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.2013.377Further information:
Email: p.michler (at) ihfg.uni-stuttgart.de
Andrea Mayer-Grenu | idw
Astronomers discover dizzying spin of the Milky Way galaxy's 'halo'
26.07.2016 | NASA/Goddard Space Flight Center
Lonely Atoms, Happily Reunited
26.07.2016 | Technische Universität Wien
Transparent electronics devices are present in today’s thin film displays, solar cells, and touchscreens. The future will bring flexible versions of such devices. Their production requires printable materials that are transparent and remain highly conductive even when deformed. Researchers at INM – Leibniz Institute for New Materials have combined a new self-assembling nano ink with an imprint process to create flexible conductive grids with a resolution below one micrometer.
To print the grids, an ink of gold nanowires is applied to a substrate. A structured stamp is pressed on the substrate and forces the ink into a pattern. “The...
A new Fraunhofer MEVIS method conveys medical interrelationships quickly and intuitively with innovative visualization technology
On the monitor, a brain spins slowly and can be examined from every angle. Suddenly, some sections start glowing, first on the side and then the entire back of...
Researchers at the U.S. Department of Energy's (DOE) Ames Laboratory have discovered an unusual property of purple bronze that may point to new ways to achieve high temperature superconductivity.
While studying purple bronze, a molybdenum oxide, researchers discovered an unconventional charge density wave on its surface.
Munich Physicists have developed a novel electron microscope that can visualize electromagnetic fields oscillating at frequencies of billions of cycles per second.
Temporally varying electromagnetic fields are the driving force behind the whole of electronics. Their polarities can change at mind-bogglingly fast rates, and...
Breakup of continents with two speed: Continents initially stretch very slowly along the future splitting zone, but then move apart very quickly before the onset of rupture. The final speed can be up to 20 times faster than in the first, slow extension phase.phases
Present-day continents were shaped hundreds of millions of years ago as the supercontinent Pangaea broke apart. Derived from Pangaea’s main fragments Gondwana...
15.07.2016 | Event News
15.07.2016 | Event News
11.07.2016 | Event News
27.07.2016 | Earth Sciences
27.07.2016 | Materials Sciences
27.07.2016 | Earth Sciences