Scientists from the National Institute of Standards in Technology (NIST) say they’ve created the world’s first molecules made of light. Their work builds on prior research into the possibility of so-called “photonic” matter, advancing from simpler forms to these new, multi-part structures. They say it’s an all new form of matter, previously only theoretical in nature, and they believe it could be the basis for a new approach to light-based technology.
One of the most important principles in the study of light is that photons, the units of light, are massless and they do not interact with one another. To create something like photonic matter, we’d need to be able to keep photons reliably interacting over time, which is classically thought to be impossible.
In 2013, many of these same NIST contributors managed to make single overlapping photon structures by layering them directly on top of one another. The two photons were fired into a cloud of super-cooled rubidium atoms in a sealed chamber, causing the photons to donate a large portion of the energy they carry to the cooled atoms around, and to thus slow significantly. As the second photon enters the cloud that was just excited by the first, it catches up to the first and begins to interact.
What’s important is that the photons are only interacting via the cloud of atoms in the rubidium medium — each photon affects the cloud, which then affects the other photon, which then affects the cloud, and on and on it goes. This leads to a push-pull mechanism that causes the two photons to exit the cloud as one and, more importantly, to stay as one. They perfectly overlap, moving and behaving as a single additive unit.
At the time, the researchers said that this was not unlike the physics of crossed Star Wars lightsabers, in which two light sources are able to physically repel one another. The analogy doesn’t make much sense, really, but it did make the basic point that here we have beams of light physically interacting, as had been previously thought impossible. The process still requires large machinery and “cryogenic” temperatures, rather than a self-made sword hilt with a crystal in it.
This week’s study took that concept a step further by making two-photon “molecules” in which they do not perfectly overlap, but which move in coordinated tandem much like two atoms in a molecule of normal matter. The two-photon structures arise from slight variations in the photon-firing process, emerging and traveling at a stable distance from one another.
The implications for tech could be enormous. Many of our most sensitive technologies are based on light, from communication through fiber-optic cables to micrography and global-scale image capture. The ability to control the behavior of photons in this way could, if made easy enough, let each pulse carry more information than a simple yes or no, on or off — the overall state of a multi-photon structure could then be the signal, and who knows how many differentiable states that might be able to carry?
It’s too early to talk too much about the possible applications, but this is part of a fundamental thread of research into the nature of light, and if it continues far enough, it could change our whole relationship with photons.
