Wireless quantum key distribution at terahertz frequencies: Opportunities and challenges

Abstract Quantum key distribution (QKD) is one of the major applications of quantum information technology. It can provide ultra‐secure key distribution with security guaranteed by the laws of quantum physics. Quantum key distribution is necessary to protect data transmission from quantum computing attacks in future communication networks. The laws of quantum mechanics dictate that as opposed to microwave frequencies, quantum coherence is preserved at room temperatures for terahertz (THz) frequencies. This makes the THz band a promising solution for room‐temperature QKD implementation in future wireless communication networks. The authors present the principles of continuous variable QKD (CV‐QKD) systems and review the latest developments in the design and analysis of CV‐QKD systems operating at microwave and THz frequencies. The authors also discuss how multiple‐input multiple‐output transmission can be incorporated into the quantum communications framework to improve the secret key rates and increase the coverage distances of the THz CV‐QKD system. Furthermore, major hardware challenges that must be surmounted to practically realise THz CV‐QKD systems are highlighted.