  We consider Gaussian quantum circuits supplemented with non-Gaussian input
states and derive sufficient conditions for efficient classical strong
simulation of these circuits. In particular, we generalise the stellar
representation of continuous-variable quantum states to the multimode setting
and relate the stellar rank of the input non-Gaussian states, a recently
introduced measure of non-Gaussianity, to the cost of evaluating classically
the output probability densities of these circuits. Our results have
consequences for the strong simulability of a large class of near-term
continuous-variable quantum circuits.
