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Breakthrough in storage of quantum information taken by University of Cambridge and UT Sydney in Australia

An important step towards much more powerful and secure computer networks and the quantum internet has been taken.

A two-dimensional material that could be used to store quantum information at room temperature has been identified by researchers at the University of Cambridge’s Cavendish Laboratory, working with colleagues from UT Sydney in Australia.

A stock image of a laser on an optic table in a quantum laboratory
A stock image of a laser on an optic table in a quantum laboratory

Quantum memory is a key challenge in building the quantum internet, in which photons are used to store and send information.

The researchers have found that hexagonal boron nitride is capable of emitting single photons from atomic-scale defects in its structure at room temperature.

Light emitted from these isolated defects gives information about a quantum property that can be used to store quantum information, known as spin.

The quantum spin can be accessed via light and at room temperature, which means it could support scalable quantum networks built from two-dimensional materials.

More secure global communication technologies will be enabled by the ability to use photons to send messages.

And the principles of quantum mechanics are beginning to enable far more powerful computers, but to make networks possible, reliable methods of generating single, indistinguishable photons as carriers of information across them are required.

“We can send information from one place to another using photons, but if we’re going to build real quantum networks, we need to send information, store it and send it somewhere else,” said Dr Hannah Stern from Cambridge’s Cavendish Laboratory, co-first author of the study published in Nature Communications, along with Qiushi Gu and Dr John Jarman.

“We need materials that can hold onto quantum information for a certain amount of time at room temperature, but most current material platforms we’ve got are challenging to make and only work well at low temperatures.”

Hexagonal boron nitride is cheap and scalable, and grown by chemical vapour deposition in large reactors.

Dr Stern, a junior research fellow at Trinity College, said: “Usually, it’s a pretty boring material that’s normally used as an insulator. But we found that there are defects in this material that can emit single photons, which means it could be used in quantum systems. If we can get it to store quantum information in spin, then it’s a scalable platform.”

Dr Stern and her colleagues set up a hexagon boron nitride sample near a tiny gold antenna and a magnet of set strength.

They fired a laser at the sample at room temperature to observe magnetic field-dependent responses on the light being emitted from the material. They found that when they shone the laser on the material, they were able to manipulate the spin, or inherent angular momentum, of the defects, and use the defects as a way of storing quantum information.

Co-first author Qiushi Gu said: “Typically, the signal is always the same in these systems, but in this case, the signal changes depending on the particular defect we’re studying, and not all defects show a signal, so there is a lot to still discover.

“There’s a lot of variation across the material, like a blanket draped over a moving surface – you see lots of ripples, and they’re all different.”

Prof Mete Atature, a fellow of St John’s College, who supervised the work, added: “Now that we have identified optically accessible isolated spins at room temperature in this material, the next steps will be to understand their photophysics in detail and explore the operation regimes for possible applications including information storage and quantum sensing. There will be a stream of fun physics following this work.”

The research was supported in part by the European Research Council.

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