Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Two photons strongly coupled by glass fiber

03.11.2014

At the Vienna University of Technology, 2 photons have been made to interact strongly using an ultra-thin glass fiber; This technique is an important new tool for quantum technology

Two photons in free space do not interact. Light waves can pass through each other without having any influence on each other at all. For many applications in quantum technology, however, interaction between photons is crucial.


The light in a glass fiber is coupled to a bottle resonator.

Credit: TU Wien


Light runs around a bottle-shaped glass fiber, about half as thick as a human hair.

Credit: TU Wien

It is an indispensable prerequisite for transmitting information through tap-proof quantum channels or for building optical logic gates. At the Vienna University of Technology (TU Wien), scientists have now succeeded in establishing a strong interaction between two single photons. This opens up completely new possibilities for quantum optics. The experimental results have now been published in the journal "Nature Photonics".

Interaction Usually Requires Bright Light

"In order to have light interact with light, people have been using so-called nonlinear media", says Professor Arno Rauschenbeutel (Institute for Atomic and Subatomic Physics, TU Wien). The light has an effect on the properties of these materials, and the material in turn influences the light, which leads to an indirect coupling between photons. This technique, however, can only be used at strong light intensities, when countless photons are involved.

At TU Wien, a system was built which creates a strong interaction between only two photons. This interaction is so strong that the phase of the photons is changed by 180 degrees. "It is like a pendulum, which should actually swing to the left, but due to coupling with a second pendulum, it swings to the right. There cannot be a more extreme change in the pendulum's oscillation", says Rauschenbeutel. "We achieve the strongest possible interaction with the smallest possible intensity of light."

A Photon in a Bottle

To make this possible, the photon has to be sent on an unlikely journey. An ultra-thin glass fibre is coupled to a tiny bottle-like light resonator so that light can partly enter the resonator, move in circles and return to the glass fibre. This detour through the resonator leads to the phase of the photon being inverted: a wave crest appears where a wave trough would have been expected.

When, however, a single rubidium atom is coupled to the resonator, the system is changed dramatically. Due to the presence of the atom, hardly any light enters the resonator anymore and the oscillation phase of the photon cannot be inverted.

Two Photons at Once

Things change when two photons arrive at the same time. "The atom is an absorber which can be saturated", says Arno Rauschenbeutel. "A photon is absorbed by the atom for a short while and then released into the resonator. During that time, it cannot absorb any other photons. If two photons arrive simultaneously, only one can be absorbed, while the other can still be phase shifted."

From a quantum mechanical point of view, there is no difference between the two photons. They can only be understood as a joint wave-like object, which is located in the resonator and in the glass fibre at the same time. The photons are indistinguishable. No one can tell which of them is being absorbed and which one has passed. When both hit the resonator at the same time, both of them together experience a phase shift by 180 degrees. Two interacting photons arriving simultaneously show a completely different behaviour than single photons.

The Building Blocks of Future Quantum Data-Highways?

"That way, a maximally entangled photon state can be created", says Arno Rauschenbeutel. "Such states are required in all fields of quantum optics – in quantum teleportation, or for light-transistors which could potentially be used for quantum computing."

A big advantage of the new system is that it is based on glass fibre technology, which is already being used for online communication anyway. Nano glass fibres and bottle-resonators are perfectly compatible with existing technologies. The targeted creation of a strong photon-photon-interaction is an important step towards a worldwide quantum information network for the tap-proof transmission of data.

Further information:

Prof. Arno Rauschenbeutel
Insitute for Atomic and Subatomic Physics
Vienna Center for Quantum Science and Technology
TU Wien
Stadionallee 2, 1020 Wien
T: +43-1-58801-141761
arno.rauschenbeutel@tuwien.ac.at

Dr. Jürgen Volz
Insitute for Atomic and Subatomic Physics
Vienna Center for Quantum Science and Technology
TU Wien
Stadionallee 2, 1020 Wien
T: +43-1-58801-141739
juergen.volz@tuwien.ac.at

Florian Aigner | EurekAlert!
Further information:
http://www.tuwien.ac.at/tu_vienna/

More articles from Physics and Astronomy:

nachricht The moon is front and center during a total solar eclipse
24.07.2017 | NASA/Goddard Space Flight Center

nachricht Superluminous supernova marks the death of a star at cosmic high noon
24.07.2017 | Royal Astronomical 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: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

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...

Im Focus: The proton precisely weighted

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...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

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....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

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,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

Ultrathin device harvests electricity from human motion

24.07.2017 | Power and Electrical Engineering

Scientists announce the quest for high-index materials

24.07.2017 | Materials Sciences

ADIR Project: Lasers Recover Valuable Materials

24.07.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>