Conventional Optical Fibre Showing Promise in Use For Quantum Internet

Could legacy fibre networks host the global quantum Internet?

Excerpts and salient points ~

+  Researchers have transmitted multidimensional entangled photons across a record-breaking 250 metres of conventional single-mode optical fibre. This result from a team based in South Africa and China suggests that conventional or “legacy” fibre networks could be used as conduits for secure quantum optical communications, bringing the global quantum Internet a step closer to reality.

By changing the interactions between the photon’s spin and its motion (its spin-orbit coupling), the researchers say they were able to read out all the OAM patterns produced, with each pattern representing a different entangled state. They also demonstrated that they could transfer the multidimensional entangled states across 250 m of single-mode fibre with high fidelity.

+  In previous studies, the maximum reported transmission distance for multidimensional entangled photons was limited to less than one metre. Even then, the researchers had to use a specially-designed custom multimode fibre, rather than the ordinary single-mode fibres that make up the modern global communications network.

+  Researchers led by Jian Wang of Huazhong University of Science and Technology and Andrew Forbes of the University of the Witwatersrand say that they may have overcome this limitation. In their set-up, they entangle the polarization and the OAM of a photon pair, then pass one of the paired photons down an ordinary single-mode fibre while using the other photon to measure OAM patterns. The researchers did this using a holographic technique in which spatial light modulators (SLMs) display patterns that collapse the photon into a given state so it can be measured.

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Source:  physics world.  Belle Dume,  Could legacy fibre networks host the global quantum Internet?

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