particularly the suppression of poisoning rates to $\Gamma_p \tau_{\text{max}} \ll 1$ and high-fidelity sensor integration, as the critical path for viable topological quantum networks.