  Building large-scale superconducting quantum circuits will require
miniaturisation and integration of supporting devices including microwave
circulators, which are currently bulky, stand-alone components. Here we report
the realisation of a passive on-chip circulator which is made from a loop
consisting of three tunnel-coupled superconducting islands, with DC-only
control fields. We observe the effect of quasiparticle tunnelling, and we
dynamically classify the system into different quasiparticle sectors. When
tuned for circulation, the device exhibits strongly non-reciprocal 3-port
scattering, with average on-resonance insertion loss of 2 dB, isolation of 14
dB, power reflectance of -11 dB, and a bandwidth of 200 MHz.
