Researchers discovered that when they fired two protons into the cloud they exited as one molecule.
The explanation of why this happens can be explained by something called the Rydberg blockade. This states that if an atom is excited then nearby atoms can’t be excited to the same degree. And in the case of this experiment the photon travels through the cloud, it then excites an atom, but then it must move forward before the next photon can excite nearby atoms. As this happens the photons push and pull each other as they excite the nearby atoms. This interaction makes the photons act like molecules and when they exit the cloud together they’re much more likely to exit as one instead of two.
However, this discovery doesn’t exactly mean that light sabers will soon be available at your local Hot Topic or Cabela’s. The application has other possibilities though.
“…photons remain the best possible means to carry quantum information. The handicap, though, has been that photons don’t interact with each other.” Lukin says. For example, in building a quantum computer researchers need a means to preserve the quantum information and then be able to process the information with quantum logic operations. However, in order to process this information there needs to be a system that requires the quantum systems to be switched because quantum logic requires the interaction between individual quanta.
This experiment is a proof-of-concept in which a practical quantum switch or photonic logic gate can be constructed.
It may even be able to create three dimensional complex crystals completely out of light. It could even be used in classical computing considering the power-dissipation challenges chip-makers now face.
Lukin says, “what it will be useful for we don’t know yet, but it’s a new state of matter, so we are hopeful that new applications may emerge as we continue to investigate these photonic molecules’ properties.”