Elucidating Dicke superradiance by quantum uncertainty

Recently it was shown by Wolfe and Yelin E. Wolfe and S. F. Yelin, Phys. Rev. Lett. 112, 140402 (2014) that in the idealized Dicke model of superradiance there is no entanglement among any partitions of the system during the total evolution time of the system. This result immediately causes us to question if other measures from quantum information theory can explain the characteristic release of energy in a short time interval. In this work we identify the uncertainty of purely quantum origin as the property responsible for Dicke superradiance. The quantum uncertainty on the population of each emitter of the sample captured by the Wigner-Yanase skew information (WYSI) is proportional to the correlation radiation rate, which is the part of the total radiated power coming from dipole correlations and responsible for releasing in a short time a great intensity of radiation energy. We also show that the correlation measure called local quantum uncertainty, which is the minimization of the WYSI over all local observables, presents a double sudden change induced by the environment. The time window between these two sudden changes is used to define the interval in which symmetric global observables of the system behave classically for N, although the emitters remain strongly quantum correlated.