7,163 research outputs found
On Quantum Jumps, Events and Spontaneous Localization Models
We propose a definite meaning to the concepts of "experiment", "measurement"
and "event" in the event-enhanced formalism of quantum theory. A minimal
piecewise deterministic process is given that can be used for a computer
simulation of real time series of experiments on single quantum objects. As an
example a generalized cloud chamber is described, including multiparticle case.
Relation to the GRW spontaneous localization model is discussed. The second
revised version of the paper contains references to papers by other authors
that are are aiming in the same direction: to enhance quantum theory in such a
way that it will provide stochastic description of events triggered by
individual quantum systems.Comment: 20 page
A Way Out of the Quantum Trap
We review Event Enhanced Quantum Theory (EEQT). In Section 1 we address the
question "Is Quantum Theory the Last Word". In particular we respond to some of
recent challenging staments of H.P. Stapp. We also discuss a possible future of
the quantum paradigm - see also Section 5. In Section 2 we give a short sketch
of EEQT. Examples are given in Section 3. Section 3.3 discusses a completely
new phenomenon - chaos and fractal-like phenomena caused by a simultaneous
"measurement" of several non-commuting observables (we include picture of
Barnsley's IFS on unit sphere of a Hilbert space). In Section 4 we answer
"Frequently Asked Questions" concerning EEQT.Comment: Replacement. Corrected affiliation. Latex, one .jpg figure. To appear
in Proc. Conf. Relativistic Quantum Measurements, Napoli 1998, Ed. F.
Petruccion
Investigation of remote sensing techniques of measuring soil moisture
Major activities described include development and evaluation of theoretical models that describe both active and passive microwave sensing of soil moisture, the evaluation of these models for their applicability, the execution of a controlled field experiment during which passive microwave measurements were acquired to validate these models, and evaluation of previously acquired aircraft microwave measurements. The development of a root zone soil water and soil temperature profile model and the calibration and evaluation of gamma ray attenuation probes for measuring soil moisture profiles are considered. The analysis of spatial variability of soil information as related to remote sensing is discussed as well as the implementation of an instrumented field site for acquisition of soil moisture and meteorologic information for use in validating the soil water profile and soil temperature profile models
Measurement of Untruncated Nuclear Spin Interactions via Zero- to Ultra-Low-Field Nuclear Magnetic Resonance
Zero- to ultra-low-field nuclear magnetic resonance (ZULF NMR) provides a new
regime for the measurement of nuclear spin-spin interactions free from effects
of large magnetic fields, such as truncation of terms that do not commute with
the Zeeman Hamiltonian. One such interaction, the magnetic dipole-dipole
coupling, is a valuable source of spatial information in NMR, though many terms
are unobservable in high-field NMR, and the coupling averages to zero under
isotropic molecular tumbling. Under partial alignment, this information is
retained in the form of so-called residual dipolar couplings. We report zero-
to ultra-low-field NMR measurements of residual dipolar couplings in
acetonitrile-2-C aligned in stretched polyvinyl acetate gels. This
represents the first investigation of dipolar couplings as a perturbation on
the indirect spin-spin -coupling in the absence of an applied magnetic
field. As a consequence of working at zero magnetic field, we observe terms of
the dipole-dipole coupling Hamiltonian that are invisible in conventional
high-field NMR. This technique expands the capabilities of zero- to
ultra-low-field NMR and has potential applications in precision measurement of
subtle physical interactions, chemical analysis, and characterization of local
mesoscale structure in materials.Comment: 6 pages, 3 figure
Non-Markovian dynamics for bipartite systems
We analyze the appearance of non-Markovian effects in the dynamics of a
bipartite system coupled to a reservoir, which can be described within a class
of non-Markovian equations given by a generalized Lindblad structure. A novel
master equation, which we term quantum Bloch-Boltzmann equation, is derived,
describing both motional and internal states of a test particle in a quantum
framework. When due to the preparation of the system or to decoherence effects
one of the two degrees of freedom is amenable to a classical treatment and not
resolved in the final measurement, though relevant for the interaction with the
reservoir, non-Markovian behaviors such as stretched exponential or power law
decay of coherences can be put into evidence.Comment: published version, 15 pages, revtex, no figure
Cosmological Baryon Sound Waves Coupled with the Primeval Radiation
The fluid equations for the baryon-electron system in an expanding universe
are derived from the Boltzmann equation. The effect of the Compton interaction
is taken into account properly in order to evaluate the photon-electron
collisional term. As an application, the acoustic motions of the
baryon-electron system after recombination are investigated. The effective
adiabatic index is computed for sound waves of various wavelengths,
assuming the perturbation amplitude is small. The oscillations are found to be
dumped when changes from between 1 (for an isothermal process) to 5/3
(for an adiabatic process).Comment: 20 pages, Revtex, Accepted for publication in Phys. Rev.
Density-potential mappings in quantum dynamics
In a recent letter [Europhys. Lett. 95, 13001 (2011)] the question of whether
the density of a time-dependent quantum system determines its external
potential was reformulated as a fixed point problem. This idea was used to
generalize the existence and uniqueness theorems underlying time-dependent
density functional theory. In this work we extend this proof to allow for more
general norms and provide a numerical implementation of the fixed-point
iteration scheme. We focus on the one-dimensional case as it allows for a more
in-depth analysis using singular Sturm-Liouville theory and at the same time
provides an easy visualization of the numerical applications in space and time.
We give an explicit relation between the boundary conditions on the density and
the convergence properties of the fixed-point procedure via the spectral
properties of the associated Sturm-Liouville operator. We show precisely under
which conditions discrete and continuous spectra arise and give explicit
examples. These conditions are then used to show that in the most physically
relevant cases the fixed point procedure converges. This is further
demonstrated with an example.Comment: 20 pages, 8 figures, 3 table
Raman and nuclear magnetic resonance investigation of alkali metal vapor interaction with alkene-based anti-relaxation coating
The use of anti-relaxation coatings in alkali vapor cells yields substantial
performance improvements by reducing the probability of spin relaxation in wall
collisions by several orders of magnitude. Some of the most effective
anti-relaxation coating materials are alpha-olefins, which (as in the case of
more traditional paraffin coatings) must undergo a curing period after cell
manufacturing in order to achieve the desired behavior. Until now, however, it
has been unclear what physicochemical processes occur during cell curing, and
how they may affect relevant cell properties. We present the results of
nondestructive Raman-spectroscopy and magnetic-resonance investigations of the
influence of alkali metal vapor (Cs or K) on an alpha-olefin, 1-nonadecene
coating the inner surface of a glass cell. It was found that during the curing
process, the alkali metal catalyzes migration of the carbon-carbon double bond,
yielding a mixture of cis- and trans-2-nonadecene.Comment: 5 pages, 6 figure
Classical interventions in quantum systems. I. The measuring process
The measuring process is an external intervention in the dynamics of a
quantum system. It involves a unitary interaction of that system with a
measuring apparatus, a further interaction of both with an unknown environment
causing decoherence, and then the deletion of a subsystem. This description of
the measuring process is a substantial generalization of current models in
quantum measurement theory. In particular, no ancilla is needed. The final
result is represented by a completely positive map of the quantum state
(possibly with a change of the dimensions of ). A continuous limit of the
above process leads to Lindblad's equation for the quantum dynamical semigroup.Comment: Final version, 14 pages LaTe
- …