Fig. 2: Complete hierarchy for the marginal problem.
From: A complete hierarchy for the pure state marginal problem in quantum mechanics
In order to formulate the hierarchy for the marginal problem, one extends the two copies in Fig. 1 to an arbitrary number of copies N. If the marginal problem has a solution \(\left|\varphi \right\rangle\), then there are multi-party extensions ΦAB⋯Z in the symmetric subspace specified by \({V}_{{{\Sigma }}}={V}_{\sigma }^{\otimes n}\) for any number of copies, obeying some semidefinite constraints.
