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First time test of UK / Ireland quantum communications with underwater cable

Posted on 3 October 2023

Researchers have successfully tested a fibre-optic cable to pass quantum communications under the Irish Sea between the Republic of Ireland and England.

The researchers exploited a new and unique underwater cable system between England and Ireland,

It is the longest stretch of fibre-optic cable ever used to enable quantum communications underwater, and the first time a quantum link has ever been tested between Ireland and the UK.

The research team, led by Professor Marco Lucamarini from the University of York’s Institute for Safe Autonomy and School of Physics, Engineering and Technology, ran a series of experiments using a network cable named Rockabill

This network, owned and operated by bandwidth infrastructure provider, euNetworks, is one of the newest commercial optical fibre systems in operation and connects Ireland to the United Kingdom, running 224 kilometres between Portrane in Ireland and Southport in the UK. 

Overcoming limitations

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

Professor Lucamarini said: “Many large companies and organisations are interested in quantum communications to secure their data, but it has limitations, in particular the distance it can travel. 

“The longer the distance, the more likely it is that photons - 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 information to other countries, where the additional challenge could be an ocean between the communications’ start and end point.” 

Unique system

To overcome this limitation, the researchers exploited a new and unique underwater cable system between England and Ireland, reducing the chances of the quantum information being lost, allowing the particles that enter the link to reach the other end of the communication channel. 

The same link also has very little time delay, which means a fast connection in sending and receiving data, which is crucial for financial transactions for example. 

Professor Lucamarini said: “This is a truly exciting step forward in realising the full potential of quantum communications and for the future of securing private data in an environment that is shaping the so-called “quantum internet”. 

“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.”


The success of the experiments was largely due to highly sensitive detectors deployed at the Southport endpoint of the cable to reduce environmental - or ‘noise’ - interference. 

Researchers liken this to interference from the sun on a laptop screen - reduce the external light interference and the user can function as normal again. 

Paula Cogan, Chief Executive Officer of euNetworks, said: “We are proud to support a critical project that pushes the boundaries of quantum technology and has implications for the future of network security.  

“The successful integration of quantum technology over commercial-grade optical fibre infrastructure at this distance is an exciting step forward. Rockabill, and the euNetworks’ Super Highway network it is part of, provide the ideal platform for new and progressive technologies that will enhance and innovate future network infrastructure.”

More experiments will need to be carried out using the same cable line to pave the way for integrating the services offered by quantum technologies into standard communications for industries sending private data between the UK and Ireland.

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About this research

The project, funded by the EPSRC Quantum Communications Hub, will be presented at the NATO Symposium on Quantum Technology for Defence and Security conference on 03 October.

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