September 10, 2015

NIST Physicists Show ‘Molecules’ Made of Light May Be Possible

Title: Photon Molecule
Description: Researchers show that two photons, depicted in this artist?s conception
as waves (left and right), can be locked together at a short distance. Under certain
conditions the photons can form a state resembling a two-atom molecule,
represented as the blue dumbbell shape at center. Credit: E. Edwards/JQI

(September 10, 2015)  It’s not lightsaber time, not yet. But a team including theoretical physicists from the National Institute of Standards and Technology (NIST) has taken another step toward building objects out of photons, and the findings* hint that weightless particles of light can be joined into a sort of “molecule” with its own peculiar force.

The findings build on previous research that several team members contributed to before joining NIST. In 2013, collaborators from Harvard, Caltech and MIT found a way to bind two photons together so that one would sit right atop the other, superimposed as they travel. Their experimental demonstration was considered a breakthrough, because no one had ever constructed anything by combining individual photons—inspiring some to imagine that real-life lightsabers were just around the corner.

Now, in a paper forthcoming in Physical Review Letters, the NIST and University of Maryland-based team (with other collaborators) has showed theoretically that by tweaking a few parameters of the binding process, photons could travel side by side, a specific distance from each other. The arrangement is akin to the way that two hydrogen atoms sit next to each other in a hydrogen molecule.

“It’s not a molecule per se, but you can imagine it as having a similar kind of structure,” says NIST’s Alexey Gorshkov. “We’re learning how to build complex states of light that, in turn, can be built into more complex objects. This is the first time anyone has shown how to bind two photons a finite distance apart."

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