Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Always nicely in pairs and indistinguishable: Photons at the push of a button

20.02.2014
Encryption technologies with the help of quanta (quantum cryptography) or optical quantum computing require special light conditions, so-called indistinguishable and interlocked photon pairs, in well-defined temporal pulses.

Existing procedures to generate these, however, lead to results occurring more by chance in view of the number of photon pairs in one pulse. The consequences are errors in the quantum algorithms that greatly restrict their usefulness for deterministic quantum technologies that depend on the predictive accuracy.


Optical stimulation of a semi-conductor quantum point with a short laser pulse (green), that emits single interlocked quantum pairs (red resp. blue). Image: University of Stuttgart

In an experiment based on a semi-conductor quantum point, physicists from the University of Stuttgart have now shown how it is possible to generate single indistinguishable photon pairs based on parametric down conversion at the push of a button, so to speak. The work was published in the renowned specialist journal Nature Photonics*.

Semi-conductor quantum points are ideally suited to generate interlocked photon pairs due to their properties. In this way the quantum point can be stimulated through a short optical or electrical pulse, and subsequently a so-called photon pair based on parametric down conversion can be released if the conditions are suitable and be used for applications.

In the case of such photon pairs, the polarisation of each single photon is initially completely undefined. Only the targeted measurement on one of the two photons also enables a direct statement on the polarisation of the second photon, but this occurs immediately. In so doing it is irrelevant to what extent the single photons are separated from each other spatially. This property is exploited in a targeted way in the quantum technologies, for example for bug-proof communication.

In work up to now to generate interlocked photon pairs, the quantum points were optically stimulated electrically or in a non-resonant way. This method of stimulating, however, entails some disadvantages. In this respect, exactly two electron pair of holes are not stimulated for each stimulation pulse and subsequently two photons (an interlocked photon pair) emitted. It is rather the case that only one single proton or more than two photons are released. The fact that these stimulation conditions also generate many charge carriers in the environment of the quantum point is even more problematic. The interaction between these charge carriers and the charge carriers in the quantum point leads to so-called decoherence processes, that ultimately limit the indistinguishability of the photons.

Physicists at the Institute of Semiconductor Optics and Functional Interfaces under the management of Prof. Dr. Peter Michler have now succeeded of stimulating the quantum point with exactly two electron pair of holes with a so-called resonant two-photon stimulation process. Consequently, only one interlocked photon pair is emitted through this. Moreover, it was able to be shown that the photons generated in this resonant way are undistinguishable to a great extent, making them well suited for the aforementioned applications.

The more exact photon pair generation rate of 86 percent achieved in this way was able to be determined in cooperation with the theoretic physicist Dr. Martin Glässl from the University of Bayreuth. This joint work is now the starting point for a range of further experiments in which the photon source is to be used for experiments on the quantum teleportation of photons, for example.

* Original publication: M. Müller, S. Bounouar, K. D. Jöns, M. Glässl, and P. Michler, Nature Photonics, DOI 10.1038/nphoton.2013.377

Further information:
Prof. Dr. Peter Michler, Institute of Semi Semiconductor Optics and Functional Interfaces, Tel. 0711/685-64660,

Email: p.michler (at) ihfg.uni-stuttgart.de

Andrea Mayer-Grenu | idw
Further information:
http://www.ihfg.uni-stuttgart.de

More articles from Physics and Astronomy:

nachricht U of T astrophysicists offer proof that famous image shows forming planets
06.05.2015 | University of Toronto

nachricht The random raman laser: A new light source for the microcosmos
05.05.2015 | The Optical Society

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: Spray drying the precision particle under the virtual magnifying glass

Spray drying is a common manufacturing process, used in the production of ceramic granulate for technical components or dental prostheses as well as dissolvable medicinal substances, food additives and in the processing of milk into powder. Using computer simulation methodology developed by scientists at the Fraunhofer Institute for Mechanics of Materials IWM, a more comprehensible understanding can now be gained of the behavior of particles in solvent during the spray drying process. This allows powder and granulate manufacturers to specifically adjust the properties of their products while reducing waste.

Previously, it was unusual for granule and powder producers to use granulation simulations to improve their products. For new product development or process...

Im Focus: The random raman laser: A new light source for the microcosmos

Texas A&M University researchers demonstrate how a narrow-band strobe light source for speckle-free imaging has the potential to reveal microscopic forms of life

In modern microscope imaging techniques, lasers are used as light sources because they can deliver fast pulsed and extremely high-intensity radiation to a...

Im Focus: Pulsar with widest orbit ever detected

Discovered by high school research team

A team of highly determined high school students discovered a never-before-seen pulsar by painstakingly analyzing data from the National Science Foundation's...

Im Focus: Erosion, landslides and monsoon across the Himalaya

Scientists from Nepal, Switzerland and Germany was now able to show how erosion processes caused by the monsoon are mirrored in the sediment load of a river crossing the Himalaya.

In these days, it was again tragically demonstrated that the Himalayas are one of the most active geodynamic regions of the world. Landslides belong to the...

Im Focus: Through the galaxy by taxi - The Dream Chaser Space Utility Vehicle

A world-class prime systems integrator and electronic systems provider known for its rapid, innovative, and agile technology solutions, Sierra Nevada Corporation (SNC) is currently developing a new space transportation system called the Dream Chaser.

The ultimate aim is to construct a multi-mission-capable space utility vehicle, while accelerating the overall development process for this critical capability...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Green Summit 2015: the summit of the essential

05.05.2015 | Event News

HHL Energy Conference on May 11/12, 2015: Students Discuss about Decentralized Energy

23.04.2015 | Event News

“Developing our cities, preserving our planet”: Nobel Laureates gather for the first time in Asia

23.04.2015 | Event News

 
Latest News

Expedition Genomics Lab: the mobile revolution in genetic analysis

06.05.2015 | Life Sciences

How noise changes the way the brain gets information

06.05.2015 | Life Sciences

A model approach for sustainable phosphorus recovery from wastewater

06.05.2015 | Ecology, The Environment and Conservation

VideoLinks
B2B-VideoLinks
More VideoLinks >>>