  We detail techniques to optimise high-level classical simulations of Shor's
quantum factoring algorithm. Chief among these is to examine the entangling
properties of the circuit and to effectively map it across the one-dimensional
structure of a matrix product state. Compared to previous approaches whose
space requirements depend on $r$, the solution to the underlying order-finding
problem of Shor's algorithm, our approach depends on its factors. We performed
a matrix product state simulation of a 60-qubit instance of Shor's algorithm
that would otherwise be infeasible to complete without an optimised
entanglement mapping.
