In a first, physicists spot elusive ‘free-range’ atoms — confirming a century-old theory about quantum mechanics

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In a first, physicists spot elusive ‘free-range’ atoms — confirming a century-old theory about quantum mechanics

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An illustration of atoms floating freely in the air. | Credit: Stanislaw Pytel via Getty Images

For the first time, scientists have observed solo atoms floating freely and interacting in space. The discovery helps to confirm some of the most basic principles of

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that were first predicted more than a century ago but were never directly verified.

Individual atoms are notoriously difficult to observe due to their quantum nature. Researchers cannot, for example, know both an atom’s position and its velocity at the same time, due to quantum weirdness. But using certain laser techniques, they have captured

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“It’s like seeing a cloud in the sky, but not the individual water molecules that make up the cloud,”

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, a physicist at MIT and co-author of the new research, said in a

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The new method goes one step further, allowing scientists to capture images of “free-range” atoms in free space. First, Zwierlein and his colleagues corralled a cloud of sodium atoms in a loose trap at ultracold temperatures. Then, they shot a lattice of laser light through the cloud to temporarily freeze the atoms in place. A second, fluorescent laser then illuminated the individual atoms’ positions.

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The observed atoms belong to a group called bosons. These particles share the same quantum mechanical state and, as a result, behave like a wave, bunching together. This concept was first

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in 1924 and has subsequently become known as a “de Broglie wave.”

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Top: Two illustrations show how atoms in an atom trap (red) are suddenly frozen in place via an optical lattice. Bottom: Three microscope images show (left to right) bosonic 23Na forming a Bose-Einstein condensate; a single spin state in a weakly interacting 6Li Fermi mixture; and both spin states of a strongly interacting Fermi mixture, directly revealing pair formation. | Credit: Yao et al.

Sure enough, the bosons Zwierlein and his team observed displayed de Broglie wave behavior. The researchers also captured images of lithium fermions — a type of particle that repels similar particles rather than bunching together.

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The results were published May 5 in the journal

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. Two other groups reported using a similar technique to observe pairs of bosons and fermions in the same issue of the journal.

“We are able to see single atoms in these interesting clouds of atoms and what they are doing in relation to each other, which is beautiful,” Zwierlein said.

In the future, the team plans to use the new technique — called “atom-resolved microscopy” — to investigate other quantum mechanical phenomena. For example, they may use it to try observing the “quantum Hall effect,” in which electrons sync up under the influence of a strong magnetic field.

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#physicists #spot #elusive #freerange #atoms #confirming #centuryold #theory #quantum #mechanics

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