7,775 research outputs found
The entanglement dynamics of interacting qubits embedded in a spin environment with Dzyaloshinsky-Moriya term
We investigate the entanglement dynamics of two interacting qubits in a spin
environment, which is described by an XY model with Dzyaloshinsky-Moriya (DM)
interaction. The competing effects of environmental noise and interqubit
coupling on entanglement generation for various system parameters are studied.
We find that the entanglement generation is suppressed remarkably in
weak-coupling region at quantum critical point (QCP). However, the suppression
of the entanglement generation at QCP can be compensated both by increasing the
DM interaction and by decreasing the anisotropy of the spin chain. Beyond the
weak-coupling region, there exist resonance peaks of concurrence when the
system-bath coupling equals to external magnetic field. We attribute the
presence of resonance peaks to the flat band of the self-Hamiltonian. These
peaks are highly sensitive to anisotropy parameter and DM interaction.Comment: 8 pages, 9 figure
Quantum phase transitions in exactly solvable one-dimensional compass models
We present an exact solution for a class of one-dimensional compass models
which stand for interacting orbital degrees of freedom in a Mott insulator. By
employing the Jordan-Wigner transformation we map these models on
noninteracting fermions and discuss how spin correlations, high degeneracy of
the ground state, and symmetry in the quantum compass model are visible
in the fermionic language. Considering a zigzag chain of ions with singly
occupied orbitals ( orbital model) we demonstrate that the orbital
excitations change qualitatively with increasing transverse field, and that the
excitation gap closes at the quantum phase transition to a polarized state.
This phase transition disappears in the quantum compass model with maximally
frustrated orbital interactions which resembles the Kitaev model. Here we find
that finite transverse field destabilizes the orbital-liquid ground state with
macroscopic degeneracy, and leads to peculiar behavior of the specific heat and
orbital susceptibility at finite temperature. We show that the entropy and the
cooling rate at finite temperature exhibit quite different behavior near the
critical point for these two models.Comment: 15 pages, 14 figure
Enhancement of quantum correlations between two particles under decoherence in finite temperature environment
Enhancing the quantum correlations in realistic quantum systems interacting
with the environment of finite temperature is an important subject in quantum
information processing. In this paper, we use weak measurement and measurement
reversal to enhance the quantum correlations in a quantum system consisting of
two particles. The transitions of the quantum correlations measured by the
local quantum uncertainty of qubit-qubit and qutrit-qutrit quantum systems
under generalized amplitude damping channels are investigated. We show that,
after the weak measurement and measurement reversal, the joint system shows
more robustness against decoherence.Comment: 5 pages, 5 figure
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