3,612 research outputs found
Quantum Energy Teleportation with Electromagnetic Field: Discrete vs. Continuous Variables
It is well known that usual quantum teleportation protocols cannot transport
energy. Recently, new protocols called quantum energy teleportation (QET) have
been proposed, which transport energy by local operations and classical
communication with the ground states of many-body quantum systems. In this
paper, we compare two different QET protocols for transporting energy with
electromagnetic field. In the first protocol, a 1/2 spin (a qubit) is coupled
with the quantum fluctuation in the vacuum state and measured in order to
obtain one-bit information about the fluctuation for the teleportation. In the
second protocol, a harmonic oscillator is coupled with the fluctuation and
measured in order to obtain continuous-variable information about the
fluctuation. In the spin protocol, the amount of teleported energy is
suppressed by an exponential damping factor when the amount of input energy
increases. This suppression factor becomes power damping in the case of the
harmonic oscillator protocol. Therefore, it is concluded that obtaining more
information about the quantum fluctuation leads to teleporting more energy.
This result suggests a profound relationship between energy and quantum
information.Comment: 24 pages, 4 figures, to be published in Journal of Physics A:
Mathematical and Theoretica
Filling dependence of a new type of charge ordered liquid on a triangular lattice system
We study the recently reported characteristic gapless charge ordered state in
a spinless fermion system on a triangular lattice under strong inter-site
Coulomb interactions. In this state the charges are spontaneously divided into
solid and liquid component, and the former solid part aligns in a Wigner
crystal manner while the latter moves among them like a pinball. We show that
such charge ordered liquid is stable over a wide range of filling, ,
and examine its filling dependent nature.Comment: 3 pages 3 figure
Dynamic Soft Elasticity in Monodomain Nematic Elastomers
We study the linear dynamic mechanical response of monodomain nematic liquid
crystalline elastomers under shear in the geometry that allows the director
rotation. The aspects of time-temperature superposition are discussed at some
length and Master Curves are obtained between the glassy state and the nematic
transition temperature Tni. However, the time-temperature superposition did not
work through the clearing point Tni, due to change from the ``soft-elasticity''
nematic regime to the ordinary isotropic rubber response. We focus on the
low-frequency region of the Master Curves and establish the power-law
dependence of the modulus G' ~ omega^a. This law agrees very well with the
results of static stress relaxation, where each relaxation curve obeys the
analogous power law G' ~ t^{-a} in the corresponding region of long times and
temperatures.Comment: Latex, [epj]{svjour} style, 9 pages 11 figures submitted to Euro.
Phys. J.
Microscopic analysis of multipole susceptibility of actinide dioxides: A scenario of multipole ordering in AmO
By evaluating multipole susceptibility of a seven-orbital impurity Anderson
model with the use of a numerical renormalization group method, we discuss
possible multipole states of actinide dioxides at low temperatures. In
particular, here we point out a possible scenario for multipole ordering in
americium dioxide. For Am ion with five electrons, it is considered
that the ground state is doublet and the first excited state is
quartet, but we remark that the ground state is easily
converted due to the competition between spin-orbit coupling and Coulomb
interactions. Then, we find that the quartet can be the ground
state of AmO even for the same crystalline electric field potential. In the
case of quartet ground state, the numerical results suggest that
high-order multipoles such as quadrupole and octupole can be relevant to
AmO.Comment: 8 pages, 4 figures. To appear in Phys. Rev.
