This may finally mean that the technology is on its way to practical application, although significant limitations still apply.
Nevertheless, this is a huge step forward in what is known as the “atomic laser” – a beam made of atoms marching like a single wave that could one day be used to test fundamental physical constants and engineering precision technology.
Atomic lasers have been around for a minute. The first atomic laser was created by a team of physicists at the Massachusetts Institute of Technology in 1996. The concept sounds quite simple: just as a traditional light-based laser consists of photons moving with their waves in sync, a laser made of atoms will require own wave -like nature to align before being stirred like a ray.
However, as with many things in science, it is easier to conceptualize than to realize. At the heart of the atomic laser is a state of matter called Bose-Einstein condensate or BEC.
BEC is created by cooling a cloud of bosons to just one part above absolute zero. At such low temperatures, atoms sink to the lowest possible energy state without stopping completely.
When they reach these low energies, the quantum properties of the particles can no longer interfere with each other; they move close enough to each other to overlap, resulting in a high-density cloud of atoms that behaves like a “super atom” or a wave of matter.
However, BECs are something of a paradox. They are very fragile; even light can destroy BEC. Given that the atoms in BEC are cooled by optical lasers, this usually means that the existence of BEC is fleeting.
The atomic lasers that scientists have been able to achieve so far have been of the pulsed rather than the continuous variety; and involve firing only one pulse before a new BEC must be generated.
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 atoms was done in one place. In our setup, we decided to distribute the cooling steps not in time but in space: we make the atoms move as they go through successive cooling steps,” explained physicist Florian. Shrek.
“Eventually, ultra-cold atoms arrive at the heart of the experiment, where they can be used to form coherent materials in BEC. But while these atoms are being used, the new atoms are about to fill the BEC. that way we can continue the process – essentially forever. “
This “heart of the experiment” is a trap that keeps the BEC protected from light, a tank that can be refilled continuously while the experiment continues.
However, protecting the BEC from the light produced by the cooling laser, although simple in theory, was again a little more difficult in practice. There were not only technical obstacles, but also bureaucratic and administrative ones.
“When we moved to Amsterdam in 2013, we started with a jump in faith, borrowed money, an empty room and a team fully funded by personal subsidies,” said physicist Chun-Chia Chen, who led the study.
“Six years later, in the early hours of Christmas morning 2019, the experiment was finally on the edge of work. We had the idea to add an extra laser beam to solve the latest technical difficulties and immediately every image we took showed BEC, the first continuous wave BEC. “
Now that the first part of the continuous atomic laser has been realized – the “continuous atom” part – the next step, the team said, is working to maintain a stable atomic beam. They could achieve this by transferring the atoms to an uncaptured state, thus extracting a wave of propagating matter.
Because they used strontium atoms, a popular choice for the BEC, the prospect opens up exciting opportunities, they said. Atomic interferometry using strontium BEC, for example, can be used to study relativity and quantum mechanics or to detect gravitational waves.
“Our experiment is analogous to the matter of a continuous-wave optical laser with fully reflective mirror cavities,” the researchers wrote in their paper.
“This demonstration to prove the principle provides a new, hitherto missing part of atomic optics, allowing the construction of continuous devices with coherent matter and waves.
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