  We introduce an efficient method to reconstruct the Wigner function of
many-mode continuous variable systems. It is based on convex optimization with
semidefinite programs, and also includes a version of the maximum entropy
principle, in order to yield unbiased states. A key ingredient of the proposed
approach is the representation of the state in a truncated Fock basis. As a
bonus, the discrete finite representation allows to easily quantify the
entanglement.
