When most people ask me about what I do, I usually answer with the statement, "I study the physics of cold atoms."
If I answer that I study atomic physics (which I do), people tend to associate that with the nuclear physics, i.e., working with the atomic bomb (which I don't). Atomic physics is the study of physics at the energy level of atoms (a few electron-volts at most), not at the level of disassociating the Uranium nucleus, fission, which is at the heart of the atomic bomb (a few hundred Mega electron-volts, 220 MeV).
More specifically, I study the physics of a dilute gas of sodium Bose-Einstein condensates.
What in the world is a Bose-Einstein Condensate?
A Bose-Einstein condensate (BEC, for short) is another phase of a specific type of matter, called bosons, at ultra-cold temperatures (a few micro-degrees above absolute zero).
In principle, the phase transition is similar to that of liquid water turning to solid ice.
As we lower the temperature of the sodium gas in our chamber, it turns from being individual atoms (with dimensions of a few angstroms, 10-10 meters, at room temperature) rattling in our magnetic trap into a giant matter wave of about 10 million cold atoms (with the dimensions of a few tens to hundreds of microns, 10-6 meters, more than 100,000 times larger). The temperature of this phase transtion is around a micro degree above absolute zero, unlike the water-ice transition at 273 degrees K (0 degrees Celsius).
The weirdness of a BEC is that the atoms lose their individuality. All of the atoms share common characteristics, a single quantum-mechanical wavefunction. They become coherent like a laser and have properties of a superfluid.
(Also see What
is a BEC?)
What is it good for?
Well, the answer to this one is somewhat long-winded.
Currently, BECs are an active area of research around the world (See GSU for number places with BECs). They are a curiosity since they show various aspects of classical mechanics in a quantum-mechanical world. They also connect the fields of condensed matter with atomic physics. One can use atomic physics techniques to study condensed matter.
But, one of the most important possible use of a BEC is as an atom laser. Since the atoms in a BEC are coherent they exhibit laser-like properties. So, in principle, one has a very bright coherent source of atoms which can be used for making better atomic clocks, gyroscopes, gravity gradiometers, etc. They may also be used for drawing finer lines, for lithography, although this is a bit unrealistic right now.
However, the thing to keep in mind is that BEC in dilute gases was discovered/invented in 1995, very recently. In the 60s when the light laser was invented, apart from its obvious use as a bright soure of photons, nobody even dreamt that its use would be so widespread today. A light laser is currently used in CD players, supermarket scanners, to cut and weld steel, opthomology, etc., outside of its ubiquitous use in research.
Similarly, the BEC field today is cutting edge research. Scientists all around the world, including our own lab at MIT, are exploring the basic science. Poking and probing its properties will inevitably lead to something. This is not to imply that your local supermarket will carry a atom laser scanner or that you will be listening to a music system made using BECs, but that more research and bright minds are needed. At worst, it is a new toy to play with.
How do we do it?