Stability of global entanglement in thermal states of spin chains
arXiv:quant-ph/0406064 · doi:10.1103/PhysRevA.70.052303
Abstract
We investigate the entanglement properties of a one dimensional chain of spin qubits coupled via nearest neighbor interactions. The entanglement measure used is the n-concurrence, which is distinct from other measures on spin chains such as bipartite entanglement in that it can quantify "global" entanglement across the spin chain. Specifically, it computes the overlap of a quantum state with its time-reversed state. As such this measure is well suited to study ground states of spin chain Hamiltonians that are intrinsically time reversal symmetric. We study the robustness of n-concurrence of ground states when the interaction is subject to a time reversal antisymmetric magnetic field perturbation. The n-concurrence in the ground state of the isotropic XX model is computed and it is shown that there is a critical magnetic field strength at which the entanglement experiences a jump discontinuity from the maximum value to zero. The n-concurrence for thermal mixed states is derived and a threshold temperature is computed below which the system has non zero entanglement.
arXiv comment13 pages, 3 figures. v.2 includes minor corrections and an added section treating the quantum XX model with open boundaries
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- Entanglement versus energy in quantum spin models
- Multi-quantum eigenstates of a linear chain of coupled qubits
- Thermalization through unitary evolution of pure states
- Entanglement oscillations in open Heisenberg chains
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