6,532 research outputs found
Measurement of energy eigenstates by a slow detector
We propose a method for a weak continuous measurement of the energy
eigenstates of a fast quantum system by means of a "slow" detector. Such a
detector is only sensitive to slowly-changing variables, e. g. energy, while
its back-action can be limited solely to decoherence of the eigenstate
superpositions. We apply this scheme to the problem of detection of quantum
jumps between energy eigenstates in a harmonic oscillator.Comment: 4 page
Local flow management/profile descent algorithm. Fuel-efficient, time-controlled profiles for the NASA TSRV airplane
The Local Flow Management/Profile Descent (LFM/PD) algorithm designed for the NASA Transport System Research Vehicle program is described. The algorithm provides fuel-efficient altitude and airspeed profiles consistent with ATC restrictions in a time-based metering environment over a fixed ground track. The model design constraints include accommodation of both published profile descent procedures and unpublished profile descents, incorporation of fuel efficiency as a flight profile criterion, operation within the performance capabilities of the Boeing 737-100 airplane with JT8D-7 engines, and conformity to standard air traffic navigation and control procedures. Holding and path stretching capabilities are included for long delay situations
An investigation of TNAV equipped aircraft in a simulated en route metering environment
This document presents the results of an effort to estimate how often a TNAV (Time Navigation) equipped aircraft could be given a TNAV clearance in the En Route Metering (ERM) system as a function of the percentage of arriving traffic which is TNAV equipped. A fast-time simulation of Denver Stapleton international arrival traffic in the Denver Air Route Traffic Control Center route structure, including en route metering operations, was used to develop data on estimated conflicts, clearance communications and fuel usage for traffic mixes of 25, 50, 75 and 100% TNAV equipped. This study supports an overall effort by NASA to assess the benefits and required technology for using TNAV-equipped aircraft in the ERM environment
Ion trap transducers for quantum electromechanical oscillators
An enduring challenge for contemporary physics is to experimentally observe
and control quantum behavior in macroscopic systems. We show that a single
trapped atomic ion could be used to probe the quantum nature of a mesoscopic
mechanical oscillator precooled to 4K, and furthermore, to cool the oscillator
with high efficiency to its quantum ground state. The proposed experiment could
be performed using currently available technology.Comment: 4 pages, 2 figure
Inverse Spin Hall Effect and Anomalous Hall Effect in a Two-Dimensional Electron Gas
We study the coupled dynamics of spin and charge currents in a
two-dimensional electron gas in the transport diffusive regime. For systems
with inversion symmetry there are established relations between the spin Hall
effect, the anomalous Hall effect and the inverse spin Hall effect. However, in
two-dimensional electron gases of semiconductors like GaAs, inversion symmetry
is broken so that the standard arguments do not apply. We demonstrate that in
the presence of a Rashba type of spin-orbit coupling (broken structural
inversion symmetry) the anomalous Hall effect, the spin Hall and inverse spin
Hall effect are substantially different effects. Furthermore we discuss the
inverse spin Hall effect for a two-dimensional electron gas with Rashba and
Dresselhaus spin-orbit coupling; our results agree with a recent experiment.Comment: 5 page
The Effect of Surface Roughness on the Universal Thermal Conductance
We explain the reduction of the thermal conductance below the predicted
universal value observed by Schwab et al. in terms of the scattering of thermal
phonons off surface roughness using a scalar model for the elastic waves. Our
analysis shows that the thermal conductance depends on two roughness
parameters: the roughness amplitude and the correlation length .
At sufficiently low temperatures the conductance decrease from the universal
value quadratically with temperature at a rate proportional to .
Values of equal to 0.22 and equal to about 0.75 of the width of
the conduction pathway give a good fit to the data.Comment: 10 pages, 5 figures. Ref. added, typo correcte
Analytic regularity for a singularly perturbed system of reaction-diffusion equations with multiple scales: proofs
We consider a coupled system of two singularly perturbed reaction-diffusion
equations, with two small parameters , each
multiplying the highest derivative in the equations. The presence of these
parameters causes the solution(s) to have \emph{boundary layers} which overlap
and interact, based on the relative size of and . We
construct full asymptotic expansions together with error bounds that cover the
complete range . For the present case of analytic
input data, we derive derivative growth estimates for the terms of the
asymptotic expansion that are explicit in the perturbation parameters and the
expansion order
Momentum-resolved evolution of the Kondo lattice into 'hidden-order' in URu2Si2
We study, using high-resolution angle-resolved photoemission spectroscopy,
the evolution of the electronic structure in URu2Si2 at the Gamma, Z and X
high-symmetry points from the high-temperature Kondo-screened regime to the
low-temperature `hidden-order' (HO) state. At all temperatures and symmetry
points, we find structures resulting from the interaction between heavy and
light bands, related to the Kondo lattice formation. At the X point, we
directly measure a hybridization gap of 11 meV already open at temperatures
above the ordered phase. Strikingly, we find that while the HO induces
pronounced changes at Gamma and Z, the hybridization gap at X does not change,
indicating that the hidden-order parameter is anisotropic. Furthermore, at the
Gamma and Z points, we observe the opening of a gap in momentum in the HO
state, and show that the associated electronic structure results from the
hybridization of a light electron band with the Kondo-lattice bands
characterizing the paramagnetic state.Comment: Updated published version. Mansucript + Supplemental Material (8
pages, 9 figures). Submitted 16 September 201
Small quantum networks operating as quantum thermodynamic machines
We show that a 3-qubit system as studied for quantum information purposes can
alternatively be used as a thermodynamic machine when driven in finite time and
interfaced between two split baths. The spins are arranged in a chain where the
working spin in the middle exercises Carnot cycles the area of which defines
the exchanged work. The cycle orientation (sign of the exchanged work) flips as
the difference of bath temperatures goes through a critical value.Comment: RevTeX, 4 pages, 7 figures. Replaced by version accepted for
publication in EP
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