Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A New Order in the Quantum World

02.11.2012
By using laser beams MPQ scientists generate quantum matter with novel, crystal-like properties.

Both high-valued diamond and low-prized graphite consist of exactly the same carbon atoms. The subtle but nevertheless important difference between the two materials is the geometrical configuration of their building blocks, with large consequences for their properties.


Figure 1: Illustration of an ordering of five Rydberg-atoms. Green: atoms in the ground state. Red: Rydberg-atoms. Violet: Sphere of influence of the Rydberg-atoms
(MPQ, Quantum Many-Body Systems Division)


Figure 2: Different geometrical configurations of selected excitation states: a) Single snapshots of excitations states with a different number of Rydberg-atoms, b) Resulting patterns after grouping many individual images according to the number of Rydberg-atoms, c) Results of the numerical calculations
(MPQ, Quantum Many-Body Systems Division)

There is no way any kind of material could be diamond and graphite at the same time. However, this limitation does not hold for quantum matter, as a team of the Quantum Many-Body Physics Division of Prof. Immanuel Bloch (Max-Planck-Institute of Quantum Optics and Ludwig-Maximilians-Universität München) was now able to demonstrate in experiments with ultracold quantum gases.

Under the influence of laser beams single atoms would arrange to clear geometrical structures (Nature, November 1st, 2012). But in contrast to classical crystals all possible configurations would exist at the same time, similar to the situation of Schrödinger’s cat which is in a superposition state of both “dead” and “alive”. The observation was made after transferring the particles to a highly excited so-called Rydberg-state.

“Our experiment demonstrates the potential of Rydberg gases to realise exotic states of matter, thereby laying the basis for quantum simulations of, for example, quantum magnets,” Professor Immanuel Bloch points out. The experimental work was supported by theoretical model calculations performed in the group of Dr. Thomas Pohl (Max Planck Institute for the Physics of Complex Systems, Dresden).

The experiment begins with cooling an ensemble of a couple of hundred rubidium atoms down to temperatures near absolute zero and catching the atoms in a light trap. The atomic cloud is then superimposed with a periodic light field – a so-called optical lattice which provides an almost uniform filling in the central region of the trap. In the next step laser light is applied to transfer the atoms into a Rydberg-state in which the outermost shell electron is located at a huge distance from the atomic nucleus. As a result, the sphere of influence of these atoms is blown up, like a balloon, by a factor of about 10 000, reaching a comparatively “huge” diameter of several micrometres – about the size of a tenth of the diameter of an average hair. These super-atoms now interact strongly via so-called van der Waals forces, which act over a long range.

For the Rydberg states chosen in the experiment, the interaction between the atoms is strongly repulsive, such that the atoms have to keep a minimum distance of several micrometers from each other. This mutual blockade leads to spatial correlations between the atoms such that, depending on the number of Rydberg-atoms, states with different geometrical configurations can emerge (see fig. 1). “However, we have to be aware that in our excited quantum system all geometrical orders are present at the same time. To be precise, all the excitation states form a coherent superposition,” Dr. Marc Cheneau says, a scientist at the experiment. “This new state of matter is a very fragile, crystal-like formation; it exists as long as the excitation is sustained, and fades away once the beam is switched off.”

As soon as the system undergoes an observation the superposition collapses into a specific geometric configuration of Rydberg-atoms, in analogy to the famous example of Schrödinger’s cat which is found, once it is observed, either dead or alive. In a series of “snap shots” of such configurations the scientists revealed the different patterns of the individual excitation states. This is possible by using a special technique which images each Rydberg-atom directly with very high spatial resolution. “We observe the emergence of spatially ordered excitation patterns with random orientation, but a well defined geometry,” Peter Schauß explains, who works at the experiment as a doctoral candidate. In order to recognize the fundamental structures the individual images are grouped according to the number of Rydberg-atoms. Typical microscopic configurations are shown in figure 2. Three atoms are arranged on an equilateral triangle, four or five atoms form quadratic or pentagonal configurations. The experimental data was in good agreement with numerical simulations of the many-body dynamics which were performed by the group of Dr. Thomas Pohl.

As far as the pattern of each individual excitation state is concerned the observations can be described classically. “In order to reveal the quantum physical behaviour of our system we investigated the time-dependent probabilities for the different excitation states, each characterized by a certain number of Rydberg-atoms,” Peter Schauß says “Thereby we were able to discover that the dynamic of the excitation process is ten times as fast as in classical systems without blockade effects. This is a first indication that our system is indeed in a coherent quantum state, composed of different spatially ordered configurations.”

A future challenge for the scientists is the deterministic preparation of Rydberg crystals with a well defined number of excitations. Combining the blockade effect with the single-atom addressing one could engineer quantum gates which can serve as an experimental toolbox for a variety of quantum simulations. Several Rydberg-atoms could be connected to a scalable quantum system for quantum information processing. [Olivia Meyer-Streng]

Original publication:
Peter Schauß, Marc Cheneau, Manuel Endres, Takeshi Fukuhara, Sebastian Hild, Ahmed Omran, Thomas Pohl, Christian Groß, Stefan Kuhr, and Immanuel Bloch
Observation of spatially ordered structures in a two-dimensional Rydberg gas
Nature, November 1st, 2012
Contact:
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 (0) 89 / 32 905 -138
E-mail: immanuel.bloch@mpq.mpg.de
Dr. Marc Cheneau
Max-Planck-Institute of Quantum Optics
Hans-Kopfermann-Straße 1
85748 Garching b. München
Phone: +49 (0) 89 / 32 905 -631
E-mail: marc.cheneau@mpq.mpg.de
Peter Schauß
Max-Planck-Institute of Quantum Optics
Hans-Kopfermann-Straße 1
85748 Garching b. München
Phone: +49 (0) 89 / 32 905 -218
E-mail: peter.schauss@mpq.mpg.de
Dr. Olivia Meyer-Streng
Press and Public Relations
Max-Planck-Institute of Quantum Optics
Phone: +49 (0) 89 / 32 905 -213
E-mail: olivia.meyer-streng@mpq.mpg.de

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

More articles from Physics and Astronomy:

nachricht Heating quantum matter: A novel view on topology
22.08.2017 | Université libre de Bruxelles

nachricht Engineering team images tiny quasicrystals as they form
18.08.2017 | Cornell University

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: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Cholesterol-lowering drugs may fight infectious disease

22.08.2017 | Health and Medicine

Meter-sized single-crystal graphene growth becomes possible

22.08.2017 | Materials Sciences

Repairing damaged hearts with self-healing heart cells

22.08.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>