An open quantum system operated at the spectral singularities where
dimensionality reduces, known as exceptional points (EPs), demonstrates
distinguishing behavior from the Hermitian counterpart. Based on the recently
proposed microcavity with exceptional surface (ES), we report and explain the
peculiar quantum dynamics in atom-photon interaction associated with EPs:
cavity transparency, decoherence suppression beyond the limitation of
Jaynes-Cummings (JC) system, and the population trapping of lossy cavity. An
analytical description of the local density of states (LDOS) for ES microcavity
is derived from an equivalent cavity quantum electrodynamics (QED) model, which
goes beyond the single-excitation approximation and allows exploring the
quantum effects of EPs on multiphoton process by parametrizing the extended
cascaded quantum master equation. It reveals that a square Lorentzian term in
LDOS induced by second-order EPs interferes with the linear Lorentzian profile,
giving rise to cavity transparency for atom with special transition frequency
in the weak coupling regime. This additional contribution from EPs also breaks
the limit on dissipation rate of JC system bounded by bare components,
resulting in the decoherence suppression with anomalously small decay rate of
the Rabi oscillation and the long-time dynamics. Remarkably, we find that the
cavity population can be partially trapped at EPs, achieved by forming a bound
dressed state in the limiting case of vanishing atom decay. Our work unveils
the exotic phenomena unique to EPs in cavity QED systems, which opens the door
for controlling light-matter interaction at the quantum level through
non-Hermiticity, and holds great potential in building high-performance
quantum-optics devices.Comment: 11 pages, 6 figure