Realization of superabsorption by time reversal of superradiance

Abstract

Emission and absorption of light lie at the heart of light-matter interaction(1). Although emission and absorption rates are regarded as intrinsic properties of atoms and molecules, various ways to modify these rates have been sought in applications such as quantum information processing(2), metrology(3) and light-energy harvesting(4). One promising approach is to utilize collective behaviour of emitters in the same way as in superradiances. Although superradiance has been observed in diverse systems(3,6-10), its conceptual counterpart in absorption has never been realized(11) until now. Here we demonstrate enhanced cooperative absorption-superabsorption-by implementing a time-reversal process of superradiance. The observed superabsorption rate is much higher than that of ordinary absorption, with the number of absorbed photons scaling with the square of the number of atoms, exhibiting the cooperative nature of superabsorption. The present superabsorption-which performs beyond the limitations of conventional absorption-can facilitate weak-signal sensing(1), light-energy harvesting(11) and light-matter quantum interfaces(2).