  We introduce a one-way, one-quantum cascade, whereby a single excitation
proceeds one-directionwise in a ladder of energy levels. This makes a variation
from more famous two-way cascades where the excitation can go up and down
following its excitation or relaxation in the ladder. We provide closed-form
solutions for two-photon correlation functions between any transitions in such
circular cascades. We discuss how the rich correlations that result from what
appears to be an extremely simple implementation, are essentially those which
have been entertained from complex architectures relying on
strongly-correlated, many-body physics or cavity QED effects.
