Exotic quantum states made from light

August 14, 2017, University of Bonn
The artist's rendering shows how potential wells are created for the light in the microresonator through heating with an external laser beam (green). Credit: David Dung, Universität Bonn

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are sufficiently concentrated and cooled. The individual particles merge with each other, making them indistinguishable. Researchers call this a photonic Bose-Einstein condensate. It has long been known that normal atoms form such condensates. Prof. Martin Weitz from the Institute of Applied Physics at the University of Bonn attracted attention among experts in 2010 when he produced a Bose-Einstein condensate from photons for the first time.

In his latest study, Prof. Weitz' team experimented with this kind of super-photon. In the experimental setup, a laser beam was rapidly bounced back and forth between two mirrors. In between was a pigment that cooled the laser to such an extent that a super-photon was created from the individual light portions. "The special thing is that we have built a kind of optical well in various forms, into which the Bose-Einstein condensate was able to flow," reports Weitz.

A polymer varies the light path

The team of researchers used a trick here: It mixed a into the pigment between the mirrors, which changed its refractive index depending on the temperature. The route between the mirrors for the light thus changed so that longer light wavelengths passed between the mirrors when heated. The extent of the light path between the mirrors could be varied, in that the polymer could be warmed via a very thin heating layer.

"With the help of various temperature patterns, we were able to create different optical dents," explains Weitz. The geometry of the mirror only appeared to warp, while the of the polymer changed at certain points - however, this had the same effect as a hollow shape. Part of the super-photon flowed into this apparent well. In this way, the researchers were able to use their apparatus to create different, very low-loss patterns that captured the photonic Bose-Einstein condensate.

Precursor of quantum circuits

The team of researchers investigated in detail the formation of two neighboring wells, controlled via the temperature pattern of the polymer. When the light in both optical hollows remained at a similar energy level, the super-photon flowed from one well into the neighboring one. "This was a precursor of optical quantum circuits," highlighted the physicist at the University of Bonn. "Perhaps even complex arrangements, for which quantum entanglement occurs in interaction with a possible photon interaction in suitable materials, can be produced with this experimental setup."

This would, in turn, be the prerequisite for a new technique for quantum communication and computers. "But that's still a long way off," says Weitz. The findings by the research team could also conceivably be used to further develop lasers - for instance for highly precise welding work.

Explore further: Measuring the heat capacity of condensed light

More information: Variable Potentials for Thermalized Light and Coupled Condensates, Nature Photonics (2017). DOI: 10.1038/nphoton.2017.139

Related Stories

Measuring the heat capacity of condensed light

April 19, 2016

Liquid water is a very good heat storage medium – anyone with a Thermos bottle knows that. However, as soon as water boils or freezes, its storage capacity drops precipitously. Physicists at the University of Bonn have ...

German physicists create a 'super-photon'

November 24, 2010

Physicists from the University of Bonn have developed a completely new source of light, a so-called Bose-Einstein condensate consisting of photons. Until recently, expert had thought this impossible. This method may potentially ...

Researchers obtain supersolidity state experimentally

March 2, 2017

When matter is cooled to near absolute zero, intriguing phenomena emerge. These include supersolidity, where crystalline structure and frictionless flow occur together. ETH researchers have succeeded in realising this strange ...

A stream of superfluid light

June 5, 2017

Scientists have known for centuries that light is composed of waves. The fact that light can also behave as a liquid, rippling and spiraling around obstacles like the current of a river, is a much more recent finding that ...

Recommended for you

Information engine operates with nearly perfect efficiency

January 19, 2018

Physicists have experimentally demonstrated an information engine—a device that converts information into work—with an efficiency that exceeds the conventional second law of thermodynamics. Instead, the engine's efficiency ...

Artificial agent designs quantum experiments

January 19, 2018

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered ...

3 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

zave
Aug 15, 2017
This comment has been removed by a moderator.
Whydening Gyre
not rated yet Aug 15, 2017
Electrons are always exactly the same charge. Make it "bigger" and it is no longer an electron.
Dingbone
Aug 15, 2017
This comment has been removed by a moderator.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.