149,877 research outputs found
Probing spin entanglement by gate-voltage-controlled interference of current correlation in quantum spin Hall insulators
We propose an entanglement detector composed of two quantum spin Hall
insulators and a side gate deposited on one of the edge channels. For an ac
gate voltage, the differential noise contributed from the entangled electron
pairs exhibits the nontrivial step structures, from which the spin entanglement
concurrence can be easily obtained. The possible spin dephasing effects in the
quantum spin Hall insulators are also included.Comment: Physics Letters A in pres
Diagnostics of macroscopic quantum states of Bose-Einstein condensate in double-well potential by nonstationary Josephson effect
We propose a method of diagnostic of a degenerate ground state of Bose
condensate in a double well potential. The method is based on the study of the
one-particle coherent tunneling under switching the time-dependent weak
Josephson coupling between the wells. We obtain a simple expression that allows
to determine the phase of the condensate and the total number of the particles
in the condensate from the relative number of the particles in two wells
measured before the Josephson coupling is switched on and
after it is switched off. The specifics of the application of the method in the
cases of the external and the internal Josephson effect are discussed.Comment: 3 page
Exploring Quantum Phase Transitions with a Novel Sublattice Entanglement Scenario
We introduce a new measure called reduced entropy of sublattice to quantify
entanglement in spin, electron and boson systems. By analyzing this quantity,
we reveal an intriguing connection between quantum entanglement and quantum
phase transitions in various strongly correlated systems: the local extremes of
reduced entropy and its first derivative as functions of the coupling constant
coincide respectively with the first and second order transition points. Exact
numerical studies merely for small lattices reproduce several well-known
results, demonstrating that our scenario is quite promising for exploring
quantum phase transitions.Comment: 4 pages, 4 figure
Expanded mixed multiscale finite element methods and their applications for flows in porous media
We develop a family of expanded mixed Multiscale Finite Element Methods
(MsFEMs) and their hybridizations for second-order elliptic equations. This
formulation expands the standard mixed Multiscale Finite Element formulation in
the sense that four unknowns (hybrid formulation) are solved simultaneously:
pressure, gradient of pressure, velocity and Lagrange multipliers. We use
multiscale basis functions for the both velocity and gradient of pressure. In
the expanded mixed MsFEM framework, we consider both cases of separable-scale
and non-separable spatial scales. We specifically analyze the methods in three
categories: periodic separable scales, - convergence separable scales, and
continuum scales. When there is no scale separation, using some global
information can improve accuracy for the expanded mixed MsFEMs. We present
rigorous convergence analysis for expanded mixed MsFEMs. The analysis includes
both conforming and nonconforming expanded mixed MsFEM. Numerical results are
presented for various multiscale models and flows in porous media with shales
to illustrate the efficiency of the expanded mixed MsFEMs.Comment: 33 page
- …