Prototype device enables photon-photon interactions at room temperature for quantum computing

A micrograph of the MIT researchers’ new device, with a visualization of electrical-energy measurements and a schematic of the device layout superimposed on it. Credit: Massachusetts Institute of Technology

Ordinarily, light particles—photons—don’t interact. If two photons collide in a vacuum, they simply pass through each other.

An efficient way to make photons interact could open new prospects for both classical optics and , an experimental technology that promises large speedups on some types of calculations.

In recent years, physicists have enabled photon-photon interactions using atoms of rare elements cooled to very low temperatures.

But in the latest issue of Physical Review Letters, MIT researchers describe a new technique for enabling photon-photon interactions at room temperature, using a silicon crystal with distinctive patterns etched into it. In physics jargon, the crystal introduces “nonlinearities” into the transmission of an optical signal.

“All of these approaches that had atoms or atom-like particles require low temperatures and work over a narrow frequency band,” says Dirk Englund, an associate professor of electrical engineering and computer science at MIT and senior author on the new paper. “It’s been a holy grail to come up with methods to realize single-photon-level nonlinearities at room temperature under ambient conditions.”

Joining Englund on the paper are Hyeongrak Choi, a graduate student in electrical engineering and computer science, and Mikkel Heuck, who was a postdoc in Englund’s lab when the work was done and is now at the Technical University of Denmark.

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