15,501 research outputs found
Relativistic generalizations of gravity-induced localization models
Nonunitary versions of Newtonian gravity leading to wavefunction localization
admit natural special-relativistic generalizations. They include the first
consistent relativistic localization models. At variance with the unified model
of localization and gravity, the purely localizing version requires negative
energy fields, which however are less harmful than usual and can be used to
build ultraviolet-finite theories.Comment: RevTex, 10 page
Entropic localization in non-unitary Newtonian gravity
The localizing properties and the entropy production of the Newtonian limit
of a nonunitary version of fourth order gravity are analyzed. It is argued that
pure highly unlocalized states of the center of mass motion of macroscopic
bodies rapidly evolve into unlocalized ensembles of highly localized states.
The localization time and the final entropy are estimated
Quantum Computation using Decoherence-Free States of the Physical Operator Algebra
The states of the physical algebra, namely the algebra generated by the
operators involved in encoding and processing qubits, are considered instead of
those of the whole system-algebra. If the physical algebra commutes with the
interaction Hamiltonian, and the system Hamiltonian is the sum of arbitrary
terms either commuting with or belonging to the physical algebra, then its
states are decoherence free. One of the considered examples shows that, for a
uniform collective coupling to the environment, the smallest number of physical
qubits encoding a decoherence free logical qubit is reduced from four to three.Comment: 16 pages, LATEX/REVTEX, expanded version to appear in Phys. Rev.
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