Researchers from the Technical University of Vienna (Austria) have made a theoretical breakthrough in the field of quantum communication. They have demonstrated that by using a special lens, it is possible to achieve the transfer of a single photon from one atom to another with high accuracy. This process is likened to a game of ping-pong, where atoms “throw” a photon to each other.
Professor Stefan Rotter from the Institute of Theoretical Physics at the University of Vienna explains that under normal conditions, when an atom emits a photon in free space, its direction is arbitrary, making it highly unlikely for another atom to intercept it. However, when the experiment is conducted in a closed environment, the dynamics change. This can be compared to the acoustic phenomenon of the “whispering gallery” where sound waves are reflected off the walls of an elliptical room, converging at a focus point, allowing people to hear each other at a significant distance.
Building upon the concept of Maxwell’s fishing lens, the research team has developed a method to direct photons from one atom to another. The lens, which has a variable refractive index, bends the light rays, ensuring they reach the target atom. First author Oliver Dikmann highlights the method’s efficiency compared to a simple elliptical environment, noting its enhanced performance and reduced sensitivity to atoms being perfectly aligned.
Professor Rotter adds that the light field within the lens comprises multiple oscillatory modes, similar to the sounds produced by a musical instrument. The researchers have demonstrated that by fine-tuning the connection between the atom and these fluctuations, the transmission of the photon from one atom to another can be nearly guaranteed, a stark contrast to the conditions encountered in free space.
After being absorbed, the photon leaves the atom in an excited state and is subsequently emitted again after a short time. This marks the start of a new cycle, where the roles of the atoms interchange, and the photon returns to its original atom.
While the effect has thus far only been demonstrated theoretically, practical experiments are feasible with modern technologies. Professor Rotter suggests that the effectiveness of the process could be further enhanced by employing not just two atoms, but two groups of atoms. This concept offers a promising starting point for the study of light-matter interactions at the quantum level.
The research findings have been published in the prestigious journal Physical Review Letters.