Researcher transmit quantum information over 250-km-long optical fibres

New Delhi, Apr 26 (PTI) In a new research, quantum messages were successfully sent over 250 kilometres of regular telecommunications network, suggesting a method for quantum-communication technology can be implemented in real-world settings.

Published in the journal Nature, the study documents the first instance of quantum communications using existing, commercially available telecommunication infrastructure Researchers from Toshiba Europe Limited, UK, suggested that quantum communications -- which makes use of principles of quantum physics to transmit information -- can be achieved in real-world conditions.

The system of communication, such as a quantum internet, is seen as promising for enabling a safer, secure way of transmitting information.

One of the techniques employed to transmit information in quantum network is 'quantum key distribution'. It involves two qubits -- one qubit is a fundamental unit of information -- which are entangled in a way that the code required to break their link is shared only between the two.

The researchers explained that by exploiting the property of 'coherence' of light, in which waves of light interact with each other in a predictable pattern, a quantum network can be expanded to cover a wider area.

However, this scalability has been limited by the need for specialised equipment, such as cryogenic coolers, for maintaining an absolute zero Kelvin (or -273 degrees Celsius) temperature, they said.

In this research paper, the authors describe an approach that allows quantum information to be transmitted through commercially available optical fibres, without the need for cryogenic cooling.

The quantum communications system developed by the team was deployed over three telecommunication data centres in Germany -- Frankfurt, Kehl and Kirchfeld -- connected by 254 kilometres of commercial optical fibre cables.

"We deployed our system across three data centres in Germany, spanning from Frankfurt to Kehl, that were connected by 254 kilometres of optical fibre," the authors wrote.

Existing telecommunications infrastructure was used for "achieving real-world, practical quantum key distribution over a long distance," they wrote.

The findings show that "coherent quantum-communication technology can be implemented in real-world settings and have useful applications," the team said. PTI KRS NB