Laser Cooling Explained: The Nobel Prize-Winning Method

• What is laser cooling? [Overview]:
It is a method of using a laser to lower the temperature of a gas to near absolute zero. See below for details.

• What is the purpose and background of laser cooling?:
Scientists at that time (20th century) wanted to realize Bose-Einstein condensate. Bose-Einstein condensate is a phenomenon in which many particles, called “Bose particles,” behave as waves of the same shape at near absolute zero temperature.

In addition to that, it was also necessary to make it cryogenic in order to realize superconductivity and superfluidity.

• What is laser cooling? [Details]:
As mentioned above, laser cooling aims to reduce the temperature of a gas. First of all, what is temperature? Microscopically speaking, it is the intensity of the motion of the particles that make up the gas. The more intense the movement, the higher the temperature. And the calmer the motion, the lower the temperature. Therefore, “lowering the temperature” is equivalent to “stopping the motion of the particles that make up the gas as much as possible.”

So, how can we stop the motion as much as possible? As you can tell from the name “laser cooling,” it involves irradiating the particles with a laser. In the following, we will consider the cooling of atoms in particular.