Sunday, February 21, 2021

An electrical trigger fires single, identical photons

Secure telecommunications networks and rapid information processing make much of modern life possible. To provide more secure, faster, and higher-performance information sharing than is currently possible, scientists and engineers are designing next-generation devices that harness the rules of quantum physics. Those designs rely on single photons to encode and transmit information across quantum networks and between quantum chips. 

However, tools for generating single photons do not yet offer the precision and stability required for quantum information technology.Researchers have found a way to generate single, identical photons on demand. By positioning a metallic probe over a designated point in a common 2-D semiconductor material, the team led by researchers at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) has triggered a photon emission electrically. The photon's properties may be simply adjusted by changing the applied voltage.

"The demonstration of electrically driven single-photon emission at a precise point constitutes a big step in the quest for integrable quantum technologies," said Alex Weber-Bargioni, a staff scientist at Berkeley Lab's Molecular Foundry who led the project. The research is part of the Center for Novel Pathways to Quantum Coherence in Materials (NPQC), an Energy Frontier Research Center sponsored by the Department of Energy, whose overarching goal is to find new approaches to protect and control quantum memory that can provide new insights into novel materials and designs for quantum computing technology.

Photons are one of the most robust carriers of quantum information and can travel long distances without losing their memory, or so-called coherence. To date, most established schemes for secure communication transfer that will power large-scale quantum communications require light sources to generate one photon at a time. Each photon must have a precisely defined wavelength and orientation. The new photon emitter demonstrated at Berkeley Lab achieves that control and precision. It could be used for transferring information between quantum processors on different chips, and ultimately scaled up to larger processors and a future quantum internet that links sophisticated computers around the world.

The photon emitter is based on a common 2-D semiconductor material (tungsten disulfide, WS2), which has a sulfur atom removed from its crystal structure. That carefully located atomic imperfection, or defect, serves as a point where the photon can be generated through application of an electric current.

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