Experimental demonstrations of unconditional security in a purely classical regime

TL;DR

This paper reports the first experimental demonstration of a classical key distribution protocol that achieves unconditional security through path superposition and reversible transformations, offering an alternative to quantum-based methods.

Contribution

It provides the first experimental validation of a purely classical, unconditionally secure key distribution protocol based on path superposition.

Findings

Successful experimental implementation of USCKD protocol

Demonstration of unconditional security in classical regime

Potential for classical alternatives to quantum key distribution

Abstract

So far, unconditional security in key distribution processes has been confined to quantum key distribution (QKD) protocols based on the no-cloning theorem of nonorthogonal bases. Recently, a completely different approach, the unconditionally secured classical key distribution (USCKD), has been proposed for unconditional security in the purely classical regime. Unlike QKD, both classical channels and orthogonal bases are key ingredients in USCKD, where unconditional security is provided by deterministic randomness via path superposition-based reversible unitary transformations in a coupled Mach-Zehnder interferometer. Here, the first experimental demonstration of the USCKD protocol is presented.