  We investigate chiral emission and the single-photon scattering of spinning
cavities coupled to a meandering waveguide at multiple coupling points. It is
shown that nonreciprocal photon transmissions occur in the cavities-waveguide
system, which stems from interference effects among different coupling points,
and frequency shifts induced by the Sagnac effect. The nonlocal interference is
akin to the mechanism in giant atoms. In the single-cavity setup, by optimizing
the spinning velocity and number of coupling points, the chiral factor can
approach 1, and the chiral direction can be freely switched. Moreover,
destructive interference gives rise to the complete photon transmission in one
direction over the whole optical frequency band, with no analogy in other
quantum setups. In the multiple-cavity system, we also investigate the photon
transport properties. The results indicate a directional information flow
between different nodes. Our proposal provides a novel way to achieve quantum
nonreciprocal devices, which can be applied in large-scale quantum chiral
networks with optical waveguides.
