Physicists say they have made an atomic laser that can work “forever”

A new breakthrough has allowed physicists to create a beam of atoms that behaves in the same way as a laser, and which could theoretically last “forever.”

This could ultimately mean that technology is on the path to practical application, although there are important limitations that still apply.

However, this is a big step forward for what is known as an “atomic laser”: a single wave beam made of atoms that could one day be used to test fundamental physical constants and microengineering technology.

The corn laser a minute ago. The first atomic laser was created by a team of MIT physicists in 1996. The concept seems quite simple: just as traditional light-based lasers consist of photons moving with their synchronized waves, the Lasers made of atoms require their undulating nature to align them before mixing them like a beam.

However, as with many things in science, it is easier to visualize concepts than to perceive them. At the root of the laser atom is a state of matter called the Bose-Einstein BEC capacitor.

The BEC is generated by the cooling of the cloud from the bosons to only a fraction above absolute zero. At such low temperatures, the atoms sink to the lowest possible energy state without stopping completely.

When they reach these low energies, the quantum properties of the particles cannot interfere with each other; They are close enough to each other to cause some kind of interference, resulting in a cloud of high-density atoms that behaves like a single “super atom” or wave of matter.

However, the BECs are somewhat contradictory. It is very fragile. Even light can destroy BEC. Since BEC atoms are cooled by optical laser, this usually means that a BEC is ephemeral.

The atomic laser that scientists have been able to achieve so far has been pulsed, not versatile; It only involves firing a pulse before a new BEC needs to be created.

In order to create a continuous BEC, a team of researchers from the University of Amsterdam in the Netherlands realized that something needed to change.

“In previous experiments, the gradual cooling of the atoms was done in one place. In our configuration, we decided to propagate the cooling steps not over time, but in space: we make the atoms move as they move. which progress through the successive cooling steps, “explained physicist Florian Schreck.

“Finally, the ultra-cold atoms reach the heart of the experiment, where they can be used to form waves of matter consistent with the BEC. But as they use these atoms, the new atoms are already on their way to replacing the BEC. , we can keep the process going, essentially forever. “

This “heart of the experiment” is the trap that protects the BEC from light, a tank that can be filled continuously for the duration of the experiment.

However, protecting the BEC from the light of cooling lasers, while simple in theory, became even more difficult in practice. Not only were there technical hurdles, but also bureaucratic and administrative hurdles.

“When we moved to Amsterdam in 2013, we started with a leap of faith, borrowed money, an empty room, and a fully funded personal grant team,” said physicist Chun Chia-chen, who led the research.

“Six years later, in the early hours of Christmas morning in 2019, the experiment was finally up to the task. We had the idea of ​​adding an additional laser beam to solve one last technical problem, and instantly every The photo we took showed BEC, the first continuous wave BEC. “

Now that the first part of the continuous atom laser, the “continuous atom” part, has been achieved, the team said the next step is to maintain a constant atomic beam. They can achieve this by moving atoms to an unconfined state, thus extracting a wave of diffuse matter.

They said they used strontium atoms, a popular choice for BECs, the chance to open up exciting opportunities. Atomic interferometry with strontium BEC can be used, for example, to do research on relativity and quantum mechanics, or to detect gravitational waves.

“Our experiment is the material wave analog of a continuous-wave optical laser with fully reflective cavity mirrors,” the researchers wrote in their paper.

“This proof-of-principle demonstration provides a new piece of atomic optics that was hitherto lacking, which allows the construction of coherent continuous-wave devices.”

The research was published in a temperate manner.

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