Terahertz Quantum Cryptography

TL;DR

This paper demonstrates the feasibility of quantum key distribution in the terahertz frequency range, analyzing key rates and practical hardware considerations for secure wireless communication at these frequencies.

Contribution

It introduces the concept of THz quantum cryptography, deriving secret key rates and proposing a hardware architecture for secure communication in this spectrum.

Findings

Quantum key distribution is feasible in the THz regime.

High-rate THz quantum cryptography can operate over meters to hundreds of meters.

Thermal noise and atmospheric absorption are main challenges at different frequencies.

Abstract

A well-known empirical rule for the demand of wireless communication systems is that of Edholm's law of bandwidth. It states that the demand for bandwidth in wireless short-range communications doubles every 18 months. With the growing demand for bandwidth and the decreasing cell size of wireless systems, terahertz (THz) communication systems are expected to become increasingly important in modern day applications. With this expectation comes the need for protecting users' privacy and security in the best way possible. With that in mind, we show that quantum key distribution can operate in the THz regime and we derive the relevant secret key rates against realistic collective attacks. In the extended THz range (from 0.1 to 50 THz), we find that below 1 THz, the main detrimental factor is thermal noise, while at higher frequencies it is atmospheric absorption. Our results show that high-rate THz quantum cryptography is possible over distances varying from a few meters using direct reconciliation, to about 220m via reverse reconciliation. We also give a specific example of the physical hardware and architecture that could be used to realize our THz quantum key distribution scheme.