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Partial trace relations beyond normal matrices

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arxiv 2507.18278 v1 pith:6S5DXSMG submitted 2025-07-24 quant-ph math-phmath.MP

classification quant-phmath-phmath.MP
keywords dilationsmatricespartialgeneralranktracetracesadmits
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abstract

We investigate the relationship between partial traces and their dilations for general complex matrices, focusing on two main aspects: the existence of (joint) dilations and norm inequalities relating partial traces and their dilations. Throughout our analysis, we pay particular attention to rank constraints. We find that every pair of matrices of equal size and trace admits dilations of any rank larger than one. We generalize Audenaert's subadditivity inequality to encompass general matrices, multiple tensor factors, and different norms. A central ingredient for this is a novel majorization relation for Kronecker sums. As an application, we extend the interval of Werner states in which they are provably 2-undistillable in any dimension $d\geq4$. We also prove new Schmidt-number witnesses and $k$-positive maps.

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Cited by 3 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. A solution to 2-copy distillability of Werner states

    quant-ph 2026-07 accept novelty 8.0 of 10

    Werner states are 2-copy distillable if and only if they are 1-copy distillable, for every local dimension.

  2. Two-copy nondistillability of Werner states: sharp partial-trace inequalities and finite-copy extensions

    quant-ph 2026-07 accept novelty 7.0 of 10

    Werner states ρ_α are two-copy distillable if and only if α < −1/2, via a sharp dimension-free rank-two partial-trace inequality.

  3. On the two-copy distillability of Werner states and a new partial trace inequality

    quant-ph 2026-07 accept novelty 7.0 of 10

    Werner states ρ(d,α) are two-copy undistillable exactly when α≥−1/2, so ρ(4,−1/2) is not two-copy distillable.

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