  We show that it is possible to uniquely reconstruct a generic many-body local
Hamiltonian from a single pair of initial and final states related by time
evolution with the Hamiltonian. We then propose a practical version of the
protocol involving multiple pairs of such initial/final states. Using the
eigenstate thermalization hypothesis, we provide bounds on the protocol's
performance and stability against errors from measurements and in the ansatz of
the Hamiltonian. The protocol is efficient (requiring experimental resources
scaling polynomially with system size in general and constant with system size
given translation symmetry) and thus enables analog and digital quantum
simulators to verify implementation of a putative Hamiltonian.
