Researchers at the Quantum Communications Hub in Scotland have used quantum key distribution to secure a four-way conference call for the first time.
QKD uses quantum mechanics to secure communications, but so far has been point to point. Researchers in Bristol last year showed distributed QKD on a network.
The Scottish demonstration, led by Hub researchers based at Heriot-Watt University with a team from Institut für Theoretische Physik at the Heinrich Heine University in Düsseldorf, showed multi-party entanglement where encryption keys were shared simultaneously between the four parties, through a process known as Quantum Conference Key Agreement (CKA) over 50 km of optical fibre.
The project distributed four-photon Greenberger-Horne-Zeilinger (GHZ) states, generated by high-brightness telecom photon-pair sources, over optical fibre with combined lengths of up to 50 km and then perform multiuser error correction and privacy amplification. This created 1.5 × 106 bits of secure key, which are used to encrypt and securely share an image between four users in a conference transmission.
“Our work highlights a previously unexplored protocol tailored for multinode networks leveraging low-noise, long-distance transmission of GHZ states that will pave the way for future multiparty quantum information processing applications,” said Professor Alessandro Fedrizzi, who led the team at Heriot-Watt.
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