  The photon blockade (PB) effect in emitter-cavity systems depends on the
anharmonicity of the ladder of dressed energy eigenstates. The recent
developments in color center photonics are leading toward experimental
demonstrations of multi-emitter-cavity solid-state systems with an expanded set
of energy levels compared to the traditionally studied single-emitter systems.
We focus on the case of N = 2 nonidentical quasi-atoms strongly coupled to a
nanocavity in the bad cavity regime (with parameters within reach of the color
center systems), and discover three PB mechanisms: polaritonic, subradiant and
unconventional. The polaritonic PB, which is the conventional mechanism studied
in single-emitter-cavity systems, also occurs at the polariton frequencies in
multi-emitter systems. The subradiant PB is a new interference effect owing to
the inhomogeneous broadening of the emitters which results in a purer and a
more robust single photon emission than the polaritonic PB. The unconventional
PB in the modeled system corresponds to the suppression of the single- and
two-photon correlation statistics and the enhancement of the three-photon
correlation statistic. Using the effective Hamiltonian approach, we unravel the
origin and the time-domain evolution of these phenomena.
