8,407 research outputs found
Cavity quantum electro-optics. II. Input-output relations between traveling optical and microwave fields
In the previous paper [M. Tsang, Phys. Rev. A 81, 063837 (2010), e-print
arXiv:1003.0116], I proposed a quantum model of a cavity electro-optic
modulator, which can coherently couple an optical cavity mode to a microwave
resonator mode and enable novel quantum operations on the two modes, including
laser cooling of the microwave mode, electro-optic entanglement, and
backaction-evading optical measurement of a microwave quadrature. In this
sequel, I focus on the quantum input-output relations between traveling optical
and microwave fields coupled to a cavity electro-optic modulator. With
red-sideband optical pumping, the relations are shown to resemble those of a
beam splitter for the traveling fields, so that in the ideal case of zero
parasitic loss and critical coupling, microwave photons can be coherently
up-converted to "flying" optical photons with unit efficiency, and vice versa.
With blue-sideband pumping, the modulator acts as a nondegenerate parametric
amplifier, which can generate two-mode squeezing and hybrid entangled photon
pairs at optical and microwave frequencies. These fundamental operations
provide a potential bridge between circuit quantum electrodynamics and quantum
optics.Comment: 12 pages, 10 figures, v2: updated and submitte
Multifractality and scale invariance in human heartbeat dynamics
Human heart rate is known to display complex fluctuations. Evidence of
multifractality in heart rate fluctuations in healthy state has been reported
[Ivanov et al., Nature {\bf 399}, 461 (1999)]. This multifractal character
could be manifested as a dependence on scale or beat number of the probability
density functions (PDFs) of the heart rate increments. On the other hand, scale
invariance has been recently reported in a detrended analysis of healthy heart
rate increments [Kiyono et al., Phys. Rev. Lett. {\bf 93}, 178103 (2004)]. In
this paper, we resolve this paradox by clarifying that the scale invariance
reported is actually exhibited by the PDFs of the sum of detrended healthy
heartbeat intervals taken over different number of beats, and demonstrating
that the PDFs of detrended healthy heart rate increments are scale dependent.
Our work also establishes that this scale invariance is a general feature of
human heartbeat dynamics, which is shared by heart rate fluctuations in both
healthy and pathological states
Resonant Shattering of Neutron Star Crusts
The resonant excitation of neutron star (NS) modes by tides is investigated
as a source of short gamma-ray burst (sGRB) precursors. We find that the
driving of a crust-core interface mode can lead to shattering of the NS crust,
liberating ~10^46-10^47 erg of energy seconds before the merger of a NS-NS or
NS-black hole binary. Such properties are consistent with Swift/BAT detections
of sGRB precursors, and we use the timing of the observed precursors to place
weak constraints on the crust equation of state. We describe how a larger
sample of precursor detections could be used alongside coincident gravitational
wave detections of the inspiral by Advanced LIGO class detectors to probe the
NS structure. These two types of observations nicely complement one another,
since the former constrains the equation of state and structure near the
crust-core boundary, while the latter is more sensitive to the core equation of
state.Comment: 5 pages, 2 figures. Accepted to PR
Ziv-Zakai Error Bounds for Quantum Parameter Estimation
I propose quantum versions of the Ziv-Zakai bounds as alternatives to the
widely used quantum Cram\'er-Rao bounds for quantum parameter estimation. From
a simple form of the proposed bounds, I derive both a "Heisenberg" error limit
that scales with the average energy and a limit similar to the quantum
Cram\'er-Rao bound that scales with the energy variance. These results are
further illustrated by applying the bound to a few examples of optical phase
estimation, which show that a quantum Ziv-Zakai bound can be much higher and
thus tighter than a quantum Cram\'er-Rao bound for states with highly
non-Gaussian photon-number statistics in certain regimes and also stay close to
the latter where the latter is expected to be tight.Comment: v1: preliminary result, 3 pages; v2: major update, 4 pages +
supplementary calculations, v3: another major update, added proof of
"Heisenberg" limit, v4: accepted by PR
On the Relationship between Resolution Enhancement and Multiphoton Absorption Rate in Quantum Lithography
The proposal of quantum lithography [Boto et al., Phys. Rev. Lett. 85, 2733
(2000)] is studied via a rigorous formalism. It is shown that, contrary to Boto
et al.'s heuristic claim, the multiphoton absorption rate of a ``NOON'' quantum
state is actually lower than that of a classical state with otherwise identical
parameters. The proof-of-concept experiment of quantum lithography [D'Angelo et
al., Phys. Rev. Lett. 87, 013602 (2001)] is also analyzed in terms of the
