The fibre carries data but also encryption keys in the form of quantums of light that cannot be intercepted.
“This first industrial deployment of a quantum-secure network in the UK is a significant milestone as we move towards a quantum-ready economy,” said Andrew Lord, a physicist who is BT’s head of optical technology, who said it was a demonstration of “the ultra-secure nature of quantum cryptography”.
Quantum key distribution (QKD) uses one of the weirder features of quantum physics. First described by Albert Einstein in 1935, quantum entanglement means that pairs of particles – photons of light in this case – are related even if they are separated by a great distance.
It was, Einstein is reputed to have said, “spooky action at a distance”. Most people working in telecoms research haven’t needed even to think about it for years. “I had to get out my ancient university textbooks,” said Lord when he spoke to Capacity in 2018.
This test connects transmitting between the National Composites Centre (NCC) and the Centre for Modelling & Simulation (CFMS), two research organisations in Bristol. The encrypted link, which also connects the Univeristy of Bristol, uses standard fibre from Openreach, BT’s last-mile network.
According to BT, Toshiba’s QKD system enables the distribution of thousands of cryptographic keys per second. “Its innovative multiplexing compatibility allows the data and the quantum keys to be transmitted on the same fibre, eliminating the need for costly dedicated infrastructure for key distribution,” said the company.
“While this first deployment covers a range of 6km, the current maximum range extends up to 120km – allowing ultra-secure data transmission across major metropolitan environments.”
Andrew Shields, head of quantum technology at Toshiba Europe, said: “With the UK government’s assertion earlier this month that it wants to be the world’s first quantum-ready economy, quantum-secure networks are vital to it achieving this ambition, and we’re excited to be at the forefront of making this a reality.”
