Super Photons Unveiled: Sculpting Light Into Unbreakable Communication Networks

By University of Bonn October 1, 2024

Collected at: https://scitechdaily.com/super-photons-unveiled-sculpting-light-into-unbreakable-communication-networks/

Physicists at the University of Bonn have developed a method to manipulate Bose-Einstein condensates of light by structuring the reflective surfaces of their container, resulting in super photons that can maintain a unified state across multiple quantum spaces.

This breakthrough offers new potential for creating secure quantum communications by leveraging the quantum entanglement properties of light, paving the way for tap-proof discussions and transactions across multiple parties.

Bose-Einstein Condensate of Light

When numerous light particles are cooled to a very low temperature and simultaneously confined in a compact space, they suddenly become indistinguishable from one another and behave like a single super photon. Physicists call this a Bose-Einstein condensate and it normally resembles a blurry speck of light. “However, we have now managed to imprint a simple lattice structure on the condensate,” says Andreas Redmann from the Institute of Applied Physics (IAP) at the University of Bonn.

The researchers at the IAP create super photons by filling a tiny container with a dye solution. The side walls of the container are reflective. If the dye molecules are excited with a laser, they produce photons that bounce back and forth between the reflective surfaces. These light particles start off relatively warm. However, they repeatedly collide with the dye molecules as they move between the reflective surfaces and cool down until they finally condense to form a super photon.

Structural Influence of Reflective Surfaces

“The reflective surfaces are normally perfectly smooth,” explains Redmann. “We decided to deliberately add small indents to them, which figuratively speaking provide more space for the light to collect in them.” This effectively imprints a structure onto the condensate – almost like when you press a mold with one closed side downwards into a sandbox: If you lift it up again, you can still see the imprint of the mold in the sand.

“In this way, we have managed to create four regions where the condensate prefers to stay,” says Redmann. It is as if you were to divide a bowl of water between four cups arranged in quadratic form. In contrast to water, however, the super photon will not necessarily split into four smaller portions. If the cups are positioned closely enough together so that the light particles can pass quantum mechanically back and forth between them, it remains as one single condensate.

Potential for Quantum Communication

This property could be used, for example, to create so-called quantum entanglement. If the light in one cup changes its state, it will also impact the light in the other cups. This quantum physical correlation between the photons is a basic requirement for making the exchange of information – such as discussions or secret transactions – between several participants tap-proof.

“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,” explains Redmann. “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.”

Reference: “Bose-Einstein Condensation of Photons in a Four-Site Quantum Ring” by Andreas Redmann, Christian Kurtscheid, Niels Wolf, Frank Vewinger, Julian Schmitt and Martin Weitz, 30 August 2024, Physical Review Letters.
DOI: 10.1103/PhysRevLett.133.093602

The project was funded by the German Research Foundation (DFG), the European Union (ERC Starting Grant) and the German Aerospace Centre (DLR).