  In this Letter, we show that the fulfillment of uncertainty relations is a
sufficient criterion for a quantum-mechanically permissible state. We
specifically construct two pseudo-spin observables for an arbitrary
non-positive Hermitian matrix whose uncertainty relation is violated. This
method enables us to systematically derive separability conditions for all
negative partial-transpose states in experimentally accessible forms. In
particular, generalized entanglement criteria are derived from the
Schrodinger-Robertson inequalities for bipartite continuous-variable states.
