Entanglement monogamy in a three-qubit state

We investigate the monogamy nature of entanglement in a three-qubit system. A monogamy inequality is presented to describe the exclusive relation between the A-B two-qubit concurrence CAB and the AB-C three-qubit concurrence C (AB) C, which represents the entanglement between qubits A and B as a whole and the third qubit C. It is found that the entanglement between any two qubits in a three-qubit system is limited by the entanglement between these two qubits and another qubit. As a consequence, we present the upper bounds for the concurrence CAB, when the concurrence between qubits A and C (CAC) and the concurrence between qubits B and C (CBC) are both given or one of the two is provided.