Entanglement versus energy in quantum spin models

Abstract We study entanglement properties of all eigenstates of the Heisenberg XXX model, and find that the entanglement and mixedness for a pair of nearest-neighbor qubits are completely determined by the corresponding eigenenergies. Specifically, the negativity of the eigenenergy implies pairwise entanglement. From the relation between entanglement and eigenenergy, we obtain finite-size behaviors of the entanglement. We also study entanglement and mixedness versus energy in the quantum Heisenberg XY model. Quantum entanglement lies at the heart of quantum mechanics, and can be exploited to accomplish some physical tasks such as quantum teleportation Recently, the study of entanglement properties in many-body systems have received much attention where C refers to the concurrence for two nearestneighbor qubits, and E 0 is the ground-state energy. For a pair of qubits, the entanglement of formation can be obtained from the concurrence C where h(x) = −x log 2 x − (1 − x) log 2 (1 − x). The concurrence itself is a good measure of two-qubit entanglement, and we adopt it as our measure of pairwise entanglement. 0375-9601/$ -see front matte