4,033 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
Quantum Energy Teleportation in Spin Chain Systems
We propose a protocol for quantum energy teleportation which transports
energy in spin chains to distant sites only by local operations and classical
communication. By utilizing ground-state entanglement and notion of negative
energy density region, energy is teleported without breaking any physical laws
including causality and local energy conservation. Because not excited physical
entity but classical information is transported in the protocol, the
dissipation rate of energy in transport is expected to be strongly suppressed.Comment: 22 pages, 4 figure, to be published in JPS
End Point of Hawking Evaporation -- Case of Integrable Model
Quantum back reaction due to massless fields may be worked out to a
considerable detail in a variant of integrable dilaton gravity model in two
dimensions. It is shown that there exists a critical mass of collapsing object
of order (cosmological constant), above which the end
point of Hawking evaporation is two disconnected remnants of infinite extent,
each separated by a mouth from the outside region. Deep inside the mouth there
is a universal flux of radiation in all directions, in a form different from
Hawking radiation. Below the critical mass no remnant is left behind, implying
complete Hawking evaporation or even showing no sign of Hawking radiation.
Existence of infinitely many static states of quantum nature is also
demonstrated in this model.Comment: 11pages, TU/93/44
Wormhole and Hawking Radiation
It is shown in a variant of two dimensional dilaton gravity theories that an
arbitrary, localized massive source put in an initially regular spacetime gives
rise to formation of the wormhole classically, without accompanying the
curvature singularity. The semiclassical quantum correction under this wormhole
spacetime yields Hawking radiation. It is expected, with the quantum back
reaction added to the classical equation, that the information loss paradox may
be resolved in this model.Comment: 9 pages, TU-93-44
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
Moving Mirror Model of Hawking Evaporation
The moving mirror model is designed to extract essential features of the
black hole formation and the subsequent Hawking radiation by neglecting
complication due to a finite curvature. We extend this approach to dynamically
treat back reaction against the mirror motion due to Hawking radiation. It is
found that a unique model in two spacetime dimensions exists in which Hawking
radiation completely stops and the end point of evaporation contains a
disconnected remnant. When viewed from asymptotic observers at one side of the
spacetime, quantum mechanical correlation is recovered in the end. Although the
thermal stage accompanying short range correlation may last for an arbitrarily
long period, at a much longer time scale a long tail of non-thermal correlation
is clearly detected.Comment: 39 pages, TU-94-452 (Corrupted figure file has been replaced. No
change of the text.
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.
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