Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > A Microscopic View on Quantum Fluctuations: Scientists at the Max Planck Institute of Quantum Optics achieve direct imaging of quantum fluctuations at absolute zero temperature

Schematic view of the atom distribution in the optical lattice. Quantum fluctuations (white) are directly visible as neighbouring dark spots.
Credit: Max Planck Institute of Quantum Optics
Schematic view of the atom distribution in the optical lattice. Quantum fluctuations (white) are directly visible as neighbouring dark spots.

Credit: Max Planck Institute of Quantum Optics

Abstract:
Fluctuations are fundamental to many physical phenomena in our everyday life, such as the phase transitions from a liquid into a gas or from a solid into a liquid. But even at absolute zero temperature, where all motion in the classical world is frozen out, special quantum mechanical fluctuations prevail that can drive the transition between two quantum phases. Now a team around Immanuel Bloch and Stefan Kuhr at the Max Planck Institute of Quantum Optics (MPQ) has succeeded in directly observing such quantum fluctuations (Science, 14 October 2011, DOI: 10.1126/science.1209284). Using a high resolution microscope, they were able to image quantum-correlated particle-hole pairs in a gas of ultracold atoms. This allowed the physicists to unravel a hidden order in the crystal and to characterize the different phases of the quantum gas. The work was performed together with scientists from the Theory Division at the MPQ and ETH Zurich. These measurements open new ways to characterize novel quantum phases of matter.

A Microscopic View on Quantum Fluctuations: Scientists at the Max Planck Institute of Quantum Optics achieve direct imaging of quantum fluctuations at absolute zero temperature

Garching, Germany | Posted on October 17th, 2011

The scientists start by cooling a small cloud of rubidium atoms down to a temperature near absolute zero, about minus 273 degree Celsius. The ensemble is then subjected to a light field that severely restricts the motion of the particles along one-dimensional tubes of light aligned in parallel. An additional standing laser wave along the tubes creates a one-dimensional optical lattice that holds the atoms in a periodic array of bright and dark regions of light.

The atoms move in the periodic light field like electrons in solids. As these can be electric conductors or insulators, also the one-dimensional quantum gases can behave like a superfluid or like an insulator at low temperatures. In particular, the height of the optical lattice potential plays an important role: it determines whether the atom is fixed on a particular lattice site or whether it is able to move to a neighbouring site. At very large lattice depths, each lattice site is occupied by exactly one atom. This highly ordered state is called a "Mott insulator", after the British physicist and Nobel laureate Sir Neville Mott. When the lattice depth is decreased slightly, the atoms have enough energy to reach a neighbouring site by quantum mechanical tunneling. In this way, pairs of empty and doubly occupied sites emerge, so-called particle-hole pairs. Intriguingly, these quantum fluctuations also occur at absolute zero temperature, when all movement in the classical world is frozen out. The position of the quantum-correlated particle-hole pairs in the crystal is completely undetermined and is fixed only by the measurement process.

In recent experiments, the physicists around Stefan Kuhr and Immanuel Bloch had already developed a method, which allowed to image single atoms lattice site by lattice site. The atoms are cooled using laser beams, and the fluorescence photons emitted in this process are used to observe the atoms with a high resolution microscope. Holes naturally show up as dark spots, but so do doubly occupied sites as the two particles kick each other out of the lattice in the experiment. Therefore particle-hole pairs appear as two neighbouring dark lattice sites (see figure below). "With our technique, we can directly observe this fundamental quantum phenomenon for the first time", describes doctoral student Manuel Endres enthusiastically.

The physicists measure the number of neighbouring particle-hole pairs through a correlation function. With increasing kinetic energy, more and more particles tunnel to neighbouring sites and the pair correlations increase. However, when the number of particle-hole pairs is very large, it becomes difficult to unambiguously identify them. Hence the correlation function takes on smaller values. Finally, the ordered state of a Mott insulator vanishes completely und the quantum gas becomes a superfluid. Here fluctuations of holes and particles occur independently. The correlation function measured in the experiment is very well reproduced by model calculations, which were performed by scientists from the Theory Division at the MPQ and the ETH Zurich. Interestingly, the same investigations on two-dimensional quantum-gases clearly showed that quantum fluctuations are not as prominent as in one-dimensional systems.

