Hey Professor: Mikhail D. Lukin

The chance to channel your inner Obi Wan Kenobi might be closer than you think.
By Kathryn J. Gundersen

The chance to channel your inner Obi Wan Kenobi might be closer than you think. Working within the Harvard Quantum Optics Center and the Harvard-MIT Center for Ultracold Atoms, Harvard professor Mikhail D. Lukin and MIT professor Vladan Vuletic recently led research through which they discovered a new state of matter that behaves similarly to Star Wars lightsabers. Though it’s still in its early stages, the future's looking bright for this new type of light technology.

Fifteen Minutes: How did you come to discover this, and how does it work?

Mikhail D. Lukin: Quantum theory is by now about a hundred years old, with well established basic principles. Right now, though, what we are trying to do is to not just be able to explain it, but to also control quantum systems, all the way down to individual quanta. This in particular involves control of light at the quantum level. But one of the features of the light field is that if you take two light beams, they just go through each other. What this means is the fundamental quanta of light fields, called photons, do not interact with each other. This work basically addresses the problem of trying to make single photons interact with each other; this is important, for example, for applications such as the processing of information, which is carried by light fields. What we have developed allows us to make single photons interact so strongly that they form a molecule.

FM: How is this similar to the famed Star Wars lightsabers?

MDL: Basically, the physics behind our observations is similar to what we see in the movies. We created an optical medium such that if you take two faint light beams, consisting of just single photons, they don’t actually just pass through each other, but the photons inside start interacting with each other, or talking to each other, much like massive material particles. This not unlike what we see in the movies, where eventually the light beams behave almost like solid objects. So this analogy is apparently very fascinating.

FM: What do you think could be in the future for your discovery?

MDL: In the future, there are several directions that we and others are pursuing. One of them is to try to make bigger and more complex objects from photons. The molecules consisting of two photons that we observe can be thought as a kind of new form of matter. We would like to create more complex objects, like,  for example, crystals out of single photons of light. There is also an applied part to this work, because as I mentioned before, photons are the best candidates for carrying information. You can encode information in just one single photon, which makes this transmission perfectly secure: no one can intercept such a message without being detected. What our work does is it shows a way how to actually make the single photons interact with each other, build single photon switches and transistors, and, by that, process the information carried by light fields. And that is one of the frontiers of modern technology, because it can be used in the development of quantum computers and quantum communication systems.