Quantum communication breakthrough: goes subsea, international

Technology News | October 3, 2023

By Peter Clarke

Optoelectronics Interconnect & cables Quantum photonics

Researchers have demonstrated quantum communications can be achieved over a sub-sea optical fibre cable between the United Kingdom and the Republic of Ireland.

The team, led by Professor Marco Lucamarini from the University of York, ran a series of experiments over a cable that runs between Portrane and Southport. Until now, no quantum link has ever been established between the two countries, nor on a span stretching this length on a subsea fibre optic cable, according to euNetworks Fiber UK Ltd. which operates the 224km Rockabill subsea network.

The successful demonstration between the UK and Ireland pushes the boundaries of quantum communications and the security of data from eavesdropping.

The research team from the University of York worked in collaboration with the Quantum Communications Hub of the ESPRC and euNetworks.

Quantum communication operates on the principle that particles of light can transmit data along optical cables in a highly fragile state. But the particles collapse if interfered with by someone trying to manipulate or steal private data, such as bank information, in transit.

“Many large companies and organisations are interested in quantum communications to secure their data, but it has limitations, particularly the distance it can travel,” said Professor Marco Lucamarini, in a statement issued by euNetworks and the University of York. “The longer the distance, the more likely it is that the photon – the particles of light that we use as carriers of quantum information – are lost, absorbed or scattered in the channel, which reduces the chances of the information reaching its target. This presents a problem when organisations need to send private digital information to other cities or other countries, where the additional challenge could also be an ocean between the communications’ start and end point.”

Special cable

The Rockabill subsea cable was key to the research. It provides an ultra-low loss fiber optic subsea cable with low latency, low attenuation and spans the 224 kilometers between Southport and Portrane without amplification or repeaters.

Both single and entangled photons were transported in the experiments the optical phase measured for use in twin-field and continuous-variable Quantum Key Distribution (QKD). The success of the experiments was largely due to highly sensitive detectors deployed at the Southport endpoint of the cable to reduce environmental noise levels.

Professor Lucamarini said: “This project also advances the real-world integration of quantum communication technology into existing global telecommunications and network infrastructure – taking it out of the lab into a ‘real-world’ scenario.”

More experiments are scheduled to be carried out using the same cable to prepare for the offering of quantum security on standard communications for those sending data between the UK and Ireland.

The project is due to be presented at the NATO Symposium on Quantum Technology for Defence and Security in Amsterdam on October 3.