  We present a combined classical and quantum electrodynamics description of
the coupling between two circularly-polarized quantum emitters held above a
metal surface supporting surface plasmons. Depending on their position and
their natural frequency, the emitter-emitter interactions evolve from being
reciprocal to nonreciprocal, which makes the system a highly tunable platform
for chiral coupling at the nanoscale. By relaxing the stringent material and
geometrical constraints for chirality, we explore the interplay between
coherent and dissipative coupling mechanisms in the system. Thus, we reveal a
quasi-chiral regime in which its quantum optical properties are governed by its
subradiant state, giving rise to extremely sharp spectral features and strong
photon correlations.
