the intriguing particles that emerge when two photons couple

Scientists at the University of Bath in the UK have found a way to bind two photons of different colors together, paving the way for significant advances in quantum electrodynamics – the field of science that describes how light and matter interact . Over time, the team’s findings are likely to influence the development of optical and quantum communications, as well as accurate measurements of frequency, time, and distances.

Apple and wave: both have a mass

An apple that falls from a tree has speed and mass that give it momentum together. ‘Apple energy’ obtained by movement depends on the momentum and mass of the fruit.

Most people find the concept of momentum and energy (and therefore mass) easy to grasp when paired with solid objects. But the idea that non-material objects, such as light waves (everything from sunlight to laser radiation), also have a mass, is surprising to many. Among physicists, however, this is a known fact. This apparently paradoxical idea that waves have a mass indicates the place where quantum physics and the physical world meet.

The wave particle duality, proposed by the French physicist Louis de Broglie in 1924, is a powerful concept that describes how each particle or quantum entity can be described as a particle or a wave. Many so-called brush particles have been discovered that connect two different types of matter particles or light waves bound to a particle of material. A list of exotic brush particles contains phonons, plasmons, magnons and polaritons.

The team of physicists at Bath now have a way of creating brush particles that bind two different colored particles together. They call these formations photon-photon polaritons.

Photon-Photon Polaritons Detection

The opportunity to discover and manipulate photon photons is possible thanks to the relatively new development of high-quality microresonators. For light, microresonators serve as miniature racetracks, with photons zipping around the internal structure in the loops. The signature that leaves photon-photons in the light of the microresonator can be linked to the Autler-Townes effect, a peculiar phenomenon in quantum theory that describes strong photon-atom interactions. To achieve this effect in microresonators, a laser is set at the specific resonance frequency where a photon is expected to be absorbed, but no resonance absorption takes place. Instead, the photon-photon interaction forms two new resonant frequencies away from the old one.

An important feature that emerged from the Bath research is that the microresonator provided a whole series of split resonances, where each photon-photon pair displays its own momentum and energy, enabling the researchers to apply particle concept and calculate mass. According to the researchers’ predictions, photon photons are more than 1000 times lighter than electrons.

Professor Dmitry Skryabin, the physicist who led the research, said: “We now have a situation where microresonators – which are objects on a millimeter scale – act like giant atoms. The concept of artificial atoms is rapidly gaining ground in quantum space. electrodynamics of microwaves in superconducting circuits, while here we look at the similar opportunity in the optical range of frequencies.

“The small mass of photon-photons can lead to further development of very important analogies between light and liquids, where other families of brush particles are already in use.”

Ph.D. student Vlad Pankratov, who took part in the project, said: “After a year of models and data collection, it is incredibly exciting for us. The potential applications of our results are in the terabit and quantum optical communication schemes , and in the area of ​​precision measurements. “

The paper “Photon-photon polaritons in χ (2) microresonators” is published in Physical review research.