Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

JILA researchers make coldest quantum gas of molecules

22.02.2019

JILA researchers have made a long-lived, record-cold gas of molecules that follow the wave patterns of quantum mechanics instead of the strictly particle nature of ordinary classical physics. The creation of this gas boosts the odds for advances in fields such as designer chemistry and quantum computing.

As featured on the cover of the Feb. 22 issue of Science, the team produced a gas of potassium-rubidium (KRb) molecules at temperatures as low as 50 nanokelvin (nK). That's 50 billionths of a Kelvin, or just a smidge above absolute zero, the lowest theoretically possible temperature. The molecules are in the lowest-possible energy states, making up what is known as a degenerate Fermi gas.


Artist's impression of JILA's record-cold quantum gas of potassium-rubidium molecules.

Credit: Steven Burrows/JILA

In a quantum gas, all of the molecules' properties are restricted to specific values, or quantized, like rungs on a ladder or notes on a musical scale. Chilling the gas to the lowest temperatures gives researchers maximum control over the molecules.

The two atoms involved are in different classes: Potassium is a fermion (with an odd number of subatomic components called protons and neutrons) and rubidium is a boson (with an even number of subatomic components). The resulting molecules have a Fermi character.

JILA is jointly operated by the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder. NIST researchers at JILA have been working for years to understand and control ultracold molecules, which are more complex than atoms because they not only have many internal energy levels but also rotate and vibrate. The JILA team made their first molecular gas 10 years ago.

"The basic techniques for making the gas are the same ones we've used before, but we have a few new tricks such as significantly improving the cooling of the atoms, creating more of them in the lowest-energy state," NIST/JILA Fellow Jun Ye said. "This results in a higher conversion efficiency so we get more molecules."

The JILA team produced 100,000 molecules at 250 nK and as many as 25,000 molecules at 50 nK.

Before now, the coldest two-atom molecules were produced in maximum numbers of tens of thousands and at temperatures no lower than a few hundred nanoKelvin. JILA's latest gas temperature record is much lower than (about one-third of) the level where quantum effects start to take over from classical effects, and the molecules last for a few seconds--remarkable longevity, Ye said.

The new gas is the first to get cold and dense enough for the matter waves of these molecules to be longer than distances between them, making them overlap with each other to create a new entity. Scientists call this quantum degeneracy. (Quantum matter can behave as either particles or matter waves, that is, waveform patterns of the probability of a particle's location).

Quantum degeneracy also means an increase in the repulsion among fermionic particles, which tend to be loners anyway, resulting in fewer chemical reactions and a more stable gas. This is the first experiment in which scientists have observed collective quantum effects directly affecting the chemistry of individual molecules, Ye said.

"This is the first quantum degenerate gas of stable molecules in bulk, and the chemical reactions are suppressed--a result that nobody had predicted," Ye said.

The molecules created in this experiment are called polar molecules because they have a positive electric charge at the rubidium atom and a negative charge at the potassium atom. Their interactions vary by direction and can be controlled with electric fields. Polar molecules thus offer more tunable, stronger interactions and additional control "knobs" compared with neutral particles.

These new ultralow temperatures will enable researchers to compare chemical reactions in quantum versus classical environments and study how electric fields affect the polar interactions. Eventual practical benefits could include new chemical processes, new methods for quantum computing using charged molecules as quantum bits, and new precision measurement tools such as molecular clocks.

The process for making the molecules begins with a gas mixture of very cold potassium and rubidium atoms confined by a laser beam. By sweeping a precisely tuned magnetic field across the atoms, scientists create large, weakly bound molecules containing one atom of each type. This technique was pioneered by Ye's colleague, the late Deborah Jin, in her 2003 demonstration of the world's first Fermi condensate.

To convert these relatively fluffy molecules into tightly bound molecules without heating the gas, scientists use two lasers operating at different frequencies--each resonating with a different energy jump in the molecules--to convert the binding energy into light instead of heat. The molecules absorb near-infrared laser light and release red light. In the process, 90 percent of the molecules are converted through an intermediate energy state, to the lowest and most stable energy level.

###

The research is supported by NIST, the Air Force Office of Scientific Research, the Army Research Office and the National Science Foundation.

Paper: L. De Marco, G. Valtolina, K. Matsuda, W.G. Tobias, J.P. Covey and J. Ye. 2018. A Fermi Degenerate Gas of Polar Molecules. Science. Feb 22, 2019 issue. DOI: 10.1126/science.aau7230

Laura Ost | EurekAlert!

Further reports about: Fermi NIST QUANTUM chemical reactions electric charge potassium quantum effects reactions waves

More articles from Physics and Astronomy:

nachricht Heat flow through single molecules detected
19.07.2019 | Okinawa Institute of Science and Technology (OIST) Graduate University

nachricht Better thermal conductivity by adjusting the arrangement of atoms
19.07.2019 | Universität Basel

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Better thermal conductivity by adjusting the arrangement of atoms

Adjusting the thermal conductivity of materials is one of the challenges nanoscience is currently facing. Together with colleagues from the Netherlands and Spain, researchers from the University of Basel have shown that the atomic vibrations that determine heat generation in nanowires can be controlled through the arrangement of atoms alone. The scientists will publish the results shortly in the journal Nano Letters.

In the electronics and computer industry, components are becoming ever smaller and more powerful. However, there are problems with the heat generation. It is...

Im Focus: First-ever visualizations of electrical gating effects on electronic structure

Scientists have visualised the electronic structure in a microelectronic device for the first time, opening up opportunities for finely-tuned high performance electronic devices.

Physicists from the University of Warwick and the University of Washington have developed a technique to measure the energy and momentum of electrons in...

Im Focus: Megakaryocytes act as „bouncers“ restraining cell migration in the bone marrow

Scientists at the University Würzburg and University Hospital of Würzburg found that megakaryocytes act as “bouncers” and thus modulate bone marrow niche properties and cell migration dynamics. The study was published in July in the Journal “Haematologica”.

Hematopoiesis is the process of forming blood cells, which occurs predominantly in the bone marrow. The bone marrow produces all types of blood cells: red...

Im Focus: Artificial neural network resolves puzzles from condensed matter physics: Which is the perfect quantum theory?

For some phenomena in quantum many-body physics several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University in the United States has now successfully deployed artificial neural networks for image analysis of quantum systems.

Is that a dog or a cat? Such a classification is a prime example of machine learning: artificial neural networks can be trained to analyze images by looking...

Im Focus: Extremely hard yet metallically conductive: Bayreuth researchers develop novel material with high-tech prospects

An international research group led by scientists from the University of Bayreuth has produced a previously unknown material: Rhenium nitride pernitride. Thanks to combining properties that were previously considered incompatible, it looks set to become highly attractive for technological applications. Indeed, it is a super-hard metallic conductor that can withstand extremely high pressures like a diamond. A process now developed in Bayreuth opens up the possibility of producing rhenium nitride pernitride and other technologically interesting materials in sufficiently large quantity for their properties characterisation. The new findings are presented in "Nature Communications".

The possibility of finding a compound that was metallically conductive, super-hard, and ultra-incompressible was long considered unlikely in science. It was...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on UV LED Technologies & Applications – ICULTA 2020 | Call for Abstracts

24.06.2019 | Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

 
Latest News

Heat flow through single molecules detected

19.07.2019 | Physics and Astronomy

Heat transport through single molecules

19.07.2019 | Physics and Astronomy

Welcome Committee for Comets

19.07.2019 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>