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Rice-Sized Laser, Powered One Electron at a Time, Bodes Well For Quantum Computing


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A battery forces electrons to tunnel one by one through two double quantum dots located at each end of a cavity (above), moving from a higher energy level to a lower energy level and in the process giving off microwaves that build into a coherent beam of light.

Credit: Jason Petta/Department of Physics/Princeton University

Princeton University researchers have developed a rice grain-sized laser powered by single electrons tunneling through artificial atoms known as quantum dots, a breakthrough they say could lead to the creation of quantum computers built out of semiconductor materials.

Quantum dots can communicate through the entanglement of photons, so the researchers designed dots that emit photons when single electrons leap from a higher energy level to a lower energy level to cross the double dot. The researchers fabricated the double quantum dots from extremely thin nanowires made of a semiconductor material called indium arsenide. To construct the new device, they placed the two double dots about six millimeters apart in a cavity made of niobium, which requires a temperature near absolute zero to superconduct.

"This is the first time that the team at Princeton has demonstrated that there is a connection between two double quantum dots separated by nearly a centimeter, a substantial distance," says University of Maryland-National Institute of Standards and Technology professor Jacob Taylor, who collaborated on the research.

The device enables energy levels within the dots to be fine-tuned to generate light at other frequencies. "The double quantum dot allows them full control over the motion of even a single electron, and in return they show how the coherent microwave field is created and amplified," says Princeton professor Claire Gmachl.

From Princeton University
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