Room-temperature single-photon turnstile
Secure data communication, quantum computation, and sensing devices benefit from light sources, which emit only one photon at a time. These light sources operate in a mode that is similar to a turnstile, allowing only one person to pass through at a time.
Such so-called single photon sources exist already, but with the technical drawback that they only work at ultracold temperatures close to absolute zero. Scientists of the center for Integrated Quantum Science and Technology (IQST) at the University of Stuttgart have now developed a microscopic platform, which could allow for such a turnstile operation, even at room temperature.
They use atom-filled hollow-core optical fibres. Their results were presented in Nature Communications on June 19th 2014.
It is unimaginable to live without the benefits of light in our modern world. We take advantage of light to transmit information around the world through optical fibres, to read out BlueRay discs, and to perform surgeries. That light can be used for many diverse applications lies in its versatile nature. Different light sources produce different types of light.
The subtle differences between light sources, relies on how the light particles, so called photons, leave the light source. Ordinary light bulbs produce quite irregular light. Here, the photons tend to bunch and to exit in groups. Laser light is more regular, but still groups of photons can appear. For some novel technologies researchers ask for even more regular light.
The photons shall leave the light source one by one, like behind a turnstile. Only with these well-separated photons can one fully exploit the quantum mechanical properties of single photons, e.g. for secure data communication. Such sources do exist already, but they can only be operated at extremely low temperatures with lab-filling setups, that are not compatible with real life technologies.
Researchers from IQST at the University of Stuttgart and the Max Planck Institute for the Science of Llght in Erlangen have now made an important step towards a photon-turnstile that can operate at room temperature.
Robert Löw and his team want to exploit an already known scheme to realize their room-temperature photon turnstile. Scientists working with Sebastian Hofferberth, a researcher also from the University of Stuttgart, have done the following experiment: An ultracold gas of atoms is irradiated with ordinary laser light at a specific wavelength and is absorbed by the gas.
A second laser beam, set to a different wavelength, is then turned on and sent through the gas, making the gas transparent for the first laser beam. The crucial step to create single photons is to excite the atoms in the gas to very high energy levels. These so-called Rydberg atoms are typically 1000’s of times larger than ordinary atoms and are very sensitive. Due to their sensitivity they strongly influence each other, which reduces the transparency effect caused by the second laser beam. More precisely, quantum mechanics takes care that only one photon per time can pass.
This is the starting point for the experiments with hollow core photonic crystal fibres, which are now filled with a room-temperature atomic gas. The laser light is collimated inside the fibre providing the necessary high-intensity light for the optical non-linear response over longer distances than would be possible in free space. Therefore many more Rybergs atoms can be created along the length of the fibre.
The scientists are convinced that the usage of the fibre will make the observation of the turnstile-effect possible even at room temperatures. The problem is the high velocity of the atoms whizzing back and forth in the fibre and eventually colliding with the fibre walls, which ruins the turnstile effect. The hope is that the many more Rydberg atoms in the fibre could compensate for this short lifetime and still sort the photons as desired.
One major concern towards this goal has now been ruled out by the Stuttgart team: The core of the fibre with 19 microns diameter is only marginally larger than the Rydberg atoms and is very likely to perturb the Rydberg atoms and by this the turnstile-effect. The question has been if caged Rydberg atoms behave differently than free range Rydberg atoms and the answer is no. The Rydbergs atoms do not feel the wall until they crash into them. Collisions happen very often, but the time in between wall collisions should be sufficient to realize a photon turnstile.
*Originalpublikation: G. Epple, K. S. Kleinbach, T. G. Euser, N. Y. Joly, T. Pfau, P. St.J. Russell, R. Löw: "Rydberg atoms in hollow-core photonic crystal fibres", Nature Communications 5 4132 (2014)
Weitere Informationen: Robert Löw, Universität Stuttgart, 5. Physikalisches Institut,
Tel. +49 711 685 64954, E-Mail: email@example.com
Andrea Mayer-Grenu | idw - Informationsdienst Wissenschaft
Pulses of electrons manipulate nanomagnets and store information
21.07.2017 | American Institute of Physics
Vortex photons from electrons in circular motion
21.07.2017 | National Institutes of Natural Sciences
Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.
For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...
What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.
To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...
The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....
A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...
Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision
Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...
21.07.2017 | Event News
19.07.2017 | Event News
12.07.2017 | Event News
21.07.2017 | Earth Sciences
21.07.2017 | Power and Electrical Engineering
21.07.2017 | Physics and Astronomy