Quantum leap for photon entanglement could revolutionise secure communications

A breakthrough in the development of quantum-enhanced optical systems could pave the way for advances in encryption, communication and measurement, scientists say. In a new paper published today in the journal Science Advances, a group of researchers, led by Matteo Clerici at the University of Glasgow's James Watt School of Engineering and colleagues from the UK, Japan and Germany, demonstrates a new method of generating and detecting quantum-entangled photons at a wavelength of 2.1 micrometres. The unique, non-classical properties of entangled photons are used in applications including quantum key distribution, which makes uncrackable communications between two parties possible. Methods of entangling photons at shorter wavelengths of between 700 and 1550 nanometres are already well-established. However, those wavelengths are vulnerable to interference from the sun's light when they are transmitted over open air, making them difficult to use in applications such as secure satellite-to-ground and satellite-to-satellite communications. The Glasgow-led team's new method of generating entangled photons further into the infrared at two micrometres wavelength could help overcome these problems for the first time. Dr Matteo Clerici, Senior Lecturer at the University of Glasgow, said: "What we have been able to do for the first time is carve out a band in the electromagnetic spectrum where the entangled particles we produce are less likely to be affected by background solar radiation when they're transmitted across free space.