314 research outputs found
The gravity-related decoherence master equation from hybrid dynamics
Canonical coupling between classical and quantum systems cannot result in
reversible equations, rather it leads to irreversible master equations.
Coupling of quantized non-relativistic matter to gravity is illustrated by a
simplistic example. The heuristic derivation yields the theory of
gravity-related decoherence proposed longtime ago by Penrose and the author.Comment: 9pp, extended version of invited talk at Fifth International Workshop
DICE2010 (Castello Pasquini/Castiglioncello/Tuscany, Sept. 13-17, 2010
Quantum linear Boltzmann equation with finite intercollision time
Inconsistencies are pointed out in the usual quantum versions of the
classical linear Boltzmann equation constructed for a quantized test particle
in a gas. These are related to the incorrect formal treatment of momentum
decoherence. We prove that ideal collisions would result in complete momentum
decoherence, the persistence of coherence is only due to the finite
intercollision time. A corresponding novel quantum linear Boltzmann equation is
proposed.Comment: 5p
Calculation of X-Ray Signals from Karolyhazy Hazy Space-Time
Karolyhazy's hazy space-time model, invented for breaking down macroscopic
interferences, employs wave-like gravity disturbances. If so, then electric
charges would radiate permanently. Here we discuss the observational
consequences of the radiation. We find that such radiation is excluded by
common experimental situations.Comment: 7 pages, PlainTe
Notes on Certain Newton Gravity Mechanisms of Wave Function Localisation and Decoherence
Both the additional non-linear term in the Schr\"odinger equation and the
additional non-Hamiltonian term in the von Neumann equation, proposed to ensure
localisation and decoherence of macro-objects, resp., contain the same
Newtonian interaction potential formally. We discuss certain aspects that are
common for both equations. In particular, we calculate the enhancement of the
proposed localisation and/or decoherence effects, which would take place if one
could lower the conventional length-cutoff and resolve the mass density on the
interatomic scale.Comment: 8pp LaTex, Submitted to J. Phys. A: Math-Gen, for the special issue
``The Quantum Universe'' in honor of G. C. Ghirard
Coupled Ito equations of continuous quantum state measurement, and estimation
We discuss a non-linear stochastic master equation that governs the
time-evolution of the estimated quantum state. Its differential evolution
corresponds to the infinitesimal updates that depend on the time-continuous
measurement of the true quantum state. The new stochastic master equation
couples to the two standard stochastic differential equations of
time-continuous quantum measurement. For the first time, we can prove that the
calculated estimate almost always converges to the true state, also at
low-efficiency measurements. We show that our single-state theory can be
adapted to weak continuous ensemble measurements as well.Comment: 5 pages, RevTeX4. In version v2 some minor revisions and
clarifications have been incorporated. Moreover, a new reference has been
included. Accepted for publication in Journal of Physics A: Mathematical and
Genera
Robustness and diffusion of pointer states
Classical properties of an open quantum system emerge through its interaction
with other degrees of freedom (decoherence). We treat the case where this
interaction produces a Markovian master equation for the system. We derive the
corresponding distinguished local basis (pointer basis) by three methods. The
first demands that the pointer states mimic as close as possible the local
non-unitary evolution. The second demands that the local entropy production be
minimal. The third imposes robustness on the inherent quantum and emerging
classical uncertainties. All three methods lead to localized Gaussian pointer
states, their formation and diffusion being governed by well-defined quantum
Langevin equations.Comment: 5 pages, final versio
Complete parameterization, and invariance, of diffusive quantum trajectories for Markovian open systems
The state matrix for an open quantum system with Markovian evolution
obeys a master equation. The master equation evolution can be unraveled into
stochastic nonlinear trajectories for a pure state , such that on average
reproduces . Here we give for the first time a complete
parameterization of all diffusive unravelings (in which evolves
continuously but non-differentiably in time). We give an explicit measurement
theory interpretation for these quantum trajectories, in terms of monitoring
the system's environment. We also introduce new classes of diffusive
unravelings that are invariant under the linear operator transformations under
which the master equation is invariant. We illustrate these invariant
unravelings by numerical simulations. Finally, we discuss generalized gauge
transformations as a method of connecting apparently disparate descriptions of
the same trajectories by stochastic Schr\"odinger equations, and their
invariance properties.Comment: 10 pages, including 5 figures, submitted to J. Chem Phys special
issue on open quantum system
Classical-Quantum Coexistence: a `Free Will' Test
Von Neumann's statistical theory of quantum measurement interprets the
instantaneous quantum state and derives instantaneous classical variables. In
realty, quantum states and classical variables coexist and can influence each
other in a time-continuous way. This has been motivating investigations since
longtime in quite different fields from quantum cosmology to optics as well as
in foundations. Different theories (mean-field, Bohm, decoherence, dynamical
collapse, continuous measurement, hybrid dynamics, e.t.c.) emerged for what I
call `coexistence of classical continuum with quantum'. I apply to these
theories a sort of `free will' test to distinguish `tangible' classical
variables useful for causal control from useless ones.Comment: 7pp, based on talk at Conf. on Emergent Quantum Mechanics, Heinz von
Foerster Congress (Vienna University, Nov 11-13, 2011
The frictional Schr\"odinger-Newton equation in models of wave function collapse
Replacing the Newtonian coupling G by -iG, the Schrodinger-Newton equation
becomes ``frictional''. Instead of the reversible Schrodinger-Newton equation,
we advocate its frictional version to generate the set of pointer states for
macroscopic quantum bodies.Comment: 6pp LaTeX for J.Phys.Conf.Ser.+2 figs. Talk given at the Int.
Workshop DICE2006 "Quantum Mechanics between Decoherence and Determinism: new
aspects from particle physics to cosmology" Piombino, Sept 11-15, 200
Irreversible decay of nonlocal entanglement via a reservoir of a single degree of freedom
Recently, it has been realized that nonlocal disentanglement may take a
finite time as opposite to the asymptotic decay of local coherences. We find in
this paper that a sudden irreversible death of entanglement takes place in a
two atom optical Stern-Gerlach model. In particular, the one degree non
dissipative environment here considered suddenly destroys the initial
entanglement of any Bell's states superposition.Comment: 6 pages, 4 figures, improved presentation, v2: title changed,
references added, accepted for publication in Phys. Rev. A (Fundamental
concepts
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