Entanglement monogamy of tripartite quantum states

An interesting monogamy equation with the form of the Pythagorean theorem is found for 2 circle times 2 circle times n-dimensional pure states, which reveals the relation among bipartite concurrence, concurrence of assistance, and genuine tripartite entanglement. At the same time, a genuine tripartite entanglement monotone as a generalization of 3-tangle is naturally obtained for (2 circle times 2 circle times n)-dimensional pure states in terms of a distinct idea. For mixed states, the monogamy equation is reduced to a monogamy inequality. Both results for tripartite quantum states can be employed to multipartite quantum states.