When two light beams cross paths the photons that make the light cross each other in an uninteresting way, making the concept of lightsabers seem impossible.
But now scientists at MIT and Harvard University have shown that photons can be made to “interact” with each other which is paving the way for quantum computing and Star Wars space weapons.
The leader of the team of scientists working on the research, MIT’s Professor Vladan Vuletic, said: “The interaction of individual photons has been a very long dream for decades.”
The scientists shone a weak laser through a dense cloud of ultra-cold rubidium atoms.
Instead of the photons exiting the cloud as a single, randomly spaced photons, they joined together.
Photos usually have no mass at all and move at the speed of light (300,000km per second).
But the scientists found that the photons bound together at a fraction of the electron’s mass which meant they became more sluggish – travelling at around 100,000 times slower than a normal photon.
The light also remained bound together even after leaving the cloud and had a “memory” when they got out.
Co-author Sergio Cantu said: “What’s neat about this is, when photons go through the medium, anything that happens in the medium, they ‘remember’ when they get out.”
This means the photons that have interacted with each other can be thought of as strongly entangled – a key property for any quantum computing bit.
Professor Vuletic added: “Photons can travel very fast over long distances, and people have been using light to transmit information, such as in optical fibres.
“If photons can influence one another, then if you can entangle these photons, and we’ve done that, you can use them to distribute quantum information in an interesting and useful way.”
The research was published in the journal Science, supported in part by the National Science Foundation.
The team will now look for ways to make other interactions with photons, such as repulsion.
This may involve photons scattering off each other like billiard balls.
Professor Vuletic concluded: “It’s completely novel in the sense that we don’t even know sometimes qualitatively what to expect.
“With repulsion of photons, can they be such that they form a regular pattern, like a crystal of light?
“Or will something else happen? It’s very uncharted territory.”