The scientists extended their analysis to correlations between several lattice sites along a string. Such non-local correlation functions contain important information about the underlying many-body system and can be used as an order parameter to characterize different quantum phases. In the experiment described here, such non-local order parameters have been measured for the first time. In the future, the scientists plan to use these measurements for the detection of topological quantum phases. These can be useful for robust quantum computers and could help to understand superconductivity at high temperatures. Olivia Meyer-Streng

Original Publication:

M. Endres, M. Cheneau, T. Fukuhara, C. Weitenberg, P. Schauß, C. Groß, L. Mazza,

M.C. Banuls, L. Pollet, I. Bloch, and S. Kuhr

Observation of Correlated Particle-Hole Pairs and String Order in Low-Dimensional Mott Insulators

Science, 14 October 2011, DOI: 10.1126/science.1209284

####

For more information, please click here

Contacts:
Prof. Dr. Immanuel Bloch

Chair of Quantum Optics

LMU Munich, Schellingstr. 4

80799 München, Germany, and

Max Planck Institute of Quantum Optics

Hans-Kopfermann-Straße 1

85748 Garching b. München

Phone: +49 89 32905 138

e-mail:



Prof. Dr. Stefan Kuhr

University of Strathclyde

Department of Physics

107 Rottenrow East

Glasgow G4 0NG, U.K.

Phone: +44 141-548-3364

e-mail:



Manuel Endres

Max Planck Institute of Quantum Optics

Hans-Kopfermann-Straße 1

85748 Garching b. München

Phone: +49 89 32905 214

e-mail:



Dr. Olivia Meyer-Streng

Press & Public Relations

Max Planck Institute of Quantum Optics

Phone: +49 (0) 89 / 32905 - 213

e-mail:

Copyright © Max Planck Institute of Quantum Optics

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication July 13th, 2018

UMBC researchers develop nanoparticles to reduce internal bleeding caused by blast trauma July 13th, 2018

Leti and Oscaro Partner on Leti’s New Low-Power, Low-Cost Transceiver to Track Parcels July 12th, 2018

Oxford Instruments’ 22 Tesla superconducting magnet system commissioned at the UAM, making it the most intense magnetic field available outside a large international facility July 12th, 2018

Nanometrics to Announce Second Quarter Financial Results on July 31, 2018 July 12th, 2018

Imaging

Oxford Instruments’ 22 Tesla superconducting magnet system commissioned at the UAM, making it the most intense magnetic field available outside a large international facility July 12th, 2018

Alzheimer's breakthrough: Brain metals that may drive disease progression revealed: In brains affected by Alzheimer's, researchers identify chemically reduced iron species, with mineral forms including a magnetic iron oxide June 22nd, 2018

Laboratories

Carbon is the new black: Researchers use carbon nanotubes to develop clothing that can double as batteries July 10th, 2018

NIST Researchers Simulate Simple Logic for Nanofluidic Computing June 30th, 2018

Cleaning or Etching Items with Unique Geometries Requires Specialized Expertise June 27th, 2018

Physics

A refined magnetic sense: Algorithms and hardware developed in the context of quantum computation are shown to be useful for quantum-enhanced sensing of magnetic fields July 2nd, 2018

Discoveries

Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication July 13th, 2018

UMBC researchers develop nanoparticles to reduce internal bleeding caused by blast trauma July 13th, 2018

Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides July 13th, 2018

Researchers identify cost-cutting option in treating nail fungus with nanotechnology: GW researcher Adam Friedman, M.D., studied the potential use of nitric oxide-releasing nanoparticles to improve onychomycosis treatment July 11th, 2018

Announcements

Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication July 13th, 2018

UMBC researchers develop nanoparticles to reduce internal bleeding caused by blast trauma July 13th, 2018

Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides July 13th, 2018

Leti and Oscaro Partner on Leti’s New Low-Power, Low-Cost Transceiver to Track Parcels July 12th, 2018

Quantum nanoscience

Carbon nanotube optics poised to provide pathway to optical-based quantum cryptography and quantum computing: Researchers are exploring enhanced potential of carbon nanotubes for unique applications June 18th, 2018

Making quantum puddles: Physicists discover how to create the thinnest liquid films ever June 13th, 2018

Detecting the birth and death of a phonon June 7th, 2018

Quantum Interference May Be Key to Smaller Insulators: Breakthrough could jumpstart further miniaturization of transistors June 6th, 2018

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project