The two-body thermal entanglement and mixture in a three-spin spin chain in thermal equilibrium state are investigated, and the effects of the temperature and magnetic field on the entanglement and mixture are discussed. It is found that, in the ground state, an important class of states, i.e., maximally entangled mixed states, can be generated by controlling magnetic field, which provide a new way to generate maximally entangled mixed states and control entanglement. Further, the spin chain in the thermal equilibrium is used as a quantum channel for quantum communication. The effects of temperature and magnetic field on fidelity are discussed. It is shown that the temperature and magnetic field have vast effects on the fidelity. The relation between fidelity and two-body thermal entanglement is given, which shows that more amount of entanglement does not means higher fidelity.The two-body thermal entanglement and mixture in a three-spin spin chain in thermal equilibrium state are investigated, and the effects of the temperature and magnetic field on the entanglement and mixture are discussed. It is found that, in the ground state, an important class of states, i.e., maximally entangled mixed states, can be generated by controlling magnetic field, which provide a new way to generate maximally entangled mixed states and control entanglement. Further, the spin chain in the thermal equilibrium is used as a quantum channel for quantum communication. The effects of temperature and magnetic field on fidelity are discussed. It is shown that the temperature and magnetic field have vast effects on the fidelity. The relation between fidelity and two-body thermal entanglement is given, which shows that more amount of entanglement does not means higher fidelity.

Chinese Journal of Quantum ElectronicsJan 1, 20100 citations

Entanglement in quantum spin systems

Jeffrey Scott Pratt

Jan 1, 20050 citations

Entanglement and quantum phase transitions in quantum mixed spin chains

Shangbin Li, Zhaoxin Xu, Jianhui Dai +1 more

The ground entanglement and thermal entanglement in quantum mixed spin chains consisting of two integer spins 1 and two half-integer spins $\frac{1}{2}$ arrayed as $\frac{1}{2}\text{\ensuremath{-}}\frac{1}{2}\text{\ensuremath{-}}1\text{\ensuremath{-}}1$ in a unit cell with antiferromagnetic nearest-neighbor couplings ${J}_{1}$ $({J}_{2})$ between the spins of equal (different) magnitudes are investigated by employing the logarithmic negativity as entanglement measure. The ground entanglement transition found here is closely related to the valence-bond-solid phase transition, and the thermal entanglement near the critical point is calculated and it is shown that two distinct behaviors exist in the nearest-neighbor same kind of spins and different kind of spins, respectively.The ground entanglement and thermal entanglement in quantum mixed spin chains consisting of two integer spins 1 and two half-integer spins $\frac{1}{2}$ arrayed as $\frac{1}{2}\text{\ensuremath{-}}\frac{1}{2}\text{\ensuremath{-}}1\text{\ensuremath{-}}1$ in a unit cell with antiferromagnetic nearest-neighbor couplings ${J}_{1}$ $({J}_{2})$ between the spins of equal (different) magnitudes are investigated by employing the logarithmic negativity as entanglement measure. The ground entanglement transition found here is closely related to the valence-bond-solid phase transition, and the thermal entanglement near the critical point is calculated and it is shown that two distinct behaviors exist in the nearest-neighbor same kind of spins and different kind of spins, respectively.

arXiv:quant-ph/0508115Physical Review BMay 10, 200616 citations

Thermal Entanglement in Disordered Spin Chains: Localization, Thresholds, and the Quantum-to-Classical Crossover

Sun, Dihang, Zhigang Hu, Biao Wu

We investigate the mixed-state entanglement between two spins embedded in the XXZ Heisenberg chain under thermal equilibrium. By deriving an analytical expression for the entanglement of two-spin thermal states and extending this analysis to larger spin chains, we demonstrate that mixed-state entanglement is profoundly shaped by both disorder and temperature. Our results reveal a sharp distinction between many-body localized (MBL) and ergodic phases, with entanglement vanishing above different finite temperature thresholds. Furthermore, by analyzing non-adjacent spins, we uncover an approximate exponential decay of entanglement with separation. This work advances the understanding of the quantum-to-classical transition by linking the entanglement properties of small subsystems to the broader thermal environment, offering a explanation for the absence of entanglement in macroscopic systems. These findings provide critical insights into quantum many-body physics, bridging concepts from thermalization, localization, and quantum information theory.We investigate the mixed-state entanglement between two spins embedded in the XXZ Heisenberg chain under thermal equilibrium. By deriving an analytical expression for the entanglement of two-spin thermal states and extending this analysis to larger spin chains, we demonstrate that mixed-state entanglement is profoundly shaped by both disorder and temperature. Our results reveal a sharp distinction between many-body localized (MBL) and ergodic phases, with entanglement vanishing above different finite temperature thresholds. Furthermore, by analyzing non-adjacent spins, we uncover an approximate exponential decay of entanglement with separation. This work advances the understanding of the quantum-to-classical transition by linking the entanglement properties of small subsystems to the broader thermal environment, offering a explanation for the absence of entanglement in macroscopic systems. These findings provide critical insights into quantum many-body physics, bridging concepts from thermalization, localization, and quantum information theory.

arXiv:2502.19464Feb 26, 20250 citations

The ground entanglement and thermal entanglement in quantum mixed spin chains consisting of two integer spins 1 and two half-integer spins

\frac{1}{2}

arrayed as $\frac{1}{2}\text{\ensuremath{-}}\frac{1}{2}\text{\ensuremath{-}}1\text{\ensuremath{-}}1$ in a unit cell with antiferromagnetic nearest-neighbor couplings

{J}_{1}

({J}_{2})

between the spins of equal (different) magnitudes are investigated by employing the logarithmic negativity as entanglement measure. The ground entanglement transition found here is closely related to the valence-bond-solid phase transition, and the thermal entanglement near the critical point is calculated and it is shown that two distinct behaviors exist in the nearest-neighbor same kind of spins and different kind of spins, respectively.