Łukasz Rudnicki, Zbigniew Puchała, Paweł Horodecki, Karol Życzkowski
Bounds analogous to entropic uncertainty relations allow one to design practical tests to detect quantum entanglement by a collective measurement performed on several copies of the state analyzed. This approach, initially worked out for pure states only [Phys. Rev. Lett. 107, 150502 (2011)], is extended here for mixed quantum states. We define collectibility for any mixed states of a multipartite system. Deriving bounds for collectibility for positive partially transposed states of given purity provides a new insight into the structure of entangled quantum states. In case of two qubits the application of complementary measurements and coincidence based detections leads to a new test of entanglement of pseudopure states.
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http://arxiv.org/abs/1211.0573
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