Team hails quantum leap in telecomms security

In a paper published in the journal Nature Communications, researchers from the Universities of Glasgow, Stanford, Tokyo and Würzburg describe how the phenomenon of quantum entanglement  - which enables particles that are separated to share properties - could be used to encode data and send it over long distances.

Scientists have previously demonstrated that quantum entanglement can enable the exchange of information over short distances.

This process also allows information to be encoded in quantum particles, similar to the way in which the ones and zeroes (known as bits) of digital communication are used to encode all kinds of data.

Two computers sharing quantum information are much more secure, as any interception by a third party will change the properties of the data itself, allowing easy detection by the intended recipient. 

In a demonstration of how quantum computers might be able to communicate with each over long distances via a so-called “Quantum internet” the team achieved a world-first by transmitting a quantum bit (qubit) along a 2km length of standard fibre optic cable.

The team’s coordinator, Glasgow University researcher Dr Chandra Mouli Natarajan, explained that this was achieved by creating correlations between the spin of an electron stored in a tiny crystal of semiconducting material known as a ‘quantum dot’ and the arrival time of a single photon across two kilometres of standard fiber-optic cable.

“Quantum dots are commonly used to generate individual photons,” explained Dr Natarajan. “However, these types of photons can’t travel very far in the standard fiber optic network used in telecommunications industry because they tend to leak out along the way. Quantum dots are also capable of trapping electrons, and previously our research group had shown that entanglement can be created between the trapped electron and a photon generated by the quantum dot.

“For the first time, we were able to establish a long-distance correlation between the trapped electron and the photon in the telecommunications band.

“The physics behind quantum communication, by their very nature, make data transfer utterly secure,” he added. “Any tampering with either side of the communication will be immediately apparent because it will affect the quantum correlations. Our work is an important step towards creating architectures for the future hybrid quantum internet.”