  Photonic bound states in the continuum (BICs) are special localized and
non-decaying states of a photonic system with a frequency embedded into the
spectrum of scattered states. The simplest photonic structure displaying a
single BIC is provided by two waveguides side-coupled to a common waveguide
lattice, where the BIC is protected by symmetry. Here we consider such a simple
photonic structure and show that, breaking mirror symmetry and allowing for
non-nearest neighbor couplings, a doublet of quasi-BIC states can be sustained,
enabling weakly-damped embedded Rabi oscillations of photons between the
waveguides.