Quadrupole Susceptibility of Gd-Based Filled Skutterudite Compounds
It is shown that quadrupole susceptibility can be detected in Gd compounds
contrary to our textbook knowledge that Gd ion induces pure spin moment
due to the Hund's rules in an coupling scheme. The ground-state multiplet
of Gd is always characterized by =7/2, where denotes total
angular momentum, but in a - coupling scheme, one electron in =7/2
octet carries quadrupole moment, while other six electrons fully occupy =5/2
sextet, where denotes one-electron total angular momentum. For realistic
values of Coulomb interaction and spin-orbit coupling, the ground-state
wavefunction is found to contain significant amount of the - coupling
component. From the evaluation of quadrupole susceptibility in a simple
mean-field approximation, we point out a possibility to detect the softening of
elastic constant in Gd-based filled skutterudites.Comment: 8 pages, 4 figure
Quantum Energy Teleportation with a Linear Harmonic Chain
A protocol of quantum energy teleportation is proposed for a one-dimensional
harmonic chain. A coherent-state POVM measurement is performed to coupled
oscillators of the chain in the ground state accompanied by energy infusion to
the system. This measurement consumes a part of ground state entanglement.
Depending on the measurement result, a displacement operation is performed on a
distant oscillator accompanied by energy extraction from the zero-point
fluctuation of the oscillator. We find that the amount of consumed entanglement
is bounded from below by a positive value that is proportional to the amount of
teleported energy.Comment: 23 pages, 10 figures, analysis for non-critical case is added,
accepted for publication in PR
Multipole correlations in low-dimensional f-electron systems
By using a density matrix renormalization group method, we investigate the
ground-state properties of a one-dimensional three-orbital Hubbard model on the
basis of a j-j coupling scheme. For , where is a parameter
to control cubic crystalline electric field effect, one orbital is itinerant,
while other two are localized. Due to the competition between itinerant and
localized natures, we obtain orbital ordering pattern which is sensitive to
, leading to a characteristic change of quadrupole state
into an incommensurate structure. At , all the three orbitals are
degenerate, but we observe a peak at in quadrupole
correlation, indicating a ferro-orbital state, and the peak at in
dipole correlation, suggesting an antiferromagnetic state. We
also discuss the effect of octupole on magnetic anisotropy.Comment: 4 pages, 3 figures, Proceedings of ASR-WYP-2005 (September 27-29,
2005, Tokai
Multipole as -Electron Spin-Charge Density in Filled Skutterudites
It is shown that -electron multipole is naturally defined as spin-charge
one-electron density operator in the second-quantized form with the use of
tensor operator on the analogy of multipole expansion of electromagnetic
potential from charge distribution in electromagnetism. Due to this definition
of multipole, it is possible to determine multipole state from a microscopic
viewpoint on the basis of the standard linear response theory for multipole
susceptibility. In order to discuss multipole properties of filled
skutterudites, we analyze a seven-orbital impurity Anderson model by employing
a numerical renormalization group method. We show our results on possible
multipole states of filled skutterudite compounds.Comment: To appear in the Proceedings of International Conference on "New
Quantum Phenomena in Skutterudite and Related Systems" (September 2007, Kobe,
Japan
Effective Crystalline Electric Field Potential in a j-j Coupling Scheme
We propose an effective model on the basis of a - coupling scheme to
describe local -electron states for realistic values of Coulomb interaction
and spin-orbit coupling , for future development of microscopic
theory of magnetism and superconductivity in -electron systems, where
is the number of local electrons. The effective model is systematically
constructed by including the effect of a crystalline electric field (CEF)
potential in the perturbation expansion in terms of . In this paper,
we collect all the terms up to the first order of . Solving the
effective model, we show the results of the CEF states for each case of
=25 with symmetry in comparison with those of the Stevens
Hamiltonian for the weak CEF. In particular, we carefully discuss the CEF
energy levels in an intermediate coupling region with in the order
of 0.1 corresponding to actual -electron materials between the and
- coupling schemes. Note that the relevant energy scale of is the
Hund's rule interaction. It is found that the CEF energy levels in the
intermediate coupling region can be quantitatively reproduced by our modified
- coupling scheme, when we correctly take into account the corrections in
the order of in addition to the CEF terms and Coulomb interactions
which remain in the limit of =. As an application of the
modified - coupling scheme, we discuss the CEF energy levels of filled
skutterudites with symmetry.Comment: 12 pages, 7 figures. Typeset with jpsj2.cl
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