AI 中文总结
该研究针对量子信息领域，给出了绝对正部分转置（APPT）二体态纯度的上界，且该上界在量子比特-准比特系统中为对应态的最大纯度。
AI 中文摘要
若量子态在任意整体幺正变换下仍保持可分（或正部分转置），则称其为绝对可分（或绝对正部分转置，APPT）态。已知所有绝对可分态的集合是所有APPT态集合的子集，且对量子比特-准比特系统，这两个集合完全相同。本文给出二体APPT态纯度的一个上界（因此也适用于绝对可分二体态的纯度）；对量子比特-准比特系统，该上界即为APPT（及绝对可分）态的最大纯度。
英文摘要
A quantum state is called absolutely separable (resp. absolutely positive partial transpose (APPT)) if it remains separable (resp. positive partial transpose (PPT)) under any global unitary transformation. It is known that the set of all absolutely separable states is a subset of the set of all APPT states. Moreover, these two sets are identical for qubit-qudit systems. In this note, we give an upper bound for the purity of APPT bipartite states (and therefore for the purity of absolutely separable bipartite states). For qubit-qudit systems, this upper bound becomes the maximum purity of APPT (and absolutely separable) states.
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