Scientists have developed a method of securely communicating between multiple quantum devices, bringing a large-scale, unhackable network closer to reality. To date, communicating via quantum networks has only been possible between two devices of known provenance that have been built securely.
"We're in a technology arms race of sorts. When quantum computers are fully developed, they will break much of today's encryption whose security is only based on mathematical assumptions," said Ciaran Lee, from University College London in the UK.
"To pre-emptively solve this, we are working on new ways of communicating through large networks that don't rely on assumptions, but instead use the quantum laws of physics to ensure security, which would need to be broken to hack the encryption," said Lee, lead author of the study published in the journal Physical Review Letters.
"Our approach works for a general network where you don't need to trust the manufacturer of the device or network for secrecy to be guaranteed," said Matty Hoban, from University of Oxford in the UK.
"Our method works by using the network's structure to limit what an eavesdropper can learn," Hoban said. The approach bridges the gap between the theoretical promise of perfect security guaranteed by the laws of quantum physics and the practical implementation of such security in large networks.
It tests the security of the quantum devices prior to engaging in communications with the whole network. It does this by checking if the correlations between devices in the network are intrinsically quantum and cannot have been created by another means.
The correlations are used to establish secret keys which can be used to encrypt any desired communication. Security is ensured by the unique property that quantum correlations can only be shared between the devices that created them, ensuring no hacker can learn the key.
"Our work can be thought of as creating the software that will run on hardware currently being built to realise the potential of quantum communications," Lee said.