Why Ultracold Atoms?
The world that is familiar to us can be described by classical physics. We can predict how far a baseball will fly when you throw it, and we can calculate how long it will take to hit the ground if we drop the ball from a second story window. We can answer questions like "Why sky is blue?", or why a rainbow has all those beautiful colors. Classical physics can explain this macroscopic world beautifully.
When the temperature goes down to a millionth of a degree kelvin, (by the way, outer space is about 3 kelvins), the world that we know, becomes very interesting and quirky. An object that behaves like a particle at room temperature would behave like a wave! The world that we describe things with wave-like properties is called quantum physics.
We study the behavior of atoms in this low temperature regime (we call it the "ultracold" regime) to learn how things work in this microscopic quantum world.
How we do it
We cool atoms using the laser cooling and trapping technique. You might wonder, "Isn't a laser beam hot? Wouldn't it heat things up?". Yes, this does happen (e.g., laser cutting), but when using lasers in just the right way, we can actually cool atoms. You could think of this way: Imagine that the atom is like a bowling bowl and that your laser is made up of tiny particles of light like pingpong balls. As the bowling ball comes towards you, you throw lots of pingpong balls at it, eventually bringing the bowling bowl to a stop. By slowing the atoms down, you are actually cooling them. Temperature is just a measure of the atoms motion.
This method of laser cooling was developed by our advisor Dr. William Phillips, along with Dr. Steven Chu, and Dr. Claude Cohen-Tannoudji, who shared the Nobel Prize in Physics in 1997 for their work. To do this, we need to build several lasers to cool and image the atoms, and then confine them in a magneto-optical trap (MOT).