ИСТИНА

The concept of Rydberg blockade is widely used now in various branches of physics, such as dynamics of ultracold gases, quantum optics, quantum information, etc. However, all previous studies considered the blockade of only the excitation with the same value of the principal quantum number n as in the original Rydberg atom. In such a case, the blocked zone represents just a solid ball around the already excited atom. The aim of our work was to take into account the excitation to the states with neighboring values of the principal quantum number (e.g., n-1 or n+1). As a result, we have found that the blocked zone possesses a much more complex structure. Namely, it is composed of a number of co-centric shells; so that the Rydberg excitation becomes unblocked again in a certain range of sufficiently small distances from the central atom [Yu.V. Dumin. J. Phys. B, v.47, p.175502 (2014)]. One important consequence of this effect is that it should reduce the total efficiency of the Rydberg blockade (which is of vital importance, e.g., for the quantum processing protocols). Yet another consequence of the fine structure is that it can facilitate formation of the Rydberg molecules and crystals, whose emergence would otherwise be precluded by the complete blockade.