Physicists build atomic lasers that can stay on forever

Physicists from the University of Amsterdam are building an atomic laser that can stay on forever. Credit: UvA

These days, it is difficult to imagine our everyday life without a laser. Lasers are used in printers, CD players, units of measure, pointers and so on.

What makes lasers so special is that they use continuous light waves: all the light inside a laser vibrates completely synchronized. Meanwhile, quantum mechanics tells us that particles such as atoms should also be considered as waves. As a result, we can build ‘[{” attribute=””>atom lasers’ containing coherent waves of matter. But can we make these matter waves last, so that they may be used in applications?

In research that was published in the journal Nature on June 8, a team of physicists from the University of Amsterdam shows that the answer to this question is affirmative.

Getting bosons to march in sync

The concept that underlies the atom laser is the so-called Bose-Einstein Condensate, or BEC for short.

Elementary particles in nature occur in two types: fermions and bosons. Fermions are particles like electrons and quarks – the building blocks of the matter that we are made of. Bosons are very different in nature: they are not hard like fermions, but soft: for example, they can move through one another without a problem. The best-known example of a boson is the photon, the smallest possible quantity of light.

But matter particles can also combine to form bosons – in fact, entire atoms can behave just like particles of light. What makes bosons so special is that they can all be in the exact same state at the exact same time, or phrased in more technical terms: they can ‘condense’ into a coherent wave. When this type of condensation happens for matter particles, physicists call the resulting substance a Bose-Einstein Condensate.

Coherent Matter Waves

The central part of the experiment in which the coherent matter waves are created. Fresh atoms (blue) fall in and make their way to the Bose-Einstein Condensate in the center. In reality, the atoms are not visible to the naked eye. Image processing by Scixel. Credit: UvA

In everyday life, we are not at all familiar with these condensates. The reason: it is very difficult to get atoms to all behave as one. The culprit destroying the synchronicity is temperature: when a substance heats up, the constituent particles start to jiggle around, and it becomes virtually impossible to get them to behave as one. Only at extremely low temperatures, about a millionth of a degree above