Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ultracold atoms in a "Rydberg-dress"

11.08.2016

Scientists at the MPQ (Garching) and MPIPKS (Dresden) have developed a novel technique to let atoms interact over large distances.

Many properties of our everyday world can be explained if atoms are thought of as small, solid marbles, which feel each other only if brought in direct contact with each other. The temperature of the air surrounding us, for example, is the result of uncountable, continuously occurring collisions between its constituents.


Fig. 1: From the starting state densely filled with atoms (left), a ring-like structure emerges due to the long range interaction (right).

Graphic: MPQ, Quantum Many-Body Systems Division


Fig. 2: The type of interaction can be controlled by light, from angularly independent (left and middle) to angularly dependent interaction (right).

Graphic: MPQ, Quantum Many-Body Systems Division

Contrary to this, we also know effects which arise from the interplay between two distant objects. Well-known examples are two magnets which can affect each other also at quite a distance, or the formation of a salt crystal as a regular arrangement of positively charged sodium and negatively charged chlorine ions, which are bound together at large distances by electrical attraction.

In the microscopic quantum world, such interactions at a distance are of special interest, as on the one hand they are the origin of foundational, well known phenomena such as the formation of ordered crystals. On the other hand they also promise to allow for experimentally studying novel and up to now unknown states of matter. Moreover, such long-range interacting systems are hard to treat theoretically on a fundamental level, attaching special value to experimental studies.

Now, a team of researchers around Dr. Christian Groß and Prof. Immanuel Bloch (MPQ Garching) in collaboration with Dr. Thomas Pohl (MPIPKS Dresden) has developed a novel method to let atoms interact over a large distance (Nature Physics, 1 August 2016). The key element thereby is the so called “Rydberg-dressing”, which makes use of a fundamental property of quantum mechanics, namely the fact that a quantum object can be in a superposition of two states at the same time. To illustrate this phenomenon, one often quotes the famous “Schrödinger’s cat”, devised by the theoretical physicist Erwin Schrödinger, which is held in a closed box in a superposition of the states “dead” and “alive”.

In analogy, in the experiment atoms are brought into a superposition of two states. “The trick consists of choosing a highly excited “Rydberg-state” next to the energetically lowest lying ground state”, explains Johannes Zeiher, doctoral candidate at the experiment. “These exotic states are characterized by a 1000-fold increased diameter. Therefore, Rydberg atoms can influence each other at enormous distances.” The catch, however, is that Rydberg-atoms are unstable and decay within a very short time. The scientists take this hurdle by choosing a very unequal superposition, in which the atoms are in the unstable Rydberg state only with a small probability. “To some extent, each atom only obtains a very thin “Rydberg-dress”, which nevertheless can be experienced by other, distant atoms”, elucidates Christian Groß, leader of the experiment.

In the laboratory, the physicists start the experiment by creating an ultracold gas of the alkali metal rubidium-87 with the aid of the technique of laser-cooling. From this gas, approximately 200 atoms are transferred to a so called optical lattice, a periodic arrangement of microscopic light traps, which are formed by several laser beams. Within a single plane, each of these microscopic traps is dimensioned such that it can hold precisely one atom. The resulting order of the atoms is a well-controlled starting state for the next, decisive step: the implementation of “Rydberg-dressing” by shining in very intense, ultraviolet laser light. In this light-woven “Rydberg-dress”, the atoms started feeling and affecting each other at a distance, similar to two magnets repelling or attracting each other at a much larger scale in our macroscopic world. A crucial difference is, however, that in the microscopic system this interaction can be switched on and off by controlling the ultraviolet light.

To provide the proof for the so generated long range interactions, the experimentalist chose an interferometric technique which allows for an especially sensitive probe of the system. To this end, the “dressed atoms”, for which the ground state is superposed with the Rydberg state, are compared to usual atoms. The mutual attraction or repulsion of the Rydberg atoms leaves characteristic footprints in the interference pattern arising from this comparison. These can be detected by imaging the atoms one by one with the aid of a specialized fluorescence microscope.

