Quantum entanglement and quantum nonlocality for N-photon entangled states

摘要

Quantum entanglement and quantum nonlocality of N-photon entangled states vertical bar psi N-m > = C-m[cos gamma vertical bar N - m >(1)vertical bar m >(2) + e(i theta m) sin gamma vertical bar m >(1)vertical bar N - m >(2)] and their superpositions are studied. We point out that the relative phase theta(m) affects the quantum nonlocality but not the quantum entanglement for the state vertical bar psi N-m >. We show that quantum nonlocality can be controlled and manipulated by adjusting the state parameters of vertical bar psi N-m >, superposition coefficients, and the azimuthal angles of the Bell operator. We also show that the violation of the Bell inequality can reach its maximal value under certain conditions. It is found that quantum superpositions based on vertical bar psi N-m > can increase the amount of entanglement, and give more ways to reach the maximal violation of the Bell inequality.