82,206 research outputs found
Quantum optical diode with semiconductor microcavities
The semiconductor diode, which acts as an electrical rectifier and allows
unidirectional electronic transports, is the key to information processing in
integrated circuits. Analogously, an optical rectifier (or diode) working at
specific target wavelengths has recently becomes a dreaming device in optical
communication and signal processing. In this paper, we propose a scheme to
realize an optical diode for photonic transport at the level of few photons.
The system consists of two spatially overlapping single-mode semiconductor
microcavities coupled via nonlinearities. The photon blockade
is predicted to take place in this system. These photon blockade effects can be
achieved by tuning the frequency of the input laser field (driving field).
Based on those blockades, we derive analytically the single- and two-photon
current in terms of zero and finite-time delayed two-order correlation
function. The results suggest that the system can serve as an single- and
two-photon quantum optical diodes which allow transmission of photons in one
direction much more efficiently than in the other.Comment: 13 pages, 6 figure
Effect of near-earth thunderstorms electric field on the intensity of ground cosmic ray positrons/electrons in Tibet
Monte Carlo simulations are performed to study the correlation between the
ground cosmic ray intensity and near-earth thunderstorms electric field at YBJ
(4300 m a.s.l., Tibet, China). The variations of the secondary cosmic ray
intensity are found to be highly dependent on the strength and polarity of the
electric field. In negative fields and in positive fields greater than 600
V/cm, the total number of ground comic ray positrons and electrons increases
with increasing electric field strength. And these values increase more
obviously when involving a shower with lower primary energy or a higher zenith
angle. While in positive fields ranging from 0 to 600 V/cm, the total number of
ground comic ray positrons and electrons declines and the amplitude is up to
3.1% for vertical showers. A decrease of intensity occurs for inclined showers
in positive fields less than 500 V/cm, which is accompanied by smaller
amplitudes. In this paper, the intensity changes are discussed, especially
concerning the decreases in positive electric fields. Our simulation results
are in good agreement with ground-based experimental results obtained from
ARGO-YBJ and the Carpet air shower array. These results could be helpful in
understanding the acceleration mechanisms of secondary charged particles caused
by an atmospheric electric field.Comment: 17pages,15figure
Quantum response theory for open systems and its application to Hall conductance
Quantum linear response theory considers only the response of a closed
quantum system to a perturbation up to first order in the perturbation. This
theory breaks down when the system subjects to environments and the response up
to second order in perturbation is not negligible. In this paper, we develop a
quantum nonlinear response theory for open systems. We first formulate this
theory in terms of general susceptibility, then apply it to deriving the Hall
conductance for the open system at finite temperature. Taking the two-band
model as an example, we derive the Hall conductance for the two-band model. We
calculate the Hall conductance for a two-dimensional ferromagnetic electron gas
and a two-dimensional lattice model via different expressions for
. The results show that the transition
points of topological phase almost remain unchanged in the presence of
environments.Comment: 10 pages, 6 figure
Wax and wane of the cross-sectional momentum and contrarian effects: Evidence from the Chinese stock markets
This paper investigates the time-varying risk-premium relation of the Chinese
stock markets within the framework of cross-sectional momentum and contrarian
effects by adopting the Capital Asset Pricing Model and the French-Fama three
factor model. The evolving arbitrage opportunities are also studied by
quantifying the performance of time-varying cross-sectional momentum and
contrarian effects in the Chinese stock markets. The relation between the
contrarian profitability and market condition factors that could characterize
the investment context is also investigated. The results reveal that the
risk-premium relation varies over time, and the arbitrage opportunities based
on the contrarian portfolios wax and wane over time. The performance of
contrarian portfolios are highly dependent on several market conditions. The
periods with upward trend of market state, higher market volatility and
liquidity, lower macroeconomics uncertainty are related to higher contrarian
profitability. These findings are consistent with the Adaptive Markets
Hypothesis and have practical implications for market participants
Noise induced entanglement
We discuss the generation of entangled states of two two-level atoms coupled
simultaneously with a dissipated atom. The dissipation of the atom is supposed
to come from its coupling to a noise with adjustable intensity. We describe how
the entanglement between the atoms arise in such a situation, and wether a
noise except the white one could help preparation of entanglement. Besides, we
confirm that the entanglement is maximized for intermediate values of the noise
intensity, while it is a monotonic function of the spontaneous rates. This
resembles the phenomenon of stochastic resonance and sheds more light on the
idea to exploit noise in quantum information processing.Comment: 5 pages, 3 figure
Thermal entanglement of Bosonic atoms in an optical lattice with nonlinear couplings
The thermal entanglement of two spin-1 atoms with nonlinear couplings in
optical lattices is investigated in this paper. It is found that the nonlinear
couplings favor the thermal entanglement creating. The dependence of the
thermal entanglement in this system on the linear coupling, the nonlinear
coupling, the magnetic field and temperature is also presented. The results
show that the nonlinear couplings really change the feature of the thermal
entanglement in the system, increasing the nonlinear coupling constant
increases the critical magnetic field and the threshold temperature.Comment: 5 pagues, 3 figure
Is monogamy of entanglement geometrical?
