Researchers have showed that by tweaking a few parameters of the binding process, photons could travel side by side as a sort of "molecule", which could let scientists build objects out of photons in future.
In 2013, collaborators from Harvard, Caltech and Massachusetts Institute of Technology (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 'Star Trek' lightsabers were just around the corner.
Now researchers from National Institute of Standards and Technology (NIST) and University of Maryland, along with other collaborators, 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," said 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," Gorshkov said.
However, Gorshkov said he is not optimistic that building a Jedi Knights' lightsaber would be possible anytime soon.
The main reason is that binding photons requires extreme conditions difficult to produce with a roomful of lab equipment, let alone fit into a sword's handle.
Still, there are plenty of other reasons to make molecular light - humbler than lightsabers, but useful nonetheless, researchers said.
For example, engineers need a way to precisely calibrate light sensors, and Gorshkov said the findings could make it far easier to create a "standard candle" that shines a precise number of photons at a detector.
Perhaps more significant to industry, binding and entangling photons could allow computers to use photons as information processors, a job that electronic switches in your computer do today.
Not only would this provide a new basis for creating computer technology, but it also could result in substantial energy savings.
Phone messages and other data that currently travel as light beams through fibre optic cables has to be converted into electrons for processing - an inefficient step that wastes a great deal of electricity.
If both the transport and the processing of the data could be done with photons directly, it could reduce these energy losses, researchers said.
Gorshkov said it will be important to test the new theory in practice for these and other potential benefits.
The study appears in the journal Physical Review Letters.
