Engineers at the University of Glasgow have developed a new method of quantum key distribution (QKD) that could help secure communications in the quantum-powered internet of the future — and it doesn’t rely on the fibre-optic infrastructure that underpins most current approaches.
The team, based in the James Watt School of Engineering, have simulated a system using coherent terahertz waves transmitted via wireless communications technology adapted from 4G, 5G, and wifi networks. Their findings, published in IEEE Transactions on Quantum Engineering, suggest the approach could offer a high-fidelity, energy-efficient alternative to conventional QKD platforms built around laser beams and fibre-optic cables.
The research arrives at a critical moment for the global cybersecurity community. While today’s internet traffic is protected by encryption standards such as Transport Layer Security, quantum computers — capable of vastly outperforming conventional machines — are widely expected to render many of those protections obsolete. QKD is seen as one of the most promising defences, using the laws of quantum physics to make interception detectable and encryption effectively unbreakable. The Glasgow work is significant because it explores whether terahertz waves can carry that security layer without the need for optical infrastructure — a constraint that limits where and how quantum networks can be deployed.
Dr Kaveh Delfanazari, the paper’s corresponding author, explained the challenge facing researchers worldwide: “Building the quantum internet is a major scientific and engineering challenge because quantum computers are highly sensitive to thermal fluctuations, electromagnetic noise, and environmental disturbances. These effects can rapidly destroy fragile quantum states, making reliable and secure communication between quantum systems extremely difficult. Overcoming this challenge is essential for enabling large-scale quantum networks, distributed quantum computing, and next-generation secure communications.”
The proposed hardware system is built around superconducting Josephson junction coherent emitters — compact, low-power devices that generate quantum terahertz waves. The signal is then transmitted using Orthogonal Frequency-Division Multiplexing (OFDM), a technique already proven in 4G, 5G, and wifi, which splits the signal across parallel subcarriers to increase the volume of QKD-secured data sent in a single transmission.
The team simulated the system’s performance across three distinct environments. In open air — where atmospheric water vapour limits terahertz performance — the system achieved coherent transmission over around four metres, sufficient for use inside data centres or quantum computers themselves. In space, free from atmospheric interference, the simulations showed secure communications could extend beyond 100 kilometres. In cryogenically-cooled cables of the kind used inside quantum hardware, secure messages could travel up to 26 kilometres.
Dr Delfanazari said: “Here at the University of Glasgow, we’ve been working on terahertz quantum communication technologies for some time. With this project, we were keen to explore the potential of terahertz tech as a building block for the quantum future that scientists around the world are laying the foundations for today. This is a concept paper, but it’s backed by thorough simulation, and we’re excited by the results.”
PhD student Mingqi Zhang, the paper’s first author, said the team is now moving beyond simulation: “We’re confident that our modelling work shows clearly the potential of terahertz technologies to enable high-performance quantum key distribution in three challenging environments. The next steps for us are to start building physical systems which we can test in the lab and out in the real world, helping us to validate our results and start to overcome some of the limitations we’ve identified in our simulations. We’ve already started taking steps to making that happen, and we’re looking forward to continuing our research in this promising area.”
The research was supported by funding from the Royal Academy of Engineering, the Royal Society of Edinburgh, and the Royal Society — the latter two underlining Scotland’s continued role as a hub for frontier science with real-world security implications.
Scotland has steadily built credibility in deep tech and quantum-adjacent research, and work like this from Glasgow positions the country well as governments and enterprises begin seriously planning quantum network infrastructure. Whether the terahertz approach ultimately scales to real-world deployment, the University of Glasgow is helping shape the intellectual foundations of what comes next.
The full paper, Orthogonal Frequency-Division Multiplexing Continuous-Variable Terahertz QKD for Large-Scale Wireless Quantum Communication, is published in IEEE Transactions on Quantum Engineering.
