  A geometry-based mechanism for inducing circulation of photons is illustrated
by a metastructure consisting of quantum dots arranged in a triangle coupled to
photonic structures. The coupling between the photons and the excitons in the
quantum dots leads to a photon blockade and limits the number of photons
participating in the transport. In the steady state described by the quantum
master equation of photons, the local photonic currents exhibit distinct
circulation patterns, which originate from the wave nature in a multi-path
geometry. The geometry-based mechanism does not require an artificial gauge
field from light-matter interactions. The phase diagrams showing where
different patterns of circulation can be found saturate as the number of
photons allowed on each site increases. By using the third-quantization
formalism, we show the circulation survives without any photon blockade in the
noninteracting case. Moreover, we demonstrate the decoupling of the direction
of the local current from the density difference and propose possible
applications of the local photonic transport.
