  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.

Quantum Physics