## The Magic Power of the $π/8$ Gate in a Two-Qubit System    [PDF]

Zhe Guan, Huan He, Yong-Jian Han, Chuan-Feng Li, Guang-Can Guo
Fernando Galve \emph{et al.} $[Phy. Rev. Lett. \textbf{110}, 010501 (2013)]$ introduced discording power for a two-qubit unitary gate to evaluate its capability to produce quantum discord , and found that a $\pi/8$ gate has maximal discording power. This work analyzes the entangling power of a two-qubit unitary gate, which reflects its ability to generate quantum entanglement in another way. Based on the renowned Cartan decomposition of two-qubit unitary gates, we show that the magic power of the $\pi/8$ gate produces maximal entanglement for a general value of purities for two-qubit states.
View original: http://arxiv.org/abs/1306.1443