Decay of Atomic States

Qian Bin, Xin‐You Lü

We investigate theoretically the collective radiance characteristics of an atomic ensemble with the simultaneous decay of two atoms. We show that the two-atom decay can significantly suppress the steady-state collective radiance of the atoms, expanding the region of subradiance. In the steady-state subradiance regime, the system is in an entangled state, and the mean populations of the system in the excited state and ground state of the atoms are almost equal. The processes of the two-atom decay can be demonstrated by the population distribution of the system state on the Dicke ladder. Moreover, we show the correlation property of the emitted light from the atomic ensemble, where the correlation function is rewritten in the presence of the two-atom decay. We find that the emitted photons of steady state only show bunching in the case of two-atom decay. This work broadens the realm of collective radiance, with potential applications for quantum information processing.

Thad Gilbert Walker

Mihailović, M. V.

Martin Hebenstreit, Barbara Kraus, Laurin Ostermann +1 more

Spontaneous emission of atoms in free space is modified by the presence of other atoms in close vicinity inducing collective super- and subradiance. For two nearby atoms with a single decay channel the entangled antisymmetric superposition state of the two single excited states will not decay spontaneously. No such excited two-atom dark state exists, if the excited state has two independent optical decay channels of different frequencies or polarizations. However, we show that for an excited atomic state with N-1 independent spontaneous decay channels one can find a highly entangled N-particle dark state, which completely decouples from the vacuum radiation field. It does not decay spontaneously, nor will it absorb resonant laser light. Mathematically, we see that this state is the only such state orthogonal to the subspace spanned by the atomic ground states. Moreover, by means of generic numerical examples we demonstrate that the subradiant behavior largely survives at finite atomic distances including dipole-dipole interactions.

Shi-Yao Zhu, L. Z. Wang, H. Fearn

The decay of the active atoms in micromasers is theoretically analyzed. The equations of motion for the diagonal elements of the micromaser field, which include an atomic-decay effect, have been obtained. The relation between the photon statistics and the micromaser field on the atomic decay has been studied. The effect of atomic-decay rates and average photon numbers, photon-number variances, and the photon-number distribution has been discussed. It has been shown that generation of approximate trapping states or number states requires very small atomic-decay rates and very large field-atom coupling constants.