A first measurement provided direct evidence that the atoms feel each other at large distances. As a consequence, the behaviour of each atom is also influenced by its neighbours. Figure 1 shows both the initial distribution of about 200 atoms, which homogeneously occupy a disc shaped area, as well as the resulting interference pattern for the atoms in superposition with the Rydberg state. The edge of the system stands out as a ring-like structure, as the atoms there lack their neighbours at the outside.

A deeper analysis of the structures in the interference pattern allowed for a more precise measurement and characterization of the interaction. The experiments confirm with excellent accuracy the theoretical predictions. A particularly interesting feature is the possibility to create angularly dependent interactions (Figure 2). This means that two atoms lying next to each other feel each other differently depending on whether they follow each other from left to right or orthogonal to this direction.

“This phenomenon also can be observed with two magnets, which repel or attract each other with different strength, depending on whether they are arranged next to each other or before each other”, says Christian Groß. Contrary to this, the interaction underlying the crystal formation of sodium and chlorine ions is independent of the angle. Also this more simple type of interaction could be realized in the lab, controlled by the ultraviolet laser (Figure 2).

The research teams around Immanuel Bloch, Christian Groß and Thomas Pohl succeeded in inducing and characterizing a novel form of interaction between two atoms. Control over this interaction with the aid of light opens the path to study microscopic systems, in which atoms act like small magnets and interact over large distances. Such systems promise studies of a large variety of exciting phenomena, for example of the thus far not experimentally observed “Super-solid”, which is a state of matter that is a solid and a fluid at the same time. [JZ/OM]

Original publication:
Johannes Zeiher, Rick van Bijnen, Peter Schauß, Sebastian Hild, Jae-yoon Choi, Thomas Pohl, Immanuel Bloch, and Christian Groß
Many-body interferometry of a Rydberg-dressed spin lattice
Nature Physics, 1. August 2016, DOI: 10.1038/NPHYS3835

Contact:

Dr. Christian Groß
Max Planck Institute of Quantum Optics
Hans-Kopfermann-Str. 1
85748 Garching, Germany
Phone: +49 (0)89 32 905 - 713
E-mail: christian.gross@mpq.mpg.de

Prof. Dr. Immanuel Bloch
Chair of Quantum Optics, LMU Munich
Schellingstr. 4, 80799 Munich
Director at the Max Planck Institute of Quantum Optics
Hans-Kopfermann-Str. 1
85748 Garching, Germany
Phone: +49 (0)89 / 32 905 -138
E-mail: immanuel.bloch@mpq.mpg.de

Dr. Olivia Meyer-Streng
Press & 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 für Quantenoptik
Further information:
http://www.mpq.mpg.de/

More articles from Physics and Astronomy:

nachricht Physicists Design Ultrafocused Pulses
27.07.2017 | Universität Innsbruck

nachricht CCNY physicists master unexplored electron property
26.07.2017 | City College of New York

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: Physicists Design Ultrafocused Pulses

Physicists working with researcher Oriol Romero-Isart devised a new simple scheme to theoretically generate arbitrarily short and focused electromagnetic fields. This new tool could be used for precise sensing and in microscopy.

Microwaves, heat radiation, light and X-radiation are examples for electromagnetic waves. Many applications require to focus the electromagnetic fields to...

Im Focus: Carbon Nanotubes Turn Electrical Current into Light-emitting Quasi-particles

Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers

Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...

Im Focus: Flexible proximity sensor creates smart surfaces

Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.

At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

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

26.07.2017 | Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

 
Latest News

Programming cells with computer-like logic

27.07.2017 | Life Sciences

Identified the component that allows a lethal bacteria to spread resistance to antibiotics

27.07.2017 | Life Sciences

Malaria Already Endemic in the Mediterranean by the Roman Period

27.07.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>