ec 2 00 3 Structure of sufficient quantum coarse - grainings 1


Let H and K be finite dimensional Hilbert spaces, T : B(H) → B(K) be a coarse-graining and D1, D2 be density matrices onH. In this paper the consequences of the existence of a coarse-graining β : B(K) → B(H) satisfying βT (Ds) = Ds are given. (This means that T is sufficient for D1 and D2.) It is shown that Ds = ∑r p=1 λs(p)S H s (p)R (p) (s = 1, 2) should… (More)