A new laser cooler technique has helped a team of researchers stop a trapped, rotating molecule in its tracks.
Making molecules behave a certain way can be difficult, but Northwestern University scientists have discovered an "elegant" way to stop a molecule so other applications can be harnessed, according to a press release issued by the university.
"It's counterintuitive that the molecule gets colder, not hotter when we shine intense laser light on it," said lead researchers Brian Odom, an assistant professor of physics and astronomy in the Weinberg College of Arts and Sciences, according to the release. "We modify the spectrum of a broadband laser, such that nearly all the rotational energy is removed from the illuminated molecules. We are the first to stop molecular tumbling in such a powerful yet simple way."
A number of different molecules are easy to capture and hold in place, but they insist on rotating as if they weren't trapped. By using the laser, the researchers were able to cool singly charged aluminum monohydride molecules from room temperature to four degrees Kelvin in just a fraction of a second.
The temperature change caused the molecules to stop rotating, according to the release.
Being able to control a molecule's rotation is important in the construction of superfast quantum computers, which are a lot faster and more powerful than modern computers.
Previously, researchers believed that it would take a ridiculous amount of lasers to stop a molecule's rotation using the cooling method. The scientists made a laser using different components of broadband light to try solving this issue, according to the release.
The team was able to filter out parts of the spectrum that causes the molecules to spin faster and get hotter while leaving in the parts that slow them down and cool them off.
"In our quantum world, every type of motion has only certain allowed energies," Odom said. "If I want to slow down a molecule, quantum mechanics tells me that it happens in steps. And there is a very lowest step that we can get the molecule down to, which is what we've done."
The researchers used aluminum monohydride molecules since they don't vibrate when interacting with a laser. They are also not expensive and could be used for other applications besides quantum computing like "ultracold quantum-controlled chemistry and tests of whether fundamental constants are truly static or if they vary in time."
"There is a lot you can do if you get one species of molecule under control, such as we've done in this study," Odom said.
Findings were published this week in the journal Nature Communications.
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