122 research outputs found
A general study on the volume dependence of spectral weights in lattice field theory
It has been suggested that the volume dependence of the spectral weight could
be utilized to distinguish single and multi-particle states in Monte Carlo
simulations. In a recent study using a solvable model, the Lee model, we found
that this criteria is applicable only for stable particles and narrow
resonances, not for the broad resonances. In this paper, the same question is
addressed within the finite size formalism outlined by L\"uscher. Using a
quantum mechanical scattering model, the conclusion that was found in previous
Lee model study is recovered. Then, following similar arguments as in
L\"uscher's, it is argued that the result is valid for a general massive
quantum field theory under the same conditions as the L\"uscher's formulae.
Using the spectral weight function, a possibility of extracting resonance
parameters is also pointed out.Comment: 18 pages, no figure
More on volume dependence of spectral weight function
Spectral weight functions are easily obtained from two-point correlation
functions and they might be used to distinguish single-particle from
multi-particle states in a finite-volume lattice calculation, a problem crucial
for many lattice QCD simulations. In previous studies, it is shown that the
spectral weight function for a broad resonance shares the typical volume
dependence of a two-particle scattering state i.e. proportional to in a
large cubic box of size while the narrow resonance case requires further
investigation. In this paper, a generalized formula is found for the spectral
weight function which incorporates both narrow and broad resonance cases.
Within L\"uscher's formalism, it is shown that the volume dependence of the
spectral weight function exhibits a single-particle behavior for a extremely
narrow resonance and a two-particle behavior for a broad resonance. The
corresponding formulas for both and channels are derived. The
potential application of these formulas in the extraction of resonance
parameters are also discussed
Radiative transitions in charmonium from twisted mass lattice QCD
We present a study for charmonium radiative transitions:
, and
using twisted mass lattice QCD gauge
configurations. The single-quark vector form factors for and
are also determined. The simulation is performed at a lattice
spacing of fm and the lattice size is . After
extrapolation of lattice data at nonzero to 0, we compare our results
with previous quenched lattice results and the available experimental values.Comment: typeset with revtex, 15 pages, 11 figures, 4 table
Storage of multiple single-photon pulses emitted from a quantum dot in a solid-state quantum memory
Quantum repeaters are critical components for distributing entanglement over
long distances in presence of unavoidable optical losses during transmission.
Stimulated by Duan-Lukin-Cirac-Zoller protocol, many improved quantum-repeater
protocols based on quantum memories have been proposed, which commonly focus on
the entanglement-distribution rate. Among these protocols, the elimination of
multi-photons (multi-photon-pairs) and the use of multimode quantum memory are
demonstrated to have the ability to greatly improve the
entanglement-distribution rate. Here, we demonstrate the storage of
deterministic single photons emitted from a quantum dot in a
polarization-maintaining solid-state quantum memory; in addition,
multi-temporal-mode memory with , and narrow single-photon pulses
is also demonstrated. Multi-photons are eliminated, and only one photon at most
is contained in each pulse. Moreover, the solid-state properties of both
sub-systems make this configuration more stable and easier to be scalable. Our
work will be helpful in the construction of efficient quantum repeaters based
on all-solid-state devicesComment: Published version, including supplementary materia
High-efficiency broadband second harmonic generation in single hexagonal GaAs nanowire
AbstractIn this paper, we investigate second harmonic generation in a single hexagonal GaAs nanowire. An excellent frequency converter based on this nanowire excited using a femtosecond laser is demonstrated to operate over a range from 730 nm to 1960 nm, which is wider than previously reported ranges for nanowires in the literature. The converter always operates with a high conversion efficiency of ~10−5 W−1 which is ~103 times higher than that obtained from the surface of bulk GaAs. This nanoscale nolinear optical converter that simultaneously owns high efficiency and broad bandwidth may open a new way for application in imaging, bio-sensing and on-chip all-optical signal processing operations.</jats:p
High-performance infrared photodetectors based on InAs/InAsSb/AlAsSb superlattice for 3.5 µm cutoff wavelength spectra
High-performance infrared p-i-n photodetectors based on InAs/InAsSb/AlAsSb superlattices on GaSb substrate have been demonstrated at 300K. These photodetectors exhibit 50% and 100% cut-off wavelength of ∼3.2 µm and ∼3.5 µm, respectively. Under -130 mV bias voltage, the device exhibits a peak responsivity of 0.56 A/W, corresponding to a quantum efficiency (QE) of 28%. The dark current density at 0 mV and -130 mV bias voltage are 8.17 × 10−2 A/cm2 and 5.02 × 10−1 A/cm2, respectively. The device exhibits a saturated dark current shot noise limited specific detectivity (D*) of 3.43 × 109 cm·Hz1/2/W (at a peak responsivity of 2.5 µm) under -130 mV of applied bias
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