Resonance Interaction Due to Quantum Coherence

Abstract

The interaction energy between two atoms is crucially dependent on the quantum state of the two‐atom system. In this paper, it is demonstrated that a steady resonance interaction energy between two atoms exists when the atoms are in a certain type of coherent superposition of single‐excitation states. The interaction is tree‐level classical in the sense of the Feynman diagrams. A quantity called quantum classicality is defined in the present paper, whose nonzero‐ness ensures the existence of this interaction. The dependence of the interatomic interaction on the quantum nature of the state of the two‐atom system may potentially be tested with Rydberg atoms.