Separable States Violate the Complementary-Quantum Correlation Conjecture

Correlations measured in complementary local bases provide an experimentally accessible probe of the total correlations in a bipartite quantum state. The complementary-quantum correlation conjecture asserts that the sum of two such classical mutual informations never exceeds the premeasurement quantum mutual information. We disprove this conjecture in every local dimension $d\geq3$ with an explicit rank-two separable state. One of the two complementary measurements recovers the complete one-bit branch label, while the other retains additional classical correlation. For qutrits the excess is exactly $\frac13\log_2(3456/3125)=0.0484156759\ldots$ bits. Continuity yields full-rank separable violations. The effect therefore requires neither entanglement nor quantum discord; it arises from two complementary readouts of the same classical latent variable.

Source: arXiv:2608.03828v1 - http://arxiv.org/abs/2608.03828v1 PDF: https://arxiv.org/pdf/2608.03828v1 Original Link: http://arxiv.org/abs/2608.03828v1