Classical light steering leading to quantum-like security

TL;DR

This paper demonstrates that classical light can exhibit single system steering, a quantum-like property, which can be utilized for secure key distribution similar to quantum protocols.

Contribution

It reveals that classical optics can exhibit quantum-like steering and security features, bridging classical and quantum information concepts.

Findings

Classical light can demonstrate single system steering.

A steering criterion for coherent states is derived.

The security bound for BB84 under cloning attack is calculated.

Abstract

We show how single system steering can be exhibited by classical light, a feature originating from superposition in classical optics that also enables entanglement and Bell-violation by classical light beams. Single system steering is the temporal analogue of Einstein-Podolsky-Rosen (EPR) steering in the quantum domain, enabling control of the state of a remote system, and can hence be connected to the security of secret key generation between two remote parties. We derive the steering criterion for a single mode coherent state when displaced parity measurements are performed at two different times. The security bound of the Bennett-Brassard 1984 (BB84) protocol under the gaussian cloning attack is calculated to yield an, in principle, ideal and quantum-like key rate using a fine-grained uncertainty relation corresponding to the classical phase space.