  Nonhermitian systems provide new avenues to create topological defect states.
An unresolved general question is how much the formation of these states
depends on asymmetric backscattering, be it nonreciprocal as in the
nonhermitian skin effect or reciprocal as encountered between the internal
states of asymmetric microresonators. Here, we demonstrate in a concrete,
practically accessible setting of a lossy coupled-resonator optical waveguide
that nonhermitian defect states can exist in open optical systems due to
lifetime differences, without the need for asymmetric backscattering within or
between the individual resonators. We apply our findings to a finite system of
coupled circular resonators perturbed by nanoparticles, following the concept
of creating an interface by inverting the position of the nanoparticles in half
of the chain. We compare a coupled-mode tight-binding approximation to
full-wave numerical simulations, showing that spectrally isolated defect states
can indeed be implemented in this simple nonhermitian photonic device.
