Quantum key distribution without sending a quantum signal

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. While 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.

Quantum Temporal Superposition: The Case of Quantum Field Theory

“…We consider the process of entanglement harvesting from the quantum field vacuum, which is well-understood in flat spacetime [30,33]. Entanglement harvesting has attracted much interest for its foundational and applicative relevance [30,[33][34][35][36][37][38][39][40], with possible implications for the black hole information paradox and quantum gravity [32, [41][42][43][44][45][46][47].…”

Effects of gravity on continuous-variable quantum key distribution

“…The efforts have culminated in the work [16], whose method has been succesfully extended [17] and applied to CV quantum information protocols [18]. Several previous works [19][20][21] have meaningfully investigated the effect of the acceleration on a specific cryptographic scheme, where only one of the parties was allowed to accelerate, and the effect of gravity on information transmission [22][23][24]. Here, we aim to extend those studies to various QKD schemes and to the general scenario in which both Alice and Bob are affected by acceleration or gravity.…”

Spacetime diamonds

“…More promising candidates might be artificial atoms such as the superconducting qubits and quantum dots [13].…”