A unique experiment has been conducted in Germany, which showed, how two atoms are bound with each other through one electron, becoming a molecule-“butterfly”. Scientists claim that this is one more step to the creation of quantum computers and molecular machines.

Molecules-“butterflies”, or Rydberg molecules, are composed of 2 atoms, a usual one and a Rydberg one: one of the electrons of its outer shell is in    highly excited state. People learnt to bind them several years ago, but they have not been studied properly because of instability.

Scientists of Kaiserslautern University of Technology under the supervision of Prof. Herwig Ott have held an experiment with the support of researchers from Purdue University (the USA). Rubidium was dispersed in a vacuum camera and frozen to 100 nK. Clouds from rubidium atoms acquired exotic aggregate state, Bose-Einstein condensate. It is easy to manipulate atoms’ properties in this state. Rydberg molecule was created with the help of a laser pulse, scientists attacked it with laser beams and saw for the first time, how atom electrons evolve around nuclei by orbits, reminding of butterfly wings by their form. Researchers also measured power, with which Rydberg atoms connect to each other through an electron.

Molecules-“butterflies” have many unusual properties. For example, they have dipole moments (there are zones with partially positive and negative charges) despite having 2 same atoms. This makes it easy to move it in weak electric fields. The results of the experience of German scientists can accelerate the development of quantum computers and molecular machines, devices, that can manipulate single atoms and molecules. Rydberg atoms have been long considered by physicists as a basis for qubits, elementary cells for storing data in computers. However, scientists have until recently experienced difficulties when trying to manipulate the Rydberg atoms. Using molecules-"butterflies" will help solve this problem.

The correspondent of the newspaper "Rosatom Country " asked Professor of Physics and Astronomy at the University of Purdue Chris Green, who stood at the origins of the theory of Rydberg molecules, a few questions.

- How long have you been preparing to catch molecule-"butterfly"?

- The existence of such molecules was predicted in 2002. Journal of Physics published two articles about it with a small interval. One was published by a group of scientists, immigrants from the USSR, who worked in the United States: Ilya Fabrikant, Gennady Chibisov, and Amiran Huskivadze. The second was written by me in collaboration with Edward Hamilton and Hossein Sadeghpour. After that there were several theoretical predictions. And then, finally, an experience that helped to explore "butterfly" in all the quantum mechanical details. I worked on the theoretical side of the opening.

- What does this discovery mean for science?

- This is a confirmation of ideas about molecules-"butterflies". The experiment helped to learn a lot about quantum-mechanical behavior of these intriguing molecules, which is difficult to understand, using modern standard quantum-chemical methods and computer programs. We opened the way for the creation of unusual molecules, that can be manipulated, using a strong interaction with the weak fields.

- What are you and your colleagues are doing in this area now?

- We continue to explore this phenomenon. It is necessary to confirm our results in many other independent experiments.

An employee of MEPhI department №70, Head of the RAS Laboratory for High Energy Densities Boris Zelener commented on this discovery, speaking about its significance and talked about similar studies in Russia.

- In Russia, interaction of Rydberg atoms has been studied by our Institute and the Institute of Semiconductor Physics in Novosibirsk. We are studying the interaction of Rydberg atoms, obtained by means of a magnetic-optical trap and the resonant two-photon excitation in the lithium-7 atoms at the temperature of 10-4 to 10-3 K.

The opening of our Western colleagues is a beautiful confirmation of the existence of such molecules and clusters of highly excited atoms, as well as three-dimensional similar to grids in solids, but with a much larger grid constant - of the order of a micron. Knowledge of the self-assembled structures of Rydberg atoms will create not only quantum computers, but metamaterials, and an opportunity to manipulate the atoms of antimatter.