8,847 research outputs found
Sudden Death of Entanglement of Two Jaynes-Cummings Atoms
We investigate entanglement dynamics of two isolated atoms, each in its own
Jaynes-Cummings cavity. We show analytically that initial entanglement has an
interesting subsequent time evolution, including the so-called sudden death
effect.Comment: 3 pages, 3 figure
Elastodynamics of radially inhomogeneous spherically anisotropic elastic materials in the Stroh formalism
A method is presented for solving elastodynamic problems in radially
inhomogeneous elastic materials with spherical anisotropy, i.e.\ materials such
that in a spherical coordinate system
. The time harmonic displacement field is expanded in a separation of variables form with dependence on
described by vector spherical harmonics with -dependent
amplitudes. It is proved that such separation of variables solution is
generally possible only if the spherical anisotropy is restricted to transverse
isotropy with the principal axis in the radial direction, in which case the
amplitudes are determined by a first-order ordinary differential system.
Restricted forms of the displacement field, such as ,
admit this type of separation of variables solutions for certain lower material
symmetries. These results extend the Stroh formalism of elastodynamics in
rectangular and cylindrical systems to spherical coordinates.Comment: 15 page
Experimental observation of negative differential resistance from an InAs/GaSb interface
We have observed negative differential resistance at room temperature from devices consisting of a single interface between n-type InAs and p-type GaSb. InAs and GaSb have a type II staggered band alignment; hence, the negative differential resistance arises from the same mechanism as in a p+-n+ tunnel diode. Room-temperature peak current densities of 8.2×10^4 A/cm^2 and 4.2×10^4 A/cm^2 were measured for structures with and without undoped spacer layers at the heterointerface, respectively
Non-Markovian Quantum Trajectories of Many-Body Quantum Open Systems
A long-standing open problem in non-Markovian quantum state diffusion (QSD)
approach to open quantum systems is to establish the non-Markovian QSD
equations for multiple qubit systems. In this paper, we settle this important
question by explicitly constructing a set of exact time-local QSD equations for
-qubit systems. Our exact time-local (convolutionless) QSD equations have
paved the way towards simulating quantum dynamics of many-body open systems
interacting with a common bosonic environment. The applicability of this
multiple-qubit stochastic equation is exemplified by numerically solving
several quantum open many-body systems concerning quantum coherence dynamics
and dynamical control.Comment: 8 pages, 2 figures. manuscript revised and reference update
Dislocation core field. I. Modeling in anisotropic linear elasticity theory
Aside from the Volterra field, dislocations create a core field, which can be
modeled in linear anisotropic elasticity theory with force and dislocation
dipoles. We derive an expression of the elastic energy of a dislocation taking
full account of its core field and show that no cross term exists between the
Volterra and the core fields. We also obtain the contribution of the core field
to the dislocation interaction energy with an external stress, thus showing
that dislocation can interact with a pressure. The additional force that
derives from this core field contribution is proportional to the gradient of
the applied stress. Such a supplementary force on dislocations may be important
in high stress gradient regions, such as close to a crack tip or in a
dislocation pile-up
Structural instability associated with the tilting of CuO6 octahedra in La2-xSrxCuO4
Comprehensive inelastic neutron-scattering measurements were performed to
study the soft optical phonons in La2-xSrxCuO4 at x=0.10, 0.12 and 0.18. We
found at x=0.18 that the softening of Z-point phonon, suggesting incipient
structural transition from the low-temperature orthorhombic (LTO) to
low-temperature tetragonal (LTT) phase, breaks at Tc, which is consistent with
the previous report by Lee et al. for the optimally doped x=0.15 sample. As for
x=0.10 and 0.12, on the other hand, the softening continues even below Tc. It
is thus clarified that the breaking of soft phonon is characteristic of
La2-xSrxCuO4 in the optimally and overdoped regions. In the course of studying
the soft phonons, we discovered that a central peak remains above the LTO to
high-temperature tetragonal (HTT) phase transition at Ts1 and splits into
incommensurate components along the (1 1 0)HTT direction at higher
temperatures. This is a common feature for both x=0.12 and 0.18 and their
temperature dependences of the splitting 2d can be scaled by using a
renormalized temperature T/Ts1. In the high temperature limit, d saturates
around d ~ 0.12 r.l.u., which value is close to the splitting of incommensurate
magnetic signals. This implies that the incipient lattice modulation starts
appearing at very high temperature. Details of this modulation and its
relations with other properties are, however, not yet clarified.Comment: 7 pages, 5 eps figure
Soft phonons and structural phase transitions in LaBaCuO
Soft phonon behavior associated with a structural phase transition from the
low-temperature-orthorhombic (LTO) phase ( symmetry) to the
low-temperature-tetragonal (LTT) phase ( symmetry) was investigated
in LaBaCuO using neutron scattering. As temperature
decreases, the TO-mode at -point softens and approaches to zero energy
around K, where the LTO -- LTT transition occurs. Below , the phonon hardens quite rapidly and it's energy almost saturates below
50 K. At , the energy dispersion of the soft phonon along in-plane
direction significantly changes while the dispersion along out-of-plane
direction is almost temperature independent. Coexistence between the LTO phase
and the LTT phase, seen in both the soft phonon spectra and the peak profiles
of Bragg reflection, is discussed in context of the order of structural phase
transitions.Comment: 6 pages, 8 figure
A note on Zolotarev optimal rational approximation for the overlap Dirac operator
We discuss the salient features of Zolotarev optimal rational approximation
for the inverse square root function, in particular, for its applications in
lattice QCD with overlap Dirac quark. The theoretical error bound for the
matrix-vector multiplication is derived. We check that
the error bound is always satisfied amply, for any QCD gauge configurations we
have tested. An empirical formula for the error bound is determined, together
with its numerical values (by evaluating elliptic functions) listed in Table 2
as well as plotted in Figure 3. Our results suggest that with Zolotarev
approximation to , one can practically preserve the exact
chiral symmetry of the overlap Dirac operator to very high precision, for any
gauge configurations on a finite lattice.Comment: 23 pages, 5 eps figures, v2:minor clarifications, and references
added, to appear in Phys. Rev.
Modeling of Indoor Wave Propagation Models from 1 G Hz to 10 G Hz
This paper presents the modeling of indoor wave propagation from 1 GHz to 10 GHz. Several obstacles such as partition, whiteboard, and door have been tested and measured their losses compare to line of sight. Horn antennas have been used as transmitter and receiver. An average attenuation between of this obstacle between 1.5 dB to 3.0 dB has been observed. Prediction model for this indoor propagation has been presented using suitable software. Finally, results, discussion, conclusions and further work are given
Entanglement sudden birth of two trapped ions interacting with a time-dependent laser field
We explore and develop the mathematics of the two multi-level ions. In
particular, we describe some new features of quantum entanglement in two
three-level trapped ions confined in a one-dimensional harmonic potential,
allowing the instantaneous position of the center-of-mass motion of the ions to
be explicitly time-dependent. By solving the exact dynamics of the system, we
show how survivability of the quantum entanglement is determined by a specific
choice of the initial state settings.Comment: 13 pages, 4 figure
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