proposed formalism, and the experiment is shown to have a reduced multiphoton
absorption rate in order to emulate quantum lithography accurately. Finally,
quantum lithography by the use of a jointly Gaussian quantum state of light is
investigated, in order to illustrate the trade-off between resolution
enhancement and multiphoton absorption rate.Comment: 14 pages, 7 figures, submitted, v2: rewritten in response to
referees' comments, v3: rewritten and extended, v4: accepted by Physical
Review
Proximity Effects in Radiative Transfer
Though the dependence of near-field radiative transfer on the gap between two
planar objects is well understood, that between curved objects is still
unclear. We show, based on the analysis of the surface polariton mediated
radiative transfer between two spheres of equal radii and minimum gap ,
that the near--field radiative transfer scales as as
and as for larger values of up to the far--field limit. We
propose a modified form of the proximity approximation to predict near--field
radiative transfer between curved objects from simulations of radiative
transfer between planar surfaces.Comment: 5 journal pages, 4 figure
Quantum temporal correlations and entanglement via adiabatic control of vector solitons
It is shown that optical pulses with a mean position accuracy beyond the
standard quantum limit can be produced by adiabatically expanding an optical
vector soliton followed by classical dispersion management. The proposed scheme
is also capable of entangling positions of optical pulses and can potentially
be used for general continuous-variable quantum information processing.Comment: 5 pages, 1 figure, v2: accepted by Physical Review Letters, v3: minor
editing and shortening, v4: included the submitted erratu
Effective Dielectric Tensor for Electromagnetic Wave Propagation in Random Media
We derive exact strong-contrast expansions for the effective dielectric
tensor \epeff of electromagnetic waves propagating in a two-phase composite
random medium with isotropic components explicitly in terms of certain
integrals over the -point correlation functions of the medium. Our focus is
the long-wavelength regime, i.e., when the wavelength is much larger than the
scale of inhomogeneities in the medium. Lower-order truncations of these
expansions lead to approximations for the effective dielectric constant that
depend upon whether the medium is below or above the percolation threshold. In
particular, we apply two- and three-point approximations for \epeff to a
variety of different three-dimensional model microstructures, including
dispersions of hard spheres, hard oriented spheroids and fully penetrable
spheres as well as Debye random media, the random checkerboard, and
power-law-correlated materials. We demonstrate the importance of employing
-point correlation functions of order higher than two for high
dielectric-phase-contrast ratio. We show that disorder in the microstructure
results in an imaginary component of the effective dielectric tensor that is
directly related to the {\it coarseness} of the composite, i.e., local
volume-fraction fluctuations for infinitely large windows. The source of this
imaginary component is the attenuation of the coherent homogenized wave due to
scattering. We also remark on whether there is such attenuation in the case of
a two-phase medium with a quasiperiodic structure.Comment: 40 pages, 13 figure
The Discovery of an X-ray/UV Stellar Flare from the Late-K/Early-M Dwarf LMC 335
We report the discovery of an X-ray/UV stellar flare from the source LMC 335,
captured by XMM-Newton in the field of the Large Magellanic Cloud. The flare
event was recorded continuously in X-ray for its first 10 hours from the
precursor to the late decay phases. The observed fluxes increased by more than
two orders of magnitude at its peak in X-ray and at least one in the UV as
compared to quiescence. The peak 0.1-7.0 keV X-ray flux is derived from the
two-temperature APEC model to be ~(8.4 +/- 0.6) x 10^-12 erg cm-2 s-1.
Combining astrometric information from multiple X-ray observations in the
quiescent and flare states, we identify the NIR counterpart of LMC 335 as the
2MASS source J05414534-6921512. The NIR color relations and spectroscopic
parallax characterize the source as a Galactic K7-M4 dwarf at a foreground
distance of (100 - 264) pc, implying a total energy output of the entire event
of ~(0.4 - 2.9) x 10^35 erg. This report comprises detailed analyses of this
late-K / early-M dwarf flare event that has the longest time coverage yet
reported in the literature. The flare decay can be modeled with two exponential
components with timescales of ~28 min and ~4 hours, with a single component
decay firmly ruled out. The X-ray spectra during flare can be described by two
components, a dominant high temperature component of ~40-60MK and a low
temperature component of ~10MK, with a flare loop length of about 1.1-1.3
stellar radius.Comment: 35 pages, 6 figures, 5 tables, accepted for publication in Ap
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