Quantifying entanglement of a two-qubit system via measurable and invariant moments of its partially transposed density matrix

被引:27
作者
Bartkiewicz, Karol [1 ,2 ,3 ]
Beran, Jiri [2 ,3 ]
Lemr, Karel [2 ,3 ]
Norek, Michal [1 ]
Miranowicz, Adam [1 ]
机构
[1] Adam Mickiewicz Univ, Fac Phys, PL-61614 Poznan, Poland
[2] Palacky Univ, Joint Lab Opt, RCPTM, Olomouc 77207, Czech Republic
[3] Acad Sci Czech Republ, Inst Phys, Olomouc 77207, Czech Republic
来源
PHYSICAL REVIEW A | 2015年 / 91卷 / 02期
关键词
MIXED STATES; QUANTUM; SEPARABILITY; PURIFICATION;
D O I
10.1103/PhysRevA.91.022323
中图分类号
O43 [光学];
学科分类号
070207 ; 0803 ;
摘要
We describe a direct method to determine the negativity of an arbitrary two-qubit state in experiments. The method is derived by analyzing the relation between the purity, negativity, and a universal entanglement witness for two-qubit entanglement. We show how the negativity of a two-qubit state can be calculated from just three experimentally accessible moments of the partially transposed density matrix of a two-photon state. Moreover, we show that the negativity can be given as a function of only six invariants, which are linear combinations of nine invariants from the complete set of 21 fundamental and independent two-qubit invariants. We analyze the relation between these moments and the concurrence for some classes of two-qubit states (including the X states, as well as pure states affected by the amplitude-damping and phase-damping channels). We also discuss the possibility of using the universal entanglement witness as an entanglement measure for various classes of two-qubit states. Moreover, we analyze how noise affects the estimation of entanglement via this witness.
引用
收藏
页数:10
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