43 research outputs found
Quelques remarques à propos du problème de la réalité
Un certain temps s’est écoulé depuis l’agréable rencontre qui s’est tenue à Caen, si bien que les idées émises alors par certains d’entre nous ont pu évoluer ou perdre de leur actualité. En ce qui me concerne, il se trouve que la partie essentielle de ma propre contribution d’alors a été publiée dans l’intervalle et, en outre, diverses réflexions m’ont conduit depuis à considérer la question de la réalité sous un nouveau jour. Certaines de ces i..
Equations intégrales non linéaires en théorie quantique des champs: application à la production mésonique des mésons
Decoherence, irreversibility and the selection by decoherence of quantum states with definite probabilities
The problem investigated in this paper is einselection, i. e. the selection
of mutually exclusive quantum states with definite probabilities through
decoherence. Its study is based on a theory of decoherence resulting from the
projection method in the quantum theory of irreversible processes, which is
general enough for giving reliable predictions. This approach leads to a
definition (or redefinition) of the coupling with the environment involving
only fluctuations. The range of application of perturbation calculus is then
wide, resulting in a rather general master equation.
Two distinct cases of decoherence are then found: (i) A ``degenerate'' case
(already encountered with solvable models) where decoherence amounts
essentially to approximate diagonalization; (ii) A general case where the
einselected states are essentially classical. They are mixed states. Their
density operators are proportional to microlocal projection operators (or
``quasi projectors'') which were previously introduced in the quantum
expression of classical properties.
It is found at various places that the main limitation in our understanding
of decoherence is the lack of a systematic method for constructing collective
observables.Comment: 54 page
Decoherence and wave function collapse
The possibility of consistency between the basic quantum principles of
quantum mechanics and wave function collapse is reexamined. A specific
interpretation of environment is proposed for this aim and applied to
decoherence. When the organization of a measuring apparatus is taken into
account, this approach leads also to an interpretation of wave function
collapse, which would result in principle from the same interactions with
environment as decoherence. This proposal is shown consistent with the
non-separable character of quantum mechanics
Mesoscopic superpositions of vibronic collective states of N trapped ions
We propose a scalable procedure to generate entangled superpositions of
motional coherent states and electronic states in N trapped ions. Beyond their
fundamental importance, these states may be of interest for quantum information
processing and may be used in experimental studies of decoherence.Comment: Final version, as published in Physical Review Letters. See also
further developments and applications in quant-ph/020207