Scientists at Los Alamos National Laboratory in New Mexico have developed a thin film that can control the release of photons and could have applications in quantum computing.

Made from tungsten and selenium, the two-dimensional material was synthesised using chemical vapour deposition with a multi-step, diffusion-mediated gas source. It can facilitate the emission of single photons of light, a capability essential for all-optical quantum computing and key distribution. Key distribution is a fundamental component of the high-level cybersecurity that quantum technologies promise.  

“Efficiently controlling certain thin-film materials so they emit single photons at precise locations—what’s known as deterministic quantum emission—paves the way for beyond-lab-scale quantum materials,” said Michael Pettes, a Los Alamos National Laboratory materials scientist and leader of the multi-institution research team.

Described in the journal Applied Physics Letters, the research exploits strain at highly spatially localised and well-separated emission sites, or tips, in the tungsten/selenium film. The material’s ultra-thin profile means it conforms to the radius of the tips and bends slightly towards the substrate by a few per cent, like draping a sheet across a bed of nails. The resulting strain is enough to change the electronic structure at the tips, with the affected area emitting light of a different colour and nature than light from the rest of the film.

“While more research is needed to fully understand the role of mechanical deformation in creating these quantum emission sites, we may enable a route to control quantum optical properties by using strain,” Pettes said. “These single-photon sources form the basis for photonics-based, all-optical quantum computing schemes.”

According to the researchers, engineering of quantum emission in 2D materials is still in a very early stage. While studies have observed single photons originating from defect structures in these materials, previous work has suggested that non-uniform strain fields might govern the effect. However, the mechanism responsible for this emergent phenomenon remains unclear and is the focus of ongoing work at Los Alamos.

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