32,208 research outputs found
Choice of Consistent Family, and Quantum Incompatibility
In consistent history quantum theory, a description of the time development
of a quantum system requires choosing a framework or consistent family, and
then calculating probabilities for the different histories which it contains.
It is argued that the framework is chosen by the physicist constructing a
description of a quantum system on the basis of questions he wishes to address,
in a manner analogous to choosing a coarse graining of the phase space in
classical statistical mechanics. The choice of framework is not determined by
some law of nature, though it is limited by quantum incompatibility, a concept
which is discussed using a two-dimensional Hilbert space (spin half particle).
Thus certain questions of physical interest can only be addressed using
frameworks in which they make (quantum mechanical) sense. The physicist's
choice does not influence reality, nor does the presence of choices render the
theory subjective. On the contrary, predictions of the theory can, in
principle, be verified by experimental measurements. These considerations are
used to address various criticisms and possible misunderstandings of the
consistent history approach, including its predictive power, whether it
requires a new logic, whether it can be interpreted realistically, the nature
of ``quasiclassicality'', and the possibility of ``contrary'' inferences.Comment: Minor revisions to bring into conformity with published version.
Revtex 29 pages including 1 page with figure
Correspondence Truth and Quantum Mechanics
The logic of a physical theory reflects the structure of the propositions
referring to the behaviour of a physical system in the domain of the relevant
theory. It is argued in relation to classical mechanics that the propositional
structure of the theory allows truth-value assignment in conformity with the
traditional conception of a correspondence theory of truth. Every proposition
in classical mechanics is assigned a definite truth value, either 'true' or
'false', describing what is actually the case at a certain moment of time.
Truth-value assignment in quantum mechanics, however, differs; it is known, by
means of a variety of 'no go' theorems, that it is not possible to assign
definite truth values to all propositions pertaining to a quantum system
without generating a Kochen-Specker contradiction. In this respect, the
Bub-Clifton 'uniqueness theorem' is utilized for arguing that truth-value
definiteness is consistently restored with respect to a determinate sublattice
of propositions defined by the state of the quantum system concerned and a
particular observable to be measured. An account of truth of contextual
correspondence is thereby provided that is appropriate to the quantum domain of
discourse. The conceptual implications of the resulting account are traced down
and analyzed at length. In this light, the traditional conception of
correspondence truth may be viewed as a species or as a limit case of the more
generic proposed scheme of contextual correspondence when the non-explicit
specification of a context of discourse poses no further consequences.Comment: 19 page
Quantum value indefiniteness
The indeterministic outcome of a measurement of an individual quantum is
certified by the impossibility of the simultaneous, definite, deterministic
pre-existence of all conceivable observables from physical conditions of that
quantum alone. We discuss possible interpretations and consequences for quantum
oracles.Comment: 19 pages, 2 tables, 2 figures; contribution to PC0
- …