Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Single photons produced electrically

16.08.2012
Physicists have succeeded in using semiconductor nanostructures to produce single photons electrically and transfer them via a quantum channel. The application of these single photon sources is seen as further progress toward broader use in secure data communication.

For data transmission over the Internet, electrical computer signals are converted into light signals and conducted via fiber optic cables to the recipient.


This structure produced at the University of Würzburg using semiconductor material with integrated quantum dot nanostructures emits single photons.

Image: Institute of Physics, University of Würzburg

Once there, they are converted back into electrical signals. These light signals can be tapped into on the cables, enabling unauthorized persons to intercept data without detection. However, this does not go undetected if single light particles, photons, are used for encryption based on quantum cryptography.

With this type of encryption, every single photon is polarized individually in a sequence of light particles – vertically, horizontally, or diagonally. Generally speaking, the type of polarization cannot be captured by a third party without changing it as a result. So, the sender and the recipient would notice immediately if an unauthorized person “eavesdropped” on their data transfer and tried to copy the original state of the light particle.

Lasers as single photon sources have disadvantages

The quantum cryptography technique that is currently applied uses greatly weakened lasers as single photon sources. Even though use of this technique has already begun, there are still considerable disadvantages. “With a weakened laser light single photons are released at completely random times, which means that sometimes several photons are also discharged simultaneously,” explains Sven Höfling from the Institute of Physics at the University of Würzburg.

This could then be exploited by hackers to extract information from the data flow without detection. Consequently, in quantum communication with weakened lasers, complex data transmission procedures have to be adopted to guarantee secure communication.

On the other hand, according to Höfling, an ideal single photon source only ever releases a photon when it is triggered by, for example, an electrical pulse. Physicists from the universities of Würzburg, Munich, and Stuttgart have now succeeded in applying such a single photon source in quantum communication.
Publication in the New Journal of Physics

The scientists are presenting their findings in the New Journal of Physics. One of the keys to their success was the close collaboration between the teams led by Professor Harald Weinfurter in Munich, Professor Peter Michler in Stuttgart, and Professors Martin Kamp and Alfred Forchel in Würzburg.

For their single photon sources, the researchers integrated nanostructures made of semiconductor material into microresonators. These sources are highly likely to emit a single photon with every electrical pulse. By implanting information into the polarization of photons, a key can be produced using quantum cryptography, as the researchers demonstrated in their laboratory experiments.

Quantum communication over longer distances

Of course, the scientists are fully aware that the transmission of photons has to work not just in the laboratory, but also over far greater distances. They have already performed successful work aimed at achieving this in a project funded by the Federal Ministry of Education and Research (BMBF). Within this project, they managed to realize secure quantum communication with electrically powered single photon sources over a free-space test distance of around 500 meters over rooftops in the center of Munich.

However, the scientists from Würzburg, Munich, and Stuttgart want to achieve transmission distances that are far greater than this. They are therefore currently researching building blocks for so-called quantum repeaters as part of a group funded by the BMBF involving other research teams. These are analogous to signal amplifiers in traditional communication technology and are essential for long-distance quantum communication.

“Quantum key distribution using quantum dot single-photon emitting diodes in the red and near infrared spectral range”, Tobias Heindel et al, New Journal of Physics, 2 August 2012, doi:10.1088/1367-2630/14/8/083001

Contact

Dr. Sven Höfling, Institute of Physics at the University of Würzburg, T +49 (0)931 31-83613, sven.hoefling@physik.uni-wuerzburg.de

Robert Emmerich | Uni Würzburg
Further information:
http://www.uni-wuerzburg.de

More articles from Physics and Astronomy:

nachricht Structured light and nanomaterials open new ways to tailor light at the nanoscale
23.04.2018 | Academy of Finland

nachricht On the shape of the 'petal' for the dissipation curve
23.04.2018 | Lobachevsky 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: BAM@Hannover Messe: innovative 3D printing method for space flight

At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.

Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...

Im Focus: Molecules Brilliantly Illuminated

Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.

Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Quantum Technology for Advanced Imaging – QUILT

24.04.2018 | Information Technology

AWI researchers measure a record concentration of microplastic in arctic sea ice

24.04.2018 | Earth Sciences

Complete skin regeneration system of fish unraveled

24.04.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>