Optimized generalized monogamy relations and upper bounds for N-qubit systems

We present optimized generalized monogamy relations and upper bounds derived from concurrence and concurrence of assistance. We first establish a tighter general upper bound of the α th ( 0 ⩽ α ⩽ 2 ) power of concurrence for N -qubit states. Then for N -qubit systems A B C 1 … C N − 2 , the optimized monogamy relations and upper bounds satisfied by the α th ( 0 ⩽ α ⩽ 2 ) power of concurrence of N -qubit pure states under the partition AB and C 1 … C N − 2 , as well as under the partition ABC 1 and C 2 … C N − 2 are established, which give rise to restrictions on the entanglement distribution and trade offs among the subsystems. Moreover, the utilization of the W -class states demonstrates that our results are tighter compared with the existing results. Similar results are also obtained for negativity.