  Characterization of qubit couplings in many-body quantum systems is essential
for benchmarking quantum computation and simulation. We propose a tomographic
measurement scheme to determine all the coupling terms in a general many-body
Hamiltonian with arbitrary long-range interactions, provided the energy density
of the Hamiltonian remains finite. Different from quantum process tomography,
our scheme is fully scalable with the number of qubits as the required rounds
of measurements increase only linearly with the number of coupling terms in the
Hamiltonian. The scheme makes use of synchronized dynamical decoupling pulses
to simplify the many-body dynamics so that the unknown parameters in the
Hamiltonian can be retrieved one by one. We simulate the performance of the
scheme under the influence of various pulse errors and show that it is robust
to typical noise and experimental imperfections.
