  For approximate inference in the generalized quadratic equations model, many
state-of-the-art algorithms lack any prior knowledge of the target signal
structure, exhibits slow convergence, and can not handle any analytic prior
knowledge of the target signal structure. So, this paper proposes a new
algorithm, Quadratic Message passing (QMP). QMP has a complexity as low as
$O(N^{3})$. The SE derived for QMP can capture precisely the per-iteration
behavior of the simulated algorithm. Simulation results confirm QMP outperforms
many state-of-the-art algorithms.
