Superradiance of non-interacting atoms

TL;DR

This paper investigates superradiance in non-interacting atoms, showing that quantum correlations generated by measurements can produce superradiant bursts even when atoms are widely separated, challenging traditional synchronization explanations.

Contribution

It demonstrates that superradiance can arise from measurement-induced quantum correlations in non-interacting atoms, extending understanding beyond the small sample limit.

Findings

Superradiant bursts occur in non-interacting atoms with large separations.

Quantum correlations from measurements can induce superradiance.

Superradiance is not solely due to atomic synchronization.

Abstract

Fully-excited two-level atoms separated by less than the transition wavelength cooperatively emit light in a short burst, a phenomenon called superradiance by R. Dicke in 1954. The burst is characterized by a maximum intensity scaling with the square of the number of atoms $N$ and a temporal width reduced by $N$ compared to the single atom spontaneous decay time. Both effects are usually attributed to a synchronization of the electric dipole moments of the atoms occurring during the process of light emission. Contrary to this explanation, it was recently shown by use of a quantum path description that the peak intensity results from the quantum correlations among the atoms when occupying symmetric Dicke states. Here we investigate from this perspective the temporal evolution of the ensemble, starting in the small sample limit, i.e., when the atoms have mutual separations much smaller than the transition wavelength $\lambda$ and pass down the ladder of symmetric Dicke states. In addition, we explore the temporal evolution for the case of non-interacting atoms with mutual separations much larger than $\lambda$. We show that in this case a similar superradiant burst of the emitted radiation is observed if the quantum correlations of the atoms are generated by conditional photon measurements retaining the atomic ensemble within or close to the symmetric subspace.