Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quantum many-body systems on the way back to equilibrium

23.02.2015

Advances in experimental and theoretical physics enable a deeper understanding of the dynamics and properties of quantum many-body systems

Considering that one cubic centimetre of matter already contains about 10 to the 19 to 10 to the 23 particles it is hard to imagine that physicists nowadays can prepare ensembles comprising only some hundred, or even just a handful of atoms. What is more, they have improved their techniques to the extent that they can manipulate such particles individually or jointly and can fine tune their interactions.


Illustration of the various options to influence the properties of quantum many-body systems.

(Theory Division, MPQ)

Driven by on new numerical techniques, powerful supercomputers, and new mathematical techniques the theoretical description of such systems has seen equally impressive progress. In a recent review article in Nature Physics (3rd of February 2015) the team of Prof. Dr. Jens Eisert, Mathis Friesdorf (both from the Dahlem Center for Complex Quantum Systems, Freie Universität Berlin) and Dr. Christian Gogolin, postdoctoral researcher in the Theory Division of Prof. Ignacio Cirac at MPQ (Garching) and research fellow at ICFO (Barcelona), discuss the various quantum systems that have been realised and how they are described theoretically, and give an outlook on promising developments.

Particularly important in the quest for a better understanding of quantum many-body systems are the processes that take place while a system is on its way back to equilibrium after being perturbed externally. Here the challenge is to bridge the gap between the microscopic description of the local dynamics and the well-known macroscopic description in terms of statistical ensembles. Which picture applies depends crucially on the size of the system and the kind of interaction between the particles.

In many experiments systems with short range interactions are realised. Particularly fruitful have been techniques based on ultracold atomic gases in so-called optical lattices – essentially grids of standing waves generated by counterpropagating laser beams. Such systems can for example be used as models for ferromagnetic materials.

A very interesting aspect of condensed matter physics which can also be investigated with such systems is transport – for example that of electrons and thereby electric charges in crystals. In close collaboration experimentalists and theorists thereby find out which parameters determine properties such as the conductivity, and how defects and disorder influence the mobility of particles.

Large quantum many-body systems are often tackled with statistical methods from thermodynamics. Of particular interest is here the temporal evolution when global parameters – such as temperature or an external field – are changed. Such a change can be sudden or can occur more slowly over extended amounts of time, or even happen periodically. The scientists thereby investigate whether, how, and on what time scales systems go to a new equilibrium state.

In many systems "critical" values for the parameters exist at which a sudden transition to a new "phase" with drastically different properties can be observed – analogous to the melting of ice above zero degree Celsius. Understanding the dynamics of such phase transitions is an ongoing challenge for theoreticians.

Such quantum many-body systems have also proven useful as simulators of large and possibly multi-dimensional lattice systems whose non-equilibrium dynamics is not accessible with analytical or numerical tools. Experimental realisations of such systems can thus be regarded as analogue simulators with which these restrictions can be overcome.

Despite the tremendous progress many questions are still open. Some of the riddles of the tendency to evolve back into equilibrium are now understood, but the question of what defines the time scales on which these relaxation processes happen is still pretty much open. Moreover in the future scientists want to investigate not only closed systems, but also those in which interactions with the environment causes decoherence and dissipation. Such, usually harmful and unwanted processes – if carefully engineered – can be used to prepare interesting phases of matter. [OM/CG]

Original publication:
J. Eisert, M. Friesdorf and C. Gogolin
Quantum many-body systems out of equilibrium
Nature Physics, 3 February 2015, DOI:10.1038/Nphys3215

Contact:

Prof. Dr. Ignacio Cirac
Honorary Professor, TU München
Director at the Max Planck Institute of Quantum Optics
Hans-Kopfermann-Str. 1, 85748 Garching, Germany
Phone: +49 (0)89 / 32 905 -705/-736
Fax: +49 (0)89 / 32 905 -336
E-mail: ignacio.cirac@mpq.mpg.de

Dr. Christian Gogolin
ICFO - The Institute of Photonic Sciences
Mediterranean Technology Park,
Av. Carl Friedrich Gauss, 3,
08860 Castelldefels (Barcelona), Spanien
Phone: +34 935 54 22 37
E-mail: christian.gogolin@icfo.es

Dr. Olivia Meyer-Streng
Press & Public Relations
Max Planck Institute of Quantum Optics, Garching, Germany
Phone: +49 (0)89 / 32 905 -213
E-Mail: olivia.meyer-streng@mpq.mpg.de

Dr. Olivia Meyer-Streng | Max-Planck-Institut für Quantenoptik
Further information:
http://www.mpq.mpg.de/

Further reports about: Max Planck Institute Nature Physics QUANTUM Quantenoptik equilibrium

More articles from Physics and Astronomy:

nachricht A 100-year-old physics problem has been solved at EPFL
23.06.2017 | Ecole Polytechnique Fédérale de Lausanne

nachricht Quantum thermometer or optical refrigerator?
23.06.2017 | National Institute of Standards and Technology (NIST)

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: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>