2021-11-20

MIT physicists use basic atomic properties to make matter “invisible”

By yqqlm yqqlm

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they found that this effect can inhibit the scattering of light by atomic clouds

MIT physicists use basic atomic properties to make matter “invisible”

generally, when photons penetrate the atomic cloud, photons and atoms can collide with each other like billiards, scattering light in all directions, so as to make the atomic cloud visible. However, the MIT team observed that when atoms were supercooled and super squeezed, the Pauli principle began to work, and particles effectively reduced the space of scattered light. Instead, photons flow and are not scattered

in their experiments, physicists observed this effect in a cluster of lithium atoms. As they become colder and denser, atoms scatter less light and gradually become darker. The researchers suspect that if they can push the conditions further up to absolute zero, the cloud will become completely invisible

the results of the research team reported in the journal Science on Tuesday represent the first observation of the effect of poly blocking on atomic light scattering. This effect was predicted 30 years ago, but it has not been observed until now

Wolfgang Ketterle, Professor of physics at MIT, John D. Arthur, said: “In general, Pauli incompatibility has been proved and is absolutely crucial to the stability of the world around us. What we have observed is a very special and simple form of poly blocking, that is, it prevents an atom from doing what all atoms naturally do: scattering light. This is the first time to clearly observe the existence of this effect, which shows physics A new phenomenon in. ”

MIT physicists use basic atomic properties to make matter “invisible”(1)

when Ketterle came to MIT as a postdoctoral 30 years ago, his mentor David Pritchard, namely Cecil and Ida green physics professors, made a prediction that Pauli incompatibility would inhibit the way some atoms called fermions scattered light.

Broadly speaking, his idea is that if atoms are frozen to near rest and squeezed into a sufficiently narrow space, they will behave like electrons in a dense energy shell. There is no space to change their speed or position. If photons flow in, they cannot scatter.

“An atom can only scatter photons if it can absorb its kick force by moving to another chair,” Ketterle explained, citing the analogy of the arena seat. “If all the other chairs are occupied, it will no longer be able to absorb kick force and scatter photons. Therefore, the atom becomes transparent.”

“This phenomenon has never been observed before because people cannot generate sufficiently cold and dense clouds,” Ketterle added.

in recent years, physicists including Ketterle’s team have developed magnetic and laser based technologies to reduce atoms to ultra-low temperatures. The limiting factor, he said, is density.

“If the density is not high enough, an atom can still scatter light by skipping a few chairs until it finds some space,” Ketterle said. “That’s the bottleneck. ”

MIT physicists use basic atomic properties to make matter “invisible”(2)

in their new research, he and his colleagues used their previously developed technology to first freeze a mass of fermions — in this case, a special lithium atom isotope with three electrons, three protons and three neutrons. They put a mass of lithium protons “Then we used a tightly focused laser to squeeze the ultracold atoms to record the density, which reached about 400 million atoms per cubic centimeter,” the researchers explained

the researchers then irradiated another laser beam into the cloud. They carefully calibrated the laser beam so that its photons do not heat ultracold atoms or change their density as light passes through. Finally, they used a lens and camera to capture and calculate the photons they managed to disperse.

“we are actually calculating hundreds of photons, which is really amazing.” “A photon is such a small amount of light, but our equipment is very sensitive. We can see that they are a small light ball on the camera,” Margalit said

at cooler temperatures and higher densities, atoms scatter less and less light, as predicted by Pritchard’s theory. At their coldest, about 20 microkelvin, atoms darken by 38%, which means that they scatter 38% less light than less cold and lower density atoms.

Margalit said: “This super cold and very dense cloud system has other effects that may deceive us. Therefore, it took us months to screen and put aside these effects to obtain the clearest measurement results.”

now the research team has observed that poly blocking can indeed affect the ability of atoms to scatter light. Ketterle said that this basic knowledge may be used to develop materials that inhibit light scattering, such as storing data of quantum computers.

“Whenever we control the quantum world, such as in a quantum computer, light scattering is a problem, which means that information will leak out of your quantum computer,” he thought. “This is a way to suppress light scattering, and we are contributing to the overall theme of controlling the atomic world.”