  As a probe to explore the ability of invisibility cloaks to conceal objects
in the quantum mechanics domain, we study the spontaneous emission rate of an
excited two-level atom in the vicinity of an ideal invisibility cloaking. On
this base, first, a canonical quantization scheme is presented for the
electromagnetic field interacting with atomic systems in an anisotropic,
inhomogeneous and absorbing magnetodielectric medium which can suitably be used
for studying the influence of arbitrary invisibility cloak on the atomic
radiative properties. The time dependence of the atomic subsystem is obtained
in the Schrodinger picture. By introducing a modified set of the spherical wave
vector functions, the Green tensor of the system is calculated via the
continuous and discrete methods. In this formalism, the decay rate and as well
the emission pattern of the aforementioned atom are computed analytically for
both weak and strong coupling interaction, and then numerically calculations
are done to demonstrate the performances of cloaking in the quantum mechanics
domain. Special attention is paid to different possible orientations and
locations of atomic system near the spherical invisibility cloaking. Results in
the presence and the absence of the invisibility cloak are compared. We find
that the cloak works very well far from its resonance frequency to conceal a
macroscopic object, whereas at near the resonance frequency the object is more
visible than the situation that the object is not covered by the cloak.
