Nikolai Wyderka

The spectral variant of the quantum marginal problem asks: Given prescribed spectra for a set of quantum marginals, does there exist a compatible joint state? The main idea of this work is a symmetry-reduced semidefinite programming hierarchy for detecting incompatible spectra. The hierarchy is complete, in the sense that it detects every incompatible set of spectra. The refutations it provides are dimension-free, certifying incompatibility in all local dimensions. The hierarchy equally applies to the sums of Hermitian matrices problem, to optimize trace polynomials on the positive cone, to the compatibility of invariants, and to certify vanishing Kronecker coefficients.