  The future quantum internet will leverage existing communication
infrastructures, including deployed optical fibre networks, to enable novel
applications that outperform current information technology. In this scenario,
we perform a feasibility study of quantum communications over an industrial 224
km submarine optical fibre link deployed between Southport in the United
Kingdom (UK) and Portrane in the Republic of Ireland (IE). With a
characterisation of phase drift, polarisation stability and arrival time of
entangled photons, we demonstrate the suitability of the link to enable
international UK-IE quantum communications for the first time.

Quantum Physics