Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quantum diffraction at a breath of nothing

26.08.2015

Physicists build stable diffraction structure in atomically thin graphene

The quantum mechanical wave nature of matter is the basis for a number of modern technologies like high resolution electron microscopy, neutron-based studies on solid state materials or highly sensitive inertial sensors working with atoms. The research in the group around Prof. Markus Arndt at the University of Vienna is focused on how one can extend such technologies to large molecules and cluster.


Modern fabrication methods allow to make atomically thin nanomasks which prove to be sufficiently robust for experiments in molecular quantum optics.

Copyright: Quantennanophysik, Fakultät für Physik, Universität Wien; Bild-Design: Christian Knobloch

In order to demonstrate the quantum mechanical nature of a massive object it has to be delocalized first. This is achieved by virtue of Heisenberg's uncertainty relation: If molecules are emitted from a point-like source, they start to 'forget' their position after a while and delocalize.

If you place a grating into their way, they cannot know, not even in principle, through which slit they are flying. It is as if they traversed several slits at the same time. This results in a characteristic distribution of particles behind the grating, known as the diffraction or interference pattern. It can only be understood if we take the particles' quantum mechanical wave nature into account.

At the technological limit

In a European collaboration (NANOQUESTFIT) together with partners around Professor Ori Cheshnovsky at Tel Aviv University (where all nanomasks were written), as well as with support by groups in Jena (growth of biphenyl membranes, Prof. Turchanin), and Vienna (High-Resolution Electron Microscopy, Prof. Meyer) they now demonstrated for the first time that such gratings can be fabricated even from the thinnest conceivable membranes.

They milled transmission masks into ultra-thin membranes of silicon nitride, biphenyl molecules or carbon with a focussed ion beam and analysed them with ultra-high resolution electron microscopy. The team succeeded in fabricating stable and sufficiently large gratings even in atomically thin single layer graphene.

In previous quantum experiments of the same EU collaboration, the thickness of diffraction masks was already as thin as a hundredth of the diameter of a hair. However, even such structures were still too thick for the diffraction of molecules composed of dozens of atoms.

The same force that allows geckos to climb walls restricts the applicability of material gratings in quantum diffraction experiments: Molecules are attracted to the grating bars like the geckos' toes to the wall. However, once they stick to the surface they are lost to the experiment. A grand challenge was to reduce the material thickness and thus the attractive interactions of these masks down to the ultimate limit while retaining a mechanically stable structure.

"These are the thinnest possible diffraction masks for matter wave optics. And they do their job very well", says Christian Brand, the lead author of this publication. "Given the gratings' thickness of a millionth of a millimetre, the interaction time between the mask and the molecule is roughly a trillion times shorter than a second. We see that this is compatible with high contrast quantum interference".

A thought experiment of Bohr and Einstein

The bars of the nanogratings look resemble the strings of a miniature harp. One may therefore wonder whether the molecules induce vibrations in these strings when they are deflected to the left or the right during quantum diffraction. If this were the case the grating bars could reveal the molecular path through the grating and quantum interference should be destroyed. The experiment thus realizes a thought experiment that was discussed by Nils Bohr and Albert Einstein already decades ago:

They asked whether it is possible to know the path a quantum takes through a double slit while observing its wave nature. The solution to this riddle is again provided by Heisenberg's uncertainty principle: Although the molecules give the grating a little kick in the diffraction process this recoil remains always smaller than the quantum mechanical momentum uncertainty of the grating itself. It therefore remains undetectable. Here it is shown that this applies even to membranes that are only one atom thick.

###

Publication in "Nature Nanotechnology":

"An atomically thin matter-wave beamsplitter"; C. Brand, M. Sclafani, C. Knobloch, Y. Lilach, T. Juffmann, J. Kotakoski, C. Mangler, A. Winter, A. Turchanin, J. Meyer, O. Cheshnovsky, M. Arndt; Nature Nanotechnology (2015),

DOI: 10.1038/nnano.2015.179

The University of Vienna, founded in 1365, is one of the oldest and largest universities in Europe. About 9,500 employees, 6,700 of who are academic employees, work at 19 faculties and centres. This makes the University of Vienna Austria's largest research and education institution. About 92,000 national and international students are currently enrolled at the University of Vienna. With more than 180 degree programmes, the University offers the most diverse range of studies in Austria. The University of Vienna is also a major provider of continuing education. In 2015, the Alma Mater Rudolphina Vindobonensis celebrates its 650th Anniversary. http://www.univie.ac.at

Media Contact

Christian Brand
brandc6@univie.ac.at
43-142-775-1172

 @univienna

http://www.univie.ac.at/en/ 

Christian Brand | EurekAlert!

More articles from Physics and Astronomy:

nachricht First Juno science results supported by University of Leicester's Jupiter 'forecast'
26.05.2017 | University of Leicester

nachricht Measured for the first time: Direction of light waves changed by quantum effect
24.05.2017 | Vienna University of Technology

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 the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>