21,587 research outputs found
GHZ-type and W-type entangled coherent states: generation and Bell-type inequality tests without photon counting
We study GHZ-type and W-type three-mode entangled coherent states. Both the
types of entangled coherent states violate Mermin's version of the Bell
inequality with threshold photon detection (i.e., without photon counting).
Such an experiment can be performed using linear optics elements and threshold
detectors with significant Bell violations for GHZ-type entangled coherent
states. However, to demonstrate Bell-type inequality violations for W-type
entangled coherent states, additional nonlinear interactions are needed. We
also propose an optical scheme to generate W-type entangled coherent states in
free-traveling optical fields. The required resources for the generation are a
single-photon source, a coherent state source, beam splitters, phase shifters,
photodetectors, and Kerr nonlinearities. Our scheme does not necessarily
require strong Kerr nonlinear interactions, i.e., weak nonlinearities can be
used for the generation of the W-type entangled coherent states. Furthermore,
it is also robust against inefficiencies of the single-photon source and the
photon detectors.Comment: 8 pages, 5 figures, to be published in Phys. Rev.
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How Does Wind Project Performance Change with Age in the United States?
Wind-plant performance declines with age, and the rate of decline varies between regions. The rate of performance decline is important when determining wind-plant financial viability and expected lifetime generation. We determine the rate of age-related performance decline in the United States wind fleet by evaluating generation records from 917 plants. We find the rate of performance decline to be 0.53%/year for older vintages of plants and 0.17%/year for newer vintages of plants on an energy basis for the first 10 years of operation, which is on the lower end of prior estimates in Europe. Unique to the United States, we find a significant drop in performance by 3.6% after 10 years, as plants lose eligibility for the production tax credit. Certain plant characteristics, such as the ratio of blade length to nameplate capacity, influence the rate of performance decline. These results indicate that the performance decline rate can be partially managed and influenced by policy
Transfer of Nonclassical Properties from A Microscopic Superposition to Macroscopic Thermal States in The High Temperature Limit
We present several examples where prominent quantum properties are
transferred from a microscopic superposition to thermal states at high
temperatures. Our work is motivated by an analogy of Schrodinger's cat paradox,
where the state corresponding to the virtual cat is a mixed thermal state with
a large average photon number. Remarkably, quantum entanglement can be produced
between thermal states with nearly the maximum Bell-inequality violation even
when the temperatures of both modes approach infinity.Comment: minor corrections, acknowledgments added, Phys.Rev.Lett., in pres
Ground-Motion Observations at Hotel Montana during the M 7.0 2010 Haiti Earthquake: Topography or Soil Amplification?
Unusually severe structural damage was reported during the 2010 M 7.0 Haiti earthquake in the vicinity of Hotel Montana, located on top of a ridge in the district of PĂ©tionville. Prompted by the observations, U.S. Geological Survey seismic stations were deployed, and aftershock recordings indicated groundâmotion amplification on the top of the hill compared to adjacent stations on reference site conditions. The presence of topographic relief has been shown to significantly aggravate the consequences of strong ground motion during past events, and topographic effects were brought forward to explain the observations. In this paper, we test the hypothesis of topographic amplification as the dominant factor that contributed to the damage concentration in the vicinity of Hotel Montana. We initially conduct numerical simulations of the ridge seismic response assuming elastic homogeneous site conditions, and show that numerical predictions of topographic amplification disagree with the field data both in amplitude and in frequency. Conversely, while 1D groundâresponse analyses for the site conditions at the hilltop predict amplification in the same frequency range as the field data, they significantly underestimate the recorded amplitude. We then conduct numerical simulations of the foothill ridge response to seismic motion while accounting for soil layering, and qualitatively demonstrate that the recorded amplification is most likely attributed to coupled siteâtopographic amplification effects, namely to seismic waves trapped in the soft soil layers of the near surface, amplified as a consequence of reverberations, and further modified due to diffraction and scattering upon incidence on the irregular ground surface. Parametric investigations of the topographyâsoil amplification coupling effects are then conducted, and our results show that when accounting for a hypothetical soilâbedrock interface at 100 m depth, predictions are in excellent agreement with the observed motion
Quantum Nonlocality for a Mixed Entangled Coherent State
Quantum nonlocality is tested for an entangled coherent state, interacting
with a dissipative environment. A pure entangled coherent state violates Bell's
inequality regardless of its coherent amplitude. The higher the initial
nonlocality, the more rapidly quantum nonlocality is lost. The entangled
coherent state can also be investigated in the framework of Hilbert
space. The quantum nonlocality persists longer in Hilbert space.
When it decoheres it is found that the entangled coherent state fails the
nonlocality test, which contrasts with the fact that the decohered entangled
state is always entangled.Comment: 20 pages, 7 figures. To be published in J. Mod. Op
Entanglement of mixed macroscopic superpositions: an entangling-power study
We investigate entanglement properties of a recently introduced class of
macroscopic quantum superpositions in two-mode mixed states. One of the tools
we use in order to infer the entanglement in this non-Gaussian class of states
is the power to entangle a qubit system. Our study reveals features which are
hidden in a standard approach to entanglement investigation based on the
uncertainty principle of the quadrature variables. We briefly describe the
experimental setup corresponding to our theoretical scenario and a suitable
modification of the protocol which makes our proposal realizable within the
current experimental capabilities.Comment: 9 pages, 7 figures, RevTeX
Purification and detection of entangled coherent states
In [J. C. Howell and J. A. Yeazell, Phys. Rev. A 62, 012102 (2000)], a
proposal is made to generate entangled macroscopically distinguishable states
of two spatially separated traveling optical modes. We model the decoherence
due to light scattering during the propagation along an optical transmission
line and propose a setup allowing an entanglement purification from a number of
preparations which are partially decohered due to transmission. A purification
is achieved even without any manual intervention. We consider a nondemolition
configuration to measure the purity of the state as contrast of interference
fringes in a double-slit setup. Regarding the entangled coherent states as a
state of a bipartite quantum system, a close relationship between purity and
entanglement of formation can be obtained. In this way, the contrast of
interference fringes provides a direct means to measure entanglement.Comment: 9 pages, 6 figures, using Revtex
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