Physical systems have some degree of disorder present in them. We discuss how to treat natural, thermal entanglement in any random macroscopic system from which a thermodynamic witness bounded by a constant can be found. We propose that functional many-body perturbation theory be applied to allow either a quenched or an annealed average over the disorder to be taken. We find, when considering t...

The entanglement at finite temperatures are analyzed by using thermal models for colored quarks making up the hadron physical states. We have found that these quantum correlations entirely vanishes at Tc ≥ mq/ ln(1.5). For temperatures larger than Tc the correlations are classical. Also we worked out the entanglement for the transverse Ising spin chain. In dependence on both temperature T and t...

(Dated: March 12, 2004) The feasibility of creating molecular quantum entanglement in functionalized semiconductor nanostructures is computationally demonstrated. Entangled hole states, localized deep in the semiconductor band gap, are generated by electron-hole pair separation after photoexcitation of molecular surface complexes. The approach is illustrated for model arrays of catechol molecul...

The ground and thermal states of a quadratic hamiltonian representing the interaction of bosonic modes or particles are always Gaussian states. We investigate the entanglement properties of these states for the case where the interactions are represented by harmonic forces acting along the edges of symmetric graphs, i.e. 1, 2, and 3 dimensional rectangular lattices, mean field clusters and plat...

We investigate the entanglement dynamics between two dipole-coupled qubits interacting with vacuum or thermal fields of lossless resonators. Double Jaynes-Cummings model and two-atom Jaynes-Cummings model are considered taking into account detuning and direct dipole-dipole interaction. Using the dressed-states technique we derive the exact solutions for models under consideration. The computer ...

The radiation pressure of two laser beams detuned from resonance in an optical cavity can create a stable optical trap for a mechanical oscillation mode of a movable cavity mirror. Here it is shown that such a configuration entangles the output light fields via interaction with a mirror that is suspended as a pendulum. The degree of entanglement is quantified spectrally using the logarithmic ne...

We review the properties of reduced density matrices for free fermionic or bosonic many-particle systems in their ground state. Their basic feature is that they have a thermal form and thus lead to a quasi-thermodynamic problem with a certain free-particle Hamiltonian. We discuss the derivation of this result, the character of the Hamiltonian and its eigenstates, the single-particle spectra and...

We construct entanglement witnesses using fundamental quantum operators of spin models which contain two-particle interactions and have a certain symmetry. By choosing the Hamiltonian as such an operator, our method can be used for detecting entanglement by energy measurement. We apply this method to the Heisenberg model in a cubic lattice with a magnetic field, the XY model and other familiar ...

We analyze the relation between the entanglement and spin-squeezing parameter in the two-atom Dicke model and identify the source of the discrepancy recently reported by Banerjee and Zhou et al that one can observe entanglement without spin squeezing. Our calculations demonstrate that there are two criteria for entanglement, one associated with the two-photon coherences that create two-photon e...

In a recent paper Dajka, et.al., [J. Phys. A 40, F879 (2007)] predicted that some composite systems can be entangled forever even if coupled with a thermal bath. We analyze the transient entanglement of a single-Cooper-pair box biased by a classical voltage and irradiated by a single-mode quantized field and find the unusual feature that the phase-damped cavity can lead to a long-lived entangle...