13,054 research outputs found
Energy-Entanglement Relation for Quantum Energy Teleportation
Protocols of quantum energy teleportation (QET), while retaining causality
and local energy conservation, enable the transportation of energy from a
subsystem of a many-body quantum system to a distant subsystem by local
operations and classical communication through ground-state entanglement. We
prove two energy-entanglement inequalities for a minimal QET model. These
relations help us to gain a profound understanding of entanglement itself as a
physical resource by relating entanglement to energy as an evident physical
resource.Comment: 16 pages, 1 figure, to appear in Physics Letter
Key Role of Orbital Anisotropy in Geometrically Frustrated Electron System
By using the density matrix renormalization group method, we investigate
ground- and excited-state properties of the e_g-orbital degenerate Hubbard
model at quarter filling for two kinds of lattices, zigzag chain and ladder. In
the zigzag chain, the system is effectively regarded as a decoupled double
chain of the S=1/2 antiferromagnetic Heisenberg model, and the spin gap is
approximately zero, similar to the case of weakly coupled Heisenberg chains. On
the other hand, in the ladder, the spin correlation on the rung remains robust
and the spin gap exists.Comment: 2 pages, 2 figures, Proceedings of SCES'04 (July 26-30, 2004,
Karlsruhe
Multipole Fluctuations in Filled Skutterudites
In order to clarify exotic multipole properties of filled skutterudites, we
evaluate multipole susceptibility for =15, where is the local
-electron number, on the basis of a multiorbital Anderson model constructed
using the - coupling scheme. For =1, magnetic fluctuations dominate
over low-temperature electronic properties, while for =2 and 4, electronic
states are dominated by both magnetic and quadrupole fluctuations. For =3
and 5, octupole fluctuations are found to be significant, depending on the
crystalline electric field potential. We discuss possible relevance of the
results to actual materials.Comment: 4 pages, 3 figures, JPSJ2.cls. To be published in J. Phys. Soc. Jp
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
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
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