Hybrid ququart-encoded quantum cryptography protected by Kochen-Specker contextuality

TL;DR

This paper introduces a quantum cryptography scheme using hybrid ququarts protected by Kochen-Specker contextuality, which offers security against classical imitation attacks without relying on entanglement, and analyzes its noise tolerance and implementation.

Contribution

It presents a novel cryptographic protocol leveraging Kochen-Specker contextuality with hybrid ququarts and provides a photonic realization and noise analysis.

Findings

Maximum noise tolerance for security is characterized.

A practical photonic implementation using polarization and orbital angular momentum is described.

The scheme is secure against classical imitation attacks without entanglement.

Abstract

Quantum cryptographic protocols based on complementarity are nonsecure against attacks in which complementarity is imitated with classical resources. The Kochen-Specker (KS) theorem provides protection against these attacks, without requiring entanglement or spatially separated composite systems. We analyze the maximum tolerated noise to guarantee the security of a KS-protected cryptographic scheme against these attacks, and describe a photonic realization of this scheme using hybrid ququarts defined by the polarization and orbital angular momentum of single photons.