39,905 research outputs found
Spontaneous spin textures in dipolar spinor condensates
We have mapped out a detailed phase diagram that shows the ground state
structure of a spin-1 condensate with magnetic dipole-dipole interactions. We
show that the interplay between the dipolar and the spin-exchange interactions
induces a rich variety of quantum phases that exhibit spontaneous magnetic
ordering in the form of intricate spin textures.Comment: 4.1 pages, 4 figure
Mixed Qubit Cannot Be Universally Broadcast
We show that there does not exist any universal quantum cloning machine that
can broadcast an arbitrary mixed qubit with a constant fidelity. Based on this
result, we investigate the dependent quantum cloner in the sense that some
parameter of the input qubit is regarded as
constant in the fidelity. For the case of constant , we establish the
optimal symmetric dependent cloner with a fidelity 1/2. It is also
shown that the optimal quantum cloning machine for pure qubits is also
optimal for mixed qubits, when is the unique parameter in the
fidelity. For general broadcasting of mixed qubits, the situation is
very different.Comment: 5 pages, Revte
Simultaneous eigenstates of the number-difference operator and a bilinear interaction Hamiltonian derived by solving a complex differential equation
As a continuum work of Bhaumik et al who derived the common eigenvector of
the number-difference operator Q and pair-annihilation operator ab (J. Phys. A9
(1976) 1507) we search for the simultaneous eigenvector of Q and
(ab-a^{+}b^{+}) by setting up a complex differential equation in the bipartite
entangled state representation. The differential equation is then solved in
terms of the two-variable Hermite polynomials and the formal hypergeometric
functions. The work is also an addendum to Mod. Phys. Lett. A 9 (1994) 1291 by
Fan and Klauder, in which the common eigenkets of Q and pair creators are
discussed
Time-resolved measurement of single pulse femtosecond laser-induced periodic surface structure formation
Time-resolved diffraction microscopy technique has been used to observe the
formation of laser-induced periodic surface structures (LIPSS) from the
interaction of a single femtosecond laser pulse (pump) with a nano-scale groove
mechanically formed on a single-crystal Cu substrate. The interaction dynamics
(0-1200 ps) was captured by diffracting a time-delayed, frequency-doubled pulse
from nascent LIPSS formation induced by the pump with an infinity-conjugate
microscopy setup. The LIPSS ripples are observed to form sequentially outward
from the groove edge, with the first one forming after 50 ps. A 1-D analytical
model of electron heating and surface plasmon polariton (SPP) excitation
induced by the interaction of incoming laser pulse with the groove edge
qualitatively explains the time-evloution of LIPSS formation.Comment: 4 pages, 5 figure
Suppression of ferromagnetic ordering in doped manganites: Effects of the superexchange interaction
From a Monte Carlo study of the ferromagnetic Kondo lattice model for doped
manganites, including the antiferromagnetic superexchange interaction
(), we found that the ferromagnetic ordering was suppressed as
increased. The ferromagnetic transition temperature , as obtained from a
mean field fit to the calculated susceptibilities, was found to decrease
monotonically with increasing . Further, the suppression in
scales with the bandwidth narrowing induced by the antiferromagnetic
frustration originating from . From these results, we propose that the
change in the superexchange interaction strength between the electrons
of the Mn ions is one of the mechanisms responsible for the suppression in
observed in manganites of the type
(LaPr)CaMnO.Comment: 5 pages, 6 figures. To appear in PR
Energy average formula of photon gas rederived by using the generalized Hermann-Feynman theorem
By virtue of the generalized Hermann-Feynmam theorem and the method of
characteristics we rederive energy average formula of photon gas, this is
another useful application of the theorem.Comment: 2 page
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