PPT states of almost maximal Schmidt number

Abstract:We construct PPT states on $\mathbb{C}^m \otimes\mathbb{C}^n$ that have Schmidt number asymptotically approaching the smaller local dimension. More specifically, we construct a PPT state with Schmidt number at least $$ \left\lceil \frac{m + n - ((m - n)^2 + 4(m + n - 1))^{1/2}}{2} \right\rceil. $$ In the case of equal local dimensions ($m = n$), this becomes $n - \lfloor(2n - 1)^{1/2}\rfloor$, far exceeding the previous constructions which achieved $n/2 + O(1)$. In the case of unequal local dimensions, our result shows that there exists a PPT state on $\mathbb{C}^n \otimes \mathbb{C}^{3n-4}$ with Schmidt number at least $n-1$.

arXiv:2609.11849 [quant-ph]

(or arXiv:2609.11849v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2609.11849 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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