Reviewed by Lexie CornerSep 3 2024
Under certain conditions, thousands of light particles can merge to form a "super photon," a phenomenon known as a Bose-Einstein condensate. Researchers at the University of Bonn have successfully manipulated the design of this condensate using "tiny nano molds." The findings are detailed in the journal Physical Review Letters.
By creating indents on the reflective surfaces - (shown on the left in an exaggerated form; the reflective surface is facing upwards), the researchers were able to imprint a structure onto the photon condensate (right). Image Credit: IAP/University of Bonn
This advancement enables researchers to arrange light into a simple lattice structure with four points of light in a square formation, potentially facilitating secure information exchange between multiple participants.
When multiple light particles are trapped in a confined space and cooled to extremely low temperatures, they lose their individual identities and behave as a single "super photon." This phenomenon, known as a Bose-Einstein condensate, typically appears as a hazy speck of light.
However, we have now managed to imprint a simple lattice structure on the condensate.
Andreas Redmann, Institute of Applied Physics, University of Bonn
To create super photons, the researchers at the Institute of Applied Physics (IAP) fill a small container with a dye solution, with the container's side walls reflecting light. When a laser excites the dye molecules, photons are produced, oscillating between the reflective surfaces.
Initially, these light particles are relatively warm, but as they repeatedly collide with the dye molecules, they cool down and eventually condense into a super photon.
Unevenness on the Reflective Surfaces Influences the Design of the Condensate
The reflective surfaces are normally perfectly smooth. We decided to deliberately add small indents to them, which, figuratively speaking, provide more space for the light to collect in them.
Andreas Redmann, Institute of Applied Physics, University of Bonn
This effectively imprints a structure onto the condensate, similar to pressing a mold with one closed side down into a sandbox: when it is lifted out, the imprint of the mold remains visible in the sand.
“In this way, we have managed to create four regions where the condensate prefers to stay,” said Redmann.
It is similar to dividing a bowl of water into four quadratic-shaped cups. But unlike water, the super photon would not always break up into four smaller pieces. It stays as a single condensate if the cups are spaced closely enough apart to allow light particles to go back and forth between them quantum mechanically.
This characteristic could be utilized to produce so-called quantum entanglement. If the light in one cup changes, the light in the other cups will be affected. To ensure that information exchanges between multiple participants are tap-proof, there must be a quantum physical correlation between the photons. Examples of such exchanges include talks and covert transactions.
By deliberately changing the form of the reflective surfaces, it is theoretically possible to create Bose-Einstein condensates that are split between 20, 30, or even more lattice sites. This would allow us to make the communication between lots of participants in a discussion tap-proof. Our study has shown for the first time how certain emission patterns can be deliberately created for use in a specific application. This makes the method extremely interesting for many different technological developments.
Andreas Redmann, Institute of Applied Physics, University of Bonn
The study was supported by the German Research Foundation (DFG), the European Union (ERC Starting Grant), and the German Aerospace Centre (DLR).
Journal Reference:
Redmann, A., et al. (2024) Bose-Einstein Condensation of Photons in a Four-Site Quantum Ring. Physical Review Letters. doi.org/10.1103/physrevlett.133.093602.