Abstract A sufficient and necessary criterion for separability of bipartite quantum states is presented. We construct a class of mixed states in 2k quantum systems and in 3k quantum systems, respectively and show that these states are separable if and only if they are positive partial transpositions.
Fund: Project supported by the National Natural Science Foundation of China (Grant Nos. 11101017 and 11275131), Beijing Natural Science Foundation Program, and the Scientific Research Key Program of Beijing Municipal Commission of Education (Grant No. KZ201210028032), and the Importation and Development of High-Caliber Talents Project of Beijing Municipal Institutions (Grant No. CIT&TCD201404067).
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