Genuine entanglement of four-qubit cluster diagonal states
Xiaoyu Chen, Ping Yu, Li-zhen Jiang, Mingzhen Tian · Physical Review A · 2013
We reduce the necessary and sufficient biseparable conditions of four-qubit cluster diagonal states to concise forms. Only 4 out of the 15 parameters are proved to be relevant in specifying the genuine entanglement of the states. Using the relative entropy of entanglement as entanglement measure, we analytically find the genuine entanglement of all the four-qubit cluster diagonal states. The formulas for the genuine entanglement are of five kinds, for seven different parameter regions of genuinely entangled states.