Quantum Key Distribution without sending a Quantum Signal

TL;DR

This paper proposes a novel quantum key distribution protocol that leverages relativistic quantum field theory to establish secure keys without transmitting quantum signals, relying on spacetime entanglement.

Contribution

It introduces a practical protocol for secure key distribution without quantum signals, based on relativistic entanglement, expanding quantum communication possibilities.

Findings

Secure key distribution without quantum signals is theoretically possible using spacetime entanglement.

The protocol is feasible with current horizon technology in free space.

Potential implementation with microwave technology in the near term.

Abstract

Quantum Key Distribution is a quantum communication technique in which random numbers are encoded on quantum systems, usually photons, and sent from one party, Alice, to another, Bob. Using the data sent via the quantum signals, supplemented by classical communication, it is possible for Alice and Bob to share an unconditionally secure secret key. This is not possible if only classical signals are sent. Whilst this last statement is a long standing result from quantum information theory it turns out only to be true in a non-relativistic setting. If relativistic quantum field theory is considered we show it is possible to distribute an unconditionally secure secret key without sending a quantum signal, instead harnessing the intrinsic entanglement between different regions of space time. The protocol is practical in free space given horizon technology and might be testable in principle in the near term using microwave technology.