Quantum effects can deliver long-distance secure comms, researchers report

November 25, 2015 // By Graham Prophet
In a newly-published paper (24th November 2015) in the journal Nature Communications, researchers from the Universities of Glasgow, Stanford, Tokyo and Würzburg describe how they have implemented a novel tool for a long-distance telecommunication link which is impossible for hackers to breach.

The technique could also underpin the creation of a new form of ‘quantum internet’; the telecommunications technique, which harnesses quantum technology, could lead to a much more secure form of worldwide internet communications, the scientists have reported.

Scientists have previously used the phenomenon of quantum entanglement – also known as ‘spooky action at a distance’ - to allow the exchange of information over short distances. Entanglement allows particles which are physically separated to nonetheless share properties – for example, the direction of one electron’s spin will be related to the direction of spin of its entangled partner.

This process of entanglement also allows encoding of information in quantum particles, similar to the way in which the bits of conventional digital communication are used. 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.

To allow quantum computers to communicate with each other, a new type of quantum network capable of transmitting the special quantum bits (known as qubits) over long distances will need to be built.

The team, co-ordinated by University of Glasgow postdoctoral research fellow Dr Chandra Mouli Natarajan, together with colleagues at Stanford, managed to create long distance telecommunication link for a stationary quantum bit for the first time. They created correlations between a spin of an electron stored in a ‘quantum dot’ semiconducting material, and the arrival time of single photon across two kilometres of standard fibre-optic cable.

Dr Natarajan said: “Our work is built on three components. The first is quantum dots – special crystals just a few nanometers in size. The second is a tailored waveguide, which allows us to precisely control and convert the energy of individual photons. The final component is a highly-sensitive detector capable of sensing single photons.

“Quantum dots are commonly used to generate individual photons. However, these types of