Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quantum physics: On the way to quantum networks

27.01.2020

Physicists at Ludwig-Maximilians-Universitaet (LMU) in Munich, together with colleagues at Saarland University, have successfully demonstrated the transport of an entangled state between an atom and a photon via an optic fiber over a distance of up to 20 km - thus setting a new record.

'Entanglement' describes a very particular type of quantum state which is not attributed to a single particle alone, but which is shared between two different particles. It irrevocably links their subsequent fates together - no matter how far apart they are - which famously led Albert Einstein to call the phenomenon as "spooky action at a distance".


Picture of the single atom trap. In the ultra-high vacuum glass cell a single Rubidium atom is captured, which later will be entangled with a photon.

Photo: C. Olesinski/LMU

Entanglement has become a cornerstone of new technologies based on effects at the quantum level and is distribution over long distances a central goal in quantum communication.

Now LMU researchers led by physicist Harald Weinfurter, in collaboration with a team at the University of the Saarland in Saarbrücken, have shown that the entangled state of an atom and a photon can be transmitted via an optic fiber (like those used in telecommunications networks) over a distance of up to 20 km.

The previous record was 700 meters. "The experiment represents a milestone, insofar as the distance covered confirms that quantum information can be distributed on a large scale with little loss," says Weinfurter. "Our work therefore constitutes a crucial step toward the future realization of quantum networks."

Quantum networks essentially consist of quantum memories (made up of one or more atoms, for example) that act as nodes, and communication channels in which photons (light quanta) can propagate to link the nodes together. In their experiment, the researchers entangled a rubidium atom with a photon, and were able to detect the entangled state - which now shares the quantum properties of both particles - after its passage through a 20-km coil of optic fiber.

The biggest problem the experimenters faced start with the properties of the rubidium atom. Following targeted excitation, these atoms emit photons with a wavelength of 780 nanometers, in the near-infrared region of the spectrum.

"In an optic fiber made of glass, light at this wavelength is rapidly absorbed," Weinfurter explains. Conventional telecommunications networks therefore make use of wavelengths around 1550 nanometers, which markedly reduces losses in transit.

Obviously, this wavelength would also improve the experimenters' chances of success. So Matthias Bock, a member of the group in Saarbrücken, built what is called a quantum frequency converter that was specifically designed to increase the wavelength of the emitted photons from 780 to 1520 nanometers.

This task itself posed a number of extremely demanding technical challenges. For it was imperative to ensure that conversion from only a single photon to only one other photon happens and that none of the other properties of the entangled state, especially the polarization of the photon, were altered during the conversion process. Otherwise, the entangled state would be lost.

"Thanks to the use of this highly efficient converter, we were able to maintain the entangled state over a much longer range at telecommunications wavelengths, and therefore to transport the quantum information that it carries over long distances," says Weinfurter.

In the next step, the researchers plan to frequency convert the light emitted by a second atom, which should enable them to generate entanglement between the two atoms over long telecommunications fibers.

The properties of glass-fiber cables vary depending on factors such as the temperature and strain to which they are exposed. For this reason, the team intends to first carry out this experiment under controlled conditions in the laboratory.

In the event of success, field experiments will be undertaken also adding new nodes to a growing network. After all, even long journeys can be successfully completely by taking one step at a time.

Media Contact

Kathrin Bilgeri
kathrin.bilgeri@lmu.de
089-218-06938

http://www.uni-muenchen.de 

Kathrin Bilgeri | EurekAlert!
Further information:
http://www.en.uni-muenchen.de/news/newsarchiv/2020/weinfurter_entanglement.html
http://dx.doi.org/10.1103/PhysRevLett.124.010510

More articles from Physics and Astronomy:

nachricht K-State study reveals asymmetry in spin directions of galaxies
03.06.2020 | Kansas State University

nachricht The cascade to criticality
03.06.2020 | ETH Zurich Department of Physics

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: K-State study reveals asymmetry in spin directions of galaxies

Research also suggests the early universe could have been spinning

An analysis of more than 200,000 spiral galaxies has revealed unexpected links between spin directions of galaxies, and the structure formed by these links...

Im Focus: New measurement exacerbates old problem

Two prominent X-ray emission lines of highly charged iron have puzzled astrophysicists for decades: their measured and calculated brightness ratios always disagree. This hinders good determinations of plasma temperatures and densities. New, careful high-precision measurements, together with top-level calculations now exclude all hitherto proposed explanations for this discrepancy, and thus deepen the problem.

Hot astrophysical plasmas fill the intergalactic space, and brightly shine in stellar coronae, active galactic nuclei, and supernova remnants. They contain...

Im Focus: Biotechnology: Triggered by light, a novel way to switch on an enzyme

In living cells, enzymes drive biochemical metabolic processes enabling reactions to take place efficiently. It is this very ability which allows them to be used as catalysts in biotechnology, for example to create chemical products such as pharmaceutics. Researchers now identified an enzyme that, when illuminated with blue light, becomes catalytically active and initiates a reaction that was previously unknown in enzymatics. The study was published in "Nature Communications".

Enzymes: they are the central drivers for biochemical metabolic processes in every living cell, enabling reactions to take place efficiently. It is this very...

Im Focus: New double-contrast technique picks up small tumors on MRI

Early detection of tumors is extremely important in treating cancer. A new technique developed by researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from normal tissue. The work is published May 25 in the journal Nature Nanotechnology.

researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from...

Im Focus: I-call - When microimplants communicate with each other / Innovation driver digitization - "Smart Health“

Microelectronics as a key technology enables numerous innovations in the field of intelligent medical technology. The Fraunhofer Institute for Biomedical Engineering IBMT coordinates the BMBF cooperative project "I-call" realizing the first electronic system for ultrasound-based, safe and interference-resistant data transmission between implants in the human body.

When microelectronic systems are used for medical applications, they have to meet high requirements in terms of biocompatibility, reliability, energy...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Dresden Nexus Conference 2020: Same Time, Virtual Format, Registration Opened

19.05.2020 | Event News

Aachen Machine Tool Colloquium AWK'21 will take place on June 10 and 11, 2021

07.04.2020 | Event News

International Coral Reef Symposium in Bremen Postponed by a Year

06.04.2020 | Event News

 
Latest News

An MRI technique has been developed to improve the detection of tumors

03.06.2020 | Medical Engineering

K-State study reveals asymmetry in spin directions of galaxies

03.06.2020 | Physics and Astronomy

The cascade to criticality

03.06.2020 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>