Quantum chaos in ultracold gas discovered

March 12, 2014
Even simple systems, such as neutral atoms, can possess chaotic behavior. Credit: Erbium Team, University of Innsbruck

A team of University of Innsbruck researchers discovered that even simple systems, such as neutral atoms, can possess chaotic behavior, which can be revealed using the tools of quantum mechanics. The ground-breaking research, published in the journal Nature, opens up new avenues to observe the interaction between quantum particles.

The team of Francesca Ferlaino, Institute for Experimental Physics of the University of Innsbruck, Austria, has experimentally shown chaotic behavior of particles in a quantum gas. "For the first time we have been able to observe quantum chaos in the scattering behavior of ," says an excited Ferlaino. The physicists used random matrix theory to confirm their results, thus asserting the universal character of this statistical theory. Nobel laureate Eugene Wigner formulated random matrix theory to describe complex systems in the 1950s. Although interactions between neutrons with atomic nuclei were not well-known then, Wigner was able to reliably predict properties of complex spectra by using random matrices. Today random matrix theory is applied broadly not only in physics but also in number theory, wireless information technology and risk management models in finance to name only a few fields of application. In the Bohigas-Giannoni-Schmit conjecture random matrix theory has been connected to in quantum mechanical systems. Catalan physicist Oriol Bohigas, who passed away last year, can be considered the father of quantum chaos research.

Chaos in the quantum world

To observe quantum chaos, the physicists in Innsbruck cool erbium atoms to a few hundred nanokelvin and load them in an optical dipole trap composed of laser beams. They then influence the scattering behavior of the particles by using a . After holding the atoms in the trap for 400 milliseconds, the researchers record the atom number remaining in the trap. Thus, the scientists are able to determine at which magnetic field two atoms are coupled to form a weakly-bound molecule. At this magnetic field, so-called Fano-Feshbach resonances emerge. After varying the magnetic field in each experimental cycle and repeating the experiment 14,000 times, the physicists identified 200 resonances.

This is experimental physicist Francesca Ferlaino, University of Innsbruck. Credit: University of Innsbruck

"We were fascinated by how many resonances of this type we found. This is unprecedented in the physics of ultracold quantum gases," says Francesca Ferlaino's team member Albert Frisch. To explain the high density of resonances, the researchers used statistical methods. By using Wigner's the scientists are able to show that different molecular levels are coupled. This has also been confirmed by computer simulations conducted by Svetlana Kotochigova's research group at Temple University in Philadelphia, Pennsylvania, USA. "The particular properties of erbium cause a highly complex coupling behavior between the particles, which can be described as chaotic," explains Ferlaino. Erbium is relatively heavy and highly magnetic, which leads to anisotropic interaction between atoms. "The electron shell of these atoms do not resemble spherical shells but are highly deformed," explains Albert Frisch. "Therefore, the type of interaction between two erbium atoms is significantly different from other quantum gases that have been investigated so far."

Studying chaos experimentally

In contrast to everyday speech, chaos does not mean disorder for the physicists but rather a well-ordered system that, due to its complexity, shows random behavior. Ferlaino is excited about their breakthrough: "We have created an experiment that provides a controlled environment to study chaotic processes. We cannot characterize the behavior of single in our experiment. However, by using statistical methods, we can describe the behavior of all particles." She compares the method with sociology, which studies the behavior of a bigger community of people, whereas psychology describes the relations between individuals. This work also provides new inroads to the investigation of ultracold gases and, thus, ultracold chemistry." Ferlaino is convinced: "Our work represents a turning point in the world of ultracold gases."

Explore further: First Bose-Einstein condensate of erbium produced

More information: Quantum Chaos in Ultracold Collisions of Erbium. Frisch A, Mark M, Aikawa K, and Ferlaino F, Bohn JL, Makrides C, Petrov A, and Kotochigova S. Nature 2014 DOI: 10.1038/nature13137 . Available on arXiv:1312.1972v1, http://arxiv.org/abs/1312.1972v1]

Related Stories

First Bose-Einstein condensate of erbium produced

May 22, 2012

Francesca Ferlaino’s research team at the University of Innsbruck is the first to successfully create a condensate of the exotic element erbium. The Innsbruck experimental physicists hold the world record in attaining ...

An icy gaze into the Big Bang

March 18, 2011

(PhysOrg.com) -- Scientists of the Institute for Quantum Optics and Quantum Information (IQOQI) in Innsbruck, Austria, have reached a milestone in the exploration of quantum gas mixtures. In an international first, the research ...

New method to generate Laughlin states with atomic systems

July 3, 2013

In 1998, the Nobel Prize in Physics was conferred to the discovery of a new type of quantum fluid with fractional charge excitations, known as Laughlin state. The production of this quantum state, which explains the behaviour ...

Recommended for you

Two teams independently test Tomonaga–Luttinger theory

October 20, 2017

(Phys.org)—Two teams of researchers working independently of one another have found ways to test aspects of the Tomonaga–Luttinger theory that describes interacting quantum particles in 1-D ensembles in a Tomonaga–Luttinger ...

Using optical chaos to control the momentum of light

October 19, 2017

Integrated photonic circuits, which rely on light rather than electrons to move information, promise to revolutionize communications, sensing and data processing. But controlling and moving light poses serious challenges. ...

Black butterfly wings offer a model for better solar cells

October 19, 2017

(Phys.org)—A team of researchers with California Institute of Technology and the Karlsruh Institute of Technology has improved the efficiency of thin film solar cells by mimicking the architecture of rose butterfly wings. ...

Terahertz spectroscopy goes nano

October 19, 2017

Brown University researchers have demonstrated a way to bring a powerful form of spectroscopy—a technique used to study a wide variety of materials—into the nano-world.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.