Suppose a have a circuit coded up in ProjectQ, suppose also it is that large to be hard enough to write it down as a unitary matrix by hands (e.g. order-finding, which is rather standard, but turns out to be very complex when you decompose the modular exponent into elementary 1- and 2-qubit gates, the typical Hilbert space size even for simple numbers would be $2^8-2^{10}$).
Can you propose or you maybe you already know an existing way how to obtain a unitary or even a product of unitaries that delivers the circuit results applied to initial state?
