4,612 research outputs found
Resonance fluorescence beyond the dipole approximation of a quantum dot in a plasmonic nanostructure
The mesoscopic characteristics of a quantum dot (QD), which make the dipole
approximation (DA) break down, provide a new dimension to manipulate
light-matter interaction [M. L. Andersen et al., Nat. Phys. 7, 215 (2011)].
Here we investigate the power spectrum and the second-order correlation
property of the fluorescence from a resonantly driven QD placed on a planar
metal. It is revealed that due to the pronounced QD spatial extension and the
dramatic variation of the triggered surface plasmon near the metal, the
fluorescence has a notable contribution from the quadrupole moment. The
{\pi}-rotation symmetry of the fluorescence to the QD orientation under the DA
is broken. By manipulating the QD orientation and quadrupole moment, the
spectrum can be switched between the Mollow triplet and a single peak, and the
fluorescence characterized by the antibunching in the second-order correlation
function can be changed from the weak to the strong radiation regime. Our
result is instructive for utilizing the unique mesoscopic effects to develop
nanophotonic devices
Cosmic Constraints to wCDM Model from Strong Gravitational Lensing
In this paper, we study the cosmic constraint to CDM model via
strong gravitational lensing systems which are complied from SLACS, BELLS, LSD
and SL2S surveys, where the ratio between two angular diameter distances
is taken as a cosmic observable. To obtain
this ratio, we adopt two strong lensing models: one is the singular isothermal
sphere model (SIS), the other one is the power-law density profile (PLP) model.
Via the Markov Chain Mote Carlo method, the posterior distribution of the
cosmological model parameters space is obtained. The results show that the
cosmological model parameters are not sensitive to the parameterized forms of
the power-law index . Furthermore, the PLP model gives a relative
tighter constraint to the cosmological parameters than that of the SIS model.
The predicted value of by SIS model is
compatible with that obtained by {\it Planck}2015: .
However, the value of based on the PLP model is
smaller and has tension with that obtained by {\it Planck}2015
result. This discrepancy maybe come from the systematic errors.Comment: 6 pages, 2 figure
Symmetry energy of super-dense neutron-rich matter from integrating barotropic pressures in neutron stars and heavy-ion reactions
Within the minimum model of neutron stars (NS) consisting of neutrons,
protons and electrons, a new approach is proposed for inferring the symmetry
energy of super-dense neutron-rich nucleonic matter above twice the saturation
density of nuclear matter directly from integrating iteratively
barotropic pressures in both neutron stars and heavy-ion reactions.
Simultaneously, the proton fraction of NSs at equilibrium is extracted
as a function of baryon density from the same procedure. An application of this
approach using the NS pressure from GW170817 and the pressure in cold symmetric
nuclear matter (SNM) extracted earlier by analyzing nuclear collective flow
data in relativistic heavy-ion collisions provides a useful constraining band
for the symmetry energy above .Comment: More discussions and references added. Phys. Lett. B in pres
Exact decoherence-free state of two distant quantum systems in a non-Markovian environment
Decoherence-free state (DFS) encoding supplies a useful way to avoid the
detrimental influence of the environment on quantum information processing. The
DFS was previously well established in either the two subsystems locating at
the same spatial position or the dynamics under the Born--Markovian
approximation. Here, we investigate the exact DFS of two spatially separated
quantum systems consisting of two-level systems or harmonic oscillators coupled
to a common non-Markovian zero-temperature bosonic environment. The exact
distance-dependent DFS and the explicit criterion for forming the DFS are
obtained analytically, which reveals that the DFS can arise only in
one-dimensional environment. It is remarkable to further find that the DFS is
just the system-reduced state of the famous bound state in the continuum (BIC)
of the total system predicted by Wigner and von Neumann. On the one hand our
result gives insight into the physical nature of the DFS, and on the other hand
it supplies an experimentally accessible scheme to realize the mathematically
curious BIC in the standard quantum optical systems.Comment: 7 pages, 3 figure
Computing optimal interfacial structure of ordered phases
We propose a general framework of computing interfacial structure. If an
ordered phase is involved, the interfacial structure can be obtained by simply
minimizing the free energy with compatible boundary conditions. The framework
is applied to Landau- Brazovskii model and works efficiently
