Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

An infallible quantum measurement

05.08.2013
For quantum physicists, entangling quantum systems is one of their every day tools.

Entanglement is a key resource for upcoming quantum computers and simulators. Now, physicists in Innsbruck/Austria and Geneva/Switzerland realized a new, reliable method to verify entanglement in the laboratory using a minimal number of assumptions about the system and measuring devices. Hence, this method witnesses the presence of useful entanglement.


The new method allows for reliable statements about the entanglement in a system.
Uni Innsbruck/Ritsch

Their findings on this ‘verification without knowledge’ has been published in Nature Physics.

Quantum computation, quantum communication and quantum cryptography often require entanglement. For many of these upcoming quantum technologies, entanglement – this hard to grasp, counter-intuitive aspect in the quantum world – is a key ingredient. Therefore, experimental physicists often need to verify entanglement in their systems. “Two years ago, we managed to verify entanglement between up to 14 ions”, explains Thomas Monz. He works in the group of Rainer Blatt at the Institute for Experimental Physics, University Innsbruck. This team is still holding the world-record for the largest number of entangled particles. “In order to verify the entanglement, we had to make some, experimentally calibrated, assumptions.

However, assumptions, for instance about the number of dimensions of the system or a decent calibration, make any subsequently derived statements vulnerable”, explains Monz. Together with Julio Barreiro, who recently moved on the Max Planck Institute of Quantum Optics in Garching, and Jean-Daniel Bancal from the group of Nicolas Gisin at the University of Geneva, now at the Center for Quantum Technologies in Singapore, the physicists derived and implemented a new method to verify entanglement between several objects.

Finding correlations

The presented device-independent method is based on a single assumption: “We only have to make sure that we always apply the same set of operations on the quantum objects, and that the operations are independent of each other”, explains Julio Barreiro. “However, which operations we apply in detail – this is something we do not need to know.” This approach - called Device Independent - allows them to get around several potential sources of error, and subsequently wrong interpretations of the results.

“In the end, we investigate the correlations between the settings and the obtained results. Once the correlations exceed a certain threshold, we know that the objects are entangled.” For the experimentally hardly avoidable crosstalk of operations applied to levitating calcium ions in the vacuum chamber in Innsbruck, the Swiss theorist Jean-Daniel Bancal managed to adapt the threshold according to a worst-case scenario. “When this higher threshold is breached, we can claim entanglement in the system with high confidence”, states Bancal.

Assumptions as Achilles heel

For physicists, such procedures that are based on very few assumptions are highly interesting. By being basically independent of the system, they provide high confidence and strengthen the results of experimentalists. “Assumptions are always the Achilles heel – be that for lab data or theory work”, stresses Thomas Monz. “We managed to reduce the number of assumption to verify entanglement to a minimum. Our method thus allows for reliable statements about the entanglement in a system.” In the actual implementation, the physicists in Innsbruck could verify entanglement of up to 6 ions. This new method can also be applied for larger systems. The technical demands, however, also increase accordingly.

Publication: Demonstration of genuine multipartite entanglement with device-independent witnesses. Julio T. Barreiro, Jean-Daniel Bancal, Philipp Schindler, Daniel Nigg, Markus Hennrich, Thomas Monz, Nicolas Gisin, and Rainer Blatt. Advance Online Publication, Nature Physics 2013 (DOI: 10.1038/NPHYS2705)

Contact:
Thomas Monz
Institute for Experimental Physics
University of Innsbruck
Telefon: +43 512 507 52452
E-Mail: thomas.monz@uibk.ac.at
Web: http://www.quantumoptics.at/
Jean-Daniel Bancal
Centre of Quantum Technologies
National University of Singapore
Telefon: +65 6516 5626
E-Mail: jdbancal.physics@gmail.com
Christian Flatz
Public Relations
University of Innsbruck
Telefon: +43 512 507 32022
Mobil: +43 676 872532022
E-Mail: christian.flatz@uibk.ac.at
Sylvie Délèze
Attachée de presse
Université de Genève
24, rue Général-Dufour
1211 Genève 4
Tél.: 022 379 73 98
Courriel: sylvie.deleze@unige.ch
Weitere Informationen:
http://dx.doi.org/10.1038/NPHYS2705 - Demonstration of genuine multipartite entanglement with device-independent witnesses. Julio T. Barreiro, Jean-Daniel Bancal, Philipp Schindler, Daniel Nigg, Markus Hennrich, Thomas Monz, Nicolas Gisin, and Rainer Blatt. Advance Online Publication, Nature Physics 2013

Dr. Christian Flatz | Universität Innsbruck
Further information:
http://www.uibk.ac.at
http://www.quantumoptics.at/

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 >>>