Entanglement and squeezing of multi-qubit systems using a two-axis countertwisting Hamiltonian with an external field

We study the squeezing and pairwise entanglement properties of multi-qubit spin systems, implemented by a two-axis countertwisting Hamiltonian, with and without an external field. We show that the addition of an external field, enforces stronger squeezing and entanglement, and also increases the time duration that these phenomena may be maintained.     

A new approach for radon monitoring in soil as an earthquake precursor using optical fiber

Temporal variations of radon concentration in soil before the earthquake are known as an earthquake precursor. For using of radon as an earthquake precursor, it is necessary to constantly monitor radon concentration variations in a relatively wide range in the vicinity of a fault which is virtually impossible for radon detectors that already exist. This paper proposes a new method for continuous measurement of radon concentration variations in a wide range, using optical fiber as radon detector. For this purpose, an experimental system consisting of radon source, optical-fiber holding chamber, radon gas detector, optical laser source, and optical power meter have been arranged to with the aim to create different concentrations of radon gas in the vicinity of the optical fiber; the attenuation which creates on optical fiber is subsequently measured. As a result, the average of the attenuation is 0.004 μw per each meter per Bq/l since the fault’s length is more than ten kilometers; sensitivity of the measurement can be improved many times over.     

Correlations for a Family of Two-Ququart Quantum States

In this paper, a quantum correlations analytical treatment for a family of two-ququart states are presented. For this purpose, a family of two-ququart quantum states, as well as a set of von Neumann measurements are proposed. A quantum discord analytical treatment is derived for this family of two-ququart states. Finally, the classical mutual information, the entanglement of formation and quantum discord are illustrated in this family of two-ququart quantum states.

     

Efficient Entanglement Measure for Graph States

International Journal of Theoretical Physics - In this paper, we study the multipartite entanglement properties of graph states up to seven qubits. Our analysis shows that the generalized...     

Thermal Entanglement Properties in Two Qubits One-Axis Spin Squeezing Model with an External Magnetic Field

In a recent article in this journal Guo-Hui (Int. J. Theor. Phys. 56, 600, 2017) has investigated the quantum correlation properties in the two qubits one-axis spin squeezing model with an external magnetic field by means of concurrence (C) and quantum discord (QD) criteria. We are to reveal numerically and analytically that in the limiting case T→ 0 (ground state) the sudden disappearance phenomenon (SDP) does not occur in the behavior of C and the values obtained for C are incorrect.