Ultra-strong coupling between photons and atoms

TMO University researchers in Russia have demonstrated that individual atoms can be transformed into polaritons. In this new state of matter, photons and atoms form ultra-strong coupling for the first time. The results of this research can be used to control the properties of light and matter and to create quantum memory.

Materials’ properties can be changed chemically, by mixing them with other substances, or physically, as when metals enter superconductive states during rapid cooling. ITMO University physicists have performed similar transformations in a relatively new way—by using light and subjecting matter to high-intensity light beams or creating conditions for ultra-strong coupling between atoms and photons, which results in new particles known as polaritons.

The most commonly employed way to provide conditions for ultra-strong coupling is by using optical resonators. These resonators let the light in but don’t let the photons out easily. They are repeatedly reflected from the inner walls of the resonator, constantly interacting with the atoms inside. Thus, after being bombarded with photons, atoms form ultra-strong bonds with them, which facilitates the creation of quasiparticles.

The team have, first of all, found a way to provide stronger communication between light and matter, and second, to subject a whole array of atoms to light. For instance, they demonstrated that using a optical fiber waveguide instead of a resonator is a more promising method of changing states of matter.

The ultra-strong coupling state demonstrated by ITMO physicists partially solves the problem of quantum memory: its instability. (Phys.org)

The paper has been published in Physical Review Letters.

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