Quantum memory crystals are a step towards a futuristic internet

A secure quantum internet is one step closer because of a quantum memory created from a crystal, that could form a crucial part of a device able to transmit entangled photons over a distance of 5 kilometres. Crucially, it really is entirely appropriate for existing communication networks, making it suitable for real-world use.

There has always been a vision of a quantum version of the web, which would allow quantum computers to communicate across long distances by exchanging particles of light called photons which may have been linked as well as quantum entanglement, permitting them to transmit quantum states.

The problem is that photons get lost if they are transmitted through long lengths of fibre-optic cable. For normal photons, this isn’t an issue, because networking equipment can merely measure and retransmit them after a particular distance, which is how normal fibre data connections work. But for entangled photons, any try to measure or amplify them changes their state.

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The solution to the is an operation called quantum teleportation. This calls for simultaneously measuring the state of 1 photon from each of two pairs of entangled photons, which effectively links the most distant two photons in the chain.

Read more: Quantum internet: The race is to build an unhackable online world

“The photons are being used not to send the info, but to talk about the entanglement. Then I may use that entanglement. I could teleport the quantum information I want from A to B,” says Myungshik Kim at Imperial College London.

But that introduces another problem – all your entangled pairs need to be ready simultaneously to create a chain, which becomes more difficult over longer distances. To fix this, you desire a quantum memory.

“The idea is that you try one link, so when you have successful, then you stall this entanglement which link and you await the other connect to be also ready. So when the other links are ready, then you can combine them together. This will extend the entanglement towards larger and larger distances,” says Hugues de Riedmatten at the Institute of Photonic Sciences in Castelldefels, Spain.

de Reidmatten and his team used yttrium orthosilicate crystals to store pairs of entangled photons for 25 microseconds in two separate quantum memories. They performed the experiment between two labs, linked by 50 metres of fibre-optic cable, but theoretically this amount of storage time allows devices up to 5 kilometres apart to communicate.

Crucially, the researchers were able to store and retrieve photons in the order these were sent, and transmit them using frequencies and fibre-optic cables already found in data networks, showing that the approach should work outside the lab. They now desire to increase the distance between the two memory devices by increasing the utmost storage time and make a fully functioning quantum repeater.

Journal reference: Nature , DOI: 10.1038/s41586-021-03481-8

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A secure quantum internet is one step closer because of a quantum memory created from a crystal, that could form a crucial part of a device able to transmit entangled photons over a distance of 5 kilometres. Crucially, it really is entirely appropriate for existing communication networks, making it suitable for real-world use. There has…

A secure quantum internet is one step closer because of a quantum memory created from a crystal, that could form a crucial part of a device able to transmit entangled photons over a distance of 5 kilometres. Crucially, it really is entirely appropriate for existing communication networks, making it suitable for real-world use. There has…

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