Still, it’s a huge advance for so-called “atomic lasers,” beams of atoms traveling in a single wavelength band that could one day be used to test fundamental physical constants and engineer sophisticated techniques. The first atomic laser was created back in 1996 by a team of physicists at MIT. The concept sounds simple: Just as traditional light-based lasers consist of photons moving in synchrony with their waves, lasers made of atoms will need their own wave-like properties to align before becoming a beam of light.
However, as with many things in science, conceptualization is easier than implementation. Atomic lasers have their roots in a state of matter called a Bose-Einstein condensate, or BEC. BECs are created by cooling a clump of bosons to just a fraction of a degree above absolute zero. At such low temperatures, atoms sink to their lowest possible energy state without coming to a complete stop.
When they reach these low energies, the quantum properties of the particles can no longer interfere with each other, and they are so close together that they overlap a bit, creating a dense cloud of atoms that behaves like a “super atom” or matter wave. However, BECs are an oxymoron. They are very fragile; even light can destroy BECs. Given that the atoms in the BEC are cooled with an optical laser, this usually means that the BEC’s existence is short-lived.
The atomic lasers that scientists have managed to achieve so far are pulsed, not continuous, and require only one pulse to be fired before a new BEC needs to be produced. To create a continuous BEC, a team of researchers at the University of Amsterdam in the Netherlands realized something needed to change.
In previous experiments, the gradual cooling of atoms was all done in one place. In this research group setup, they decided to spread out the cooling steps not in time, but in space, allowing the atoms to move as they passed through successive cooling steps, and finally, the ultracold atoms reached the center of the experiment, where they could be Used to form coherent matter waves in BECs. But when these atoms are used, new ones are already on the way to complement the BEC. In this way, they can keep the process going, basically forever.