Computing optimal interfacial structure of modulated phases
We propose a general framework of computing interfacial structures between
two modulated phases. Specifically we propose to use a computational box
consisting of two half spaces, each occupied by a modulated phase with given
position and orientation. The boundary conditions and basis functions are
chosen to be commensurate with the bulk structures. It is observed that the
ordered nature of modulated structures stabilizes the interface, which enables
us to obtain optimal interfacial structures by searching local minima of the
free energy landscape. The framework is applied to the Landau-Brazovskii model
to investigate interfaces between modulated phases with different relative
positions and orientations. Several types of novel complex interfacial
structures are obtained from the calculations.Comment: 15 pages, 7 figures. arXiv admin note: substantial text overlap with
arXiv:1511.0362
Generation of N-atom W-class states in spatially separated cavities
We propose a feasible and efficient scheme to generate -atom -class
states in spatially separated cavities without using any classical driving
pulses. We adopt the model in which the couplings between different atoms are
mediated only by virtual excitations of the cavity and fiber fields, so the
scheme is insensitive to the cavity decay and fiber photon leakage. We carry
out both theoretical investigation in a decoherence-free subspace and numerical
calculation accounting for decoherence due to the atomic spontaneous emission
as well as the decay of cavity and fiber modes. The theoretical and numerical
results agree in the large atom-cavity detuning regime. Our scheme proves to be
useful in scalable distributed quantum networks.Comment: 12 pages, 5 figures, Accepted by J. Opt. Soc. Am.
One-step generation of multi-atom Greenberger-Horne-Zeilinger states in separate cavities via adiabatic passage
We propose a scheme to deterministically generate Greenberger-Horne-Zeilinger
states of atoms trapped in spatially separated cavities connected by
optical fibers. The scheme is based on the technique of fractional stimulated
Raman adiabatic passage which is one-step in the sense that one needs just wait
for the desired entangled state to be generated in the stationary regime. The
parametrized shapes of the Rabi frequencies of the classical fields that drive
the two end atoms are chosen appropriately to realize the scheme. We also show
numerically that the proposed scheme is insensitive to the fluctuations of the
pulses' parameters and, at the same time, robust against decoherence caused by
the dissipation due to fiber decay. Moreover, a relatively high fidelity can be
obtained even in the presence of cavity decay and atomic spontaneous emission.Comment: Accepted by JOSA
Generation of stable entanglement between two cavity mirrors by squeezed-reservoir engineering
The generation of quantum entanglement of macroscopic or mesoscopic bodies in
mechanical motion is generally bounded by the thermal fluctuation exerted by
their environments. Here we propose a scheme to establish stationary
entanglement between two mechanically oscillating mirrors of a cavity. It is
revealed that, by applying a broadband squeezed laser acting as a
squeezed-vacuum reservoir to the cavity, a stable entanglement between the
mechanical mirrors can be generated. Using the adiabatic elimination and master
equation methods, we analytically find that the generated entanglement is
essentially determined by the squeezing of the relative momentum of the
mechanical mirrors, which is transferred from the squeezed reservoir through
the cavity. Numerical verification indicates that our scheme is within the
present experimental state of the art of optomechanics.Comment: 9 pages, 6 figure
Shortcuts to adiabatic passage for population transfer and maximum entanglement creation between two atoms in a cavity
We use the approach of "transitionless quantum driving" proposed by Berry to
construct shortcuts to the population transfer and the creation of maximal
entanglement between two -type atoms based on the cavity quantum
electronic dynamics (CQED) system. An effective Hamiltonian is designed by
resorting to an auxiliary excited level, a classical driving field and an extra
cavity field mode to supplement or substitute the original reference
Hamiltonian, and steer the system evolution along its instantaneous eigenstates
in an arbitrarily short time, speeding up the rate of population transfer and
creation of maximal entanglement between the two atoms inside a cavity.
Numerical simulation demonstrates that our shortcuts' performance is robust
against the decoherences caused by atomic spontaneous emission and cavity
photon leakage.Comment: Accepted by Physical Review A as a Regular Articl
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