Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

'Ultracold' molecules promising for quantum computing, simulation

13.03.2014

Researchers have created a new type of "ultracold" molecule, using lasers to cool atoms nearly to absolute zero and then gluing them together, a technology that might be applied to quantum computing, precise sensors and advanced simulations.

"It sounds counterintuitive, but you can use lasers to take away the kinetic energy, resulting in radical cooling," said Yong P. Chen, an associate professor of physics and electrical and computer engineering at Purdue University.

Physicists are using lasers to achieve such extreme cooling, reducing the temperature to nearly absolute zero, or minus 273 degrees Celsius (minus 459 degrees Fahrenheit) - the lowest temperature possible in the universe.

At these temperatures atoms are brought to a near standstill, making possible new kinds of chemical interactions that are predominantly quantum mechanical in nature. The process is performed inside of an apparatus called a magneto-optical trap, a system that uses a vacuum chamber, magnetic coils and a series of lasers to cool and trap the atoms.

"This is our test tube," said Daniel S. Elliott, a professor of electrical and computer engineering and physics. "In ultracold chemistry, molecules are really moving slowly so they have a long time to interact with each other."

Other researchers have used the method to create cold molecules out of atoms of other alkali metals, which are relatively easy to turn into ultracold molecules. The Purdue researchers are the first to achieve the milestone with the alkali metals lithium and rubidium, in work led by Chen and Elliott.

Findings are detailed in a research paper that appeared as a "Rapid Communication" in the February issue of the journal Physical Review A, a publication of the American Physical Society. The paper was authored by former Purdue physics doctoral student Sourav Dutta, who has graduated; graduate students John Lorenz and Adeel Altaf; Elliott and Chen. The paper is available online at http://pra.aps.org/abstract/PRA/v89/i2/e020702

The method is called photoassociation: two atoms are merged using lasers to induce a chemical bond between them, forming a molecule. These molecules may contain two of the same types of atoms - making them homonuclear - or they can contain two different types of atoms, heteronuclear, such as the case with the lithium-rubidium molecules created by the team.

If the molecules are heteronuclear there is a difference in electric charge between these two atoms and the molecule is said to be polar. This difference in charge is called a dipole moment, which enables interaction between molecules. The greater the dipole moment, the stronger the interaction.

The lithium-rubidium molecule is potentially ideal for various applications, including quantum computing, because it has a significant dipole moment, which can enable these molecules to be used as "quantum bits."

Quantum computers would take advantage of a phenomenon described by quantum theory called "entanglement." Instead of only the states of one and zero used in conventional computer processing, there are many possible "entangled quantum states" in between one and zero, dramatically increasing the capacity to process information.

"In quantum computing the larger the dipole moment the stronger the interaction would be between molecules, and you need that interaction," Elliott said. "They need to interact with each other in order to affect each other, the key to entanglement."

Another potential advantage for the lithium-rubidium molecule is that it can be produced in large quantities.

"The rate of production is much greater for lithium-rubidium than for other bi-alkali-metal molecules," Chen said. "That was a pleasant surprise. It was already known that it has the third- largest dipole moment among bi-alkali-metal molecules, but nobody expected it would be made so efficiently."

Ultracold means temperatures less than about one thousandth of degree above absolute zero. Achieving such frigid extremes requires reducing the kinetic energy of molecules as well as their "internal excitation energies," which are stored in three ways: the rotation of the molecule itself, the vibrations of the atomic nuclei, and the movement of electrons in "shells" surrounding the nuclei. The combined energy of the trio is called rovibronic, a shortened version of rotational, vibrational and electronic.

"We are reporting a highly efficient production of ultracold lithium-rubidium molecules by photoassociation," Dutta said. "This provides the first step towards the production of such ultracold lithium-rubidium molecules in their ground, polar state."

Molecules in their "ground state" have the lowest possible rovibronic energy, which would make them more stable and easier to control.

A related research paper was also published by the team in January in the journal Europhysics Letters, a publication of the European Physical Society. That paper is available online at http://iopscience.iop.org/0295-5075/104/6/63001/article

"Lithium rubidium is one of the last bi-alkali molecules to be made cold, and we are the first to do this," Chen said. "People knew virtually nothing about these molecules."

Ultimately, researchers are seeking more efficient methods for the production of ultracold molecules.

The research has been funded by Purdue's Bilsland Dissertation Fellowship, the National Science Foundation, Army Research Office, and more recently by a research incentive grant from Purdue's Office of Vice President for Research.

The research falls within a field called AMO, for atomic, molecular, and optical physics, an area under expansion at Purdue.

"AMO physics is an exciting area in the landscape of experimental and theoretical physics," Elliott said. "Seven years ago we had one person working in this area."

Since then, the department has added three faculty members working in AMO and is in the process of adding more.

"Purdue is positioned to become a leader in AMO physics," Chen said. 

Writer: Emil Venere, 765-494-4709, venere@purdue.edu 

Sources: Yong Chen, 765-494-0947, yongchen@purdue.edu

Daniel S. Elliott, 765-494-3442, elliottd@ecn.purdue.edu 

ABSTRACT

Photoassociation of ultracold LiRb∗ molecules: Observation of high efficiency  and unitarity-limited rate saturation

Sourav Dutta,1 , * John Lorenz,1 Adeel Altaf,1 , D. S. Elliott,1, 2 and Yong P. Chen 1, 2

1 Department of Physics, Purdue University

2 School of Electrical and Computer Engineering, Purdue University

We report the production of ultracold heteronuclear 7 Li85 Rb molecules in excited electronic states by photoassociation (PA) of ultracold 7 Li and 85 Rb atoms. PA is performed in a dual-species 7 Li-85 Rb magneto-optical trap (MOT) and the PA resonances are detected using trap loss spectroscopy. We identify several strong PA resonances below the Li (2s 2 S1/2) + Rb (5p 2 P3/2) asymptote and experimentally determine the long range C6 dispersion coefficients. We find a molecule formation rate (PLiRb) of 3.5 × 10 7 s−1 and a PA rate coefficient (KPA) of 1.3 × 10−10 cm3 /s, the highest among heteronuclear bi-alkali-metal molecules. At large PA laser intensity we observe the saturation of the PA rate coefficient (KPA) close to the theoretical value at the unitarity limit. 

Emil Venere | EurekAlert!

More articles from Physics and Astronomy:

nachricht Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst

nachricht Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center

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: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>