This work aims to understand the monogamy of quantum entanglement from a
geometrical point of view. By regarding quantum entanglement as a geometrical
structure on the state space of quantum systems and attributing all
entanglement related properties as emergent from this geometry of entanglement,
we assume there exists a genuine general monogamous relation of quantum
entanglement w.r.t. a correspondent genuine entanglement measure Q* which
possesses an underlying geometrical origin. We speculate that the monogamous
relations w.r.t. an entanglement measure Q can be understood by comparing the
different dimension dependencies of the measure Q and Q*. We gave evidences of
our conjecture by readdressing two observed properties of the monogamy
relations from this geometrical standpoint. Besides the phenomenal explanation
of the monogamy of entanglement, we also discussed a fibre bundle structure
based candidate solution for the geometry of entanglement and explained how
this idea is related to the ER=EPR conjecture and other interesting quantum
information processing problems including monogamy of entanglement,
entanglement distillation, bound entanglement and activation, and entanglement
catalyst.Comment: 23 pages, 8 figure
Fastest Frozen Temperature for a Thermodynamic System
For a thermodynamic system obeying both the equipartition theorem in high
temperature and the third law in low temperature, the curve showing
relationship between the specific heat and the temperature has two common
behaviors:\ it terminates at zero when the temperature is zero Kelvin and
converges to a constant as temperature is higher and higher. Since it is always
possible to find the characteristic temperature to mark the excited
temperature as the specific heat almost reaches the equipartition value, it is
reasonable to find a temperature in low temperature interval, complementary to
. The present study reports a possibly universal existence of the such a
temperature , defined by that at which the specific heat falls
\textit{fastest} along with decrease of the temperature. For the Debye model of
solids, above the temperature the Debye's law starts to fail.Comment: 8 pages, 5 figures, manuscript completely rewritten and presentation
greatly improve
Two superconducting phases and their characteristics in layered BaTi2(Sb1-xBix)2O with x=0.16
Two correlated superconducting phases are identified in layered
superconductor BaTi2(Sb1-xBix)2O (x=0.16), with the superconducting transition
temperatures of TC = 6 K (the high TC phase) and 3.4 K (the low TC Phase),
respectively. The 6 K superconducting phase appears firstly in the as-prepared
sample and can decay into the low TC phase by exposing to ambient atmosphere
for certain duration. Especially the high TC phase can reappear from the
decayed sample with the low TC phase by vacuum annealing. It is also found that
the CDW/SDW order occurs only with the 6 K superconducting phase. These notable
features and alteration of superconductivity due to the post-processing and
external pressure can be explained by the scenario of electronic
phase-separation.Comment: 12 pages, 4 figure
Entangling Two-Atom Through Cooperative Interaction Under Stimulated Emission
We discuss the generation of two-atom entanglement inside a resonant
microcavity under stimulated emission (STE) interaction. The amount of
entanglement is shown based on different atomic initial state. For each kind of
intial state, we obtain the entanglement period and the entanglement critical
point, which are found to deeply depend on driving field density. In case of
atomic state , the entanglement can be induced due to STE. In case of
atomic state , there is a competition between driving field indued
entanglement and STE induced entanglement. When two atoms are initially in , we can find a lumbar region where STE increases the amount and period of
entanglement.Comment: 11 pages, 5 figure
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