Inside Quantum Technology

A New Twist on Quantum Communication in Fiber May Allow Legacy Networks to Be Used

( research done at the University of the Witwatersrand in Johannesburg, South Africa, and Huazhang University of Science and Technology in Wuhan, China, has exciting implications for secure data transfer across optical fiber networks. The team have demonstrated that multiple quantum patterns of twisted light can be transmitted across a conventional fiber link that, paradoxically, supports only one pattern. The implication is a new approach to realizing a future quantum network, harnessing multiple dimensions of entangled quantum light.
The team demonstrated transfer of multi-dimensional entanglement states over 250 m of single-mode fiber, showing that an infinite number of two-dimensional subspaces could be realized. Each subspace could be used for sending information, or multiplexing information to multiple receivers.
“A consequence of this new approach is that the entire high-dimensional OAM Hilbert space can be accessed, but two dimensions at a time. In some sense it is a compromise between simple 2-D approaches and true high-dimensional approaches,” says Forbes. Importantly, high-dimensional states are unsuitable for transmission over conventional fiber networks, whereas this new approach allows legacy networks to be used.

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