Super Copenhagen Interpretation (Consistent Histories)

Hi,

What can you say about the QM Consistent Histories interpretation.
Do you agree with it or not and why?

http://quantum.phys.cmu.edu/CHS/quest.html

What is the relationship of consistent histories and standard
quantum mechanics (as found in textbooks)?

Consistent histories is standard quantum mechanics presented in a
coherent fashion with the ambiguities and lack of clarity found
in the usual textbook presentations replaced with a clear set of
logical rules and principles for reasoning about a quantum
system. It is, in brief, "Copenhagen done right." There is, to be
sure, more that can be said - see the following questions.

What is the role of measurements in standard quantum mechanics
and in consistent histories?

In textbook quantum theory measurements are used to introduce
probabilities into the theory, and this feature is the source of
many conceptual difficulties and paradoxes. In particular, it
gives the misleading impression that one cannot apply statistical
ideas to quantum processes in the absence of measuring devices,
e.g., to the decay of unstable particles in the center of the
sun, or in interstellar space. In addition, a great deal of
fruitless effort has been expended in an effort to resolve the
quantum "measurement problem" that arises when one wants to treat
the measuring apparatus itself as a quantum system.

By contrast, in the consistent histories approach probabilities
are introduced as part of the axiomatic foundations of quantum
theory, with no necessary connection with measurements. Quantum
dynamical processes are inherently stochastic, and the
probabilities can be calculated using a generalization of the
rule originally introduced by Born. Because it does not employ
measurement as a fundamental principle, the consistent histories
approach allows one to analyze, from a fully quantum-mechanical
perspective, what actually goes on in a physical measurement
process. For example, one can show that a properly constructed
measuring apparatus will reveal a property that the measured
system had before the measurement, and might well have lost
during the measurement process. The probabilities calculated for
measurement outcomes (pointer positions) are identical to those
obtained by the usual rules found in textbooks. What is different
is that by employing suitable families of histories one can show
that m easurements a ctually measure something that is there,
rather than producing a mysterious collapse of a wave function

<snip>

http://quantum.phys.cmu.edu/CHS/histories.html

Brief Introduction to Consistent (Decoherent) Histories

Modern quantum mechanics is based upon two distinct ideas. One is
that wave functions develop in time according to the equation
invented in 1926 by Erwin Schr"dinger. The other is that wave
functions can be used to calculate probabilities, an idea first
proposed, also in 1926, by Max Born. Combining these two ideas in
a consistent way has turned out to be difficult. The approach
found in many textbooks, in which a wave function is used to
calculate the probability that a measurement carried out on some
quan tum system will yield a particular outcome, is not very
satisfactory, for two reasons. First, one often wants to apply
quantum theory to situations which do not involve a measuring
apparatus; for example, in the center of the sun. Second, all
real measuring instruments are themselves made up of quantum
particles, and should therefore be described in quantum terms.
But trying to do so gives rise to difficulties and
inconsistencies in an approach to quantum theory that is based in
essential way upon the conce pt of a measurement.

The consistent histories approach combines wave functions and
probabilities in a fully consistent way which does not rely upon
the use of measurements. It was first proposed by Robert
Griffiths in 1984, and further developed by Roland Omn?s in 1988,
and by Murray Gell-Mann and James Hartle, who used the term
``decoherent histories'', in 1990. A history is a sequence of
quantum events (i.e., wave functions) at successive times.
Probabilities can be assigned to histories provided certain
consistency condition s are satisfied. Histories can be used to
describe how a particle interacts with a measuring apparatus, and
how the outcome of a measurement (e.g., the position of a
pointer) is related to some property of the particle before the
measurement took place. However, they can also be employed for a
single particle, or any number of particles, in the absence of
any measurement. For example, by using consistent histories it is
possible to assign a probability for the time at which an
unstable particle, such as a r adioactive atom, will decay, even
if it is out in interstellar space far from any measuring device.
Consistent histories can be used to analyze various quantum
paradoxes, such as the interference produced by a particle
passing through a double slit, or the correlated pair of
particles considered by Einstein, Podolksy, and Rosen. This
allows the paradox to be understood in quantum terms, without any
need to invoke peculiar long-range influences or other ghostly
effects. The consistent histories approach has also been employed
to analyze prob lems in quantum computation and quantum
cryptography.

Book at amazon

http://www.amazon.com/gp/product/0521539293/sr=8-1/qid=1145311842/ref=pd_bbs_1/104-1809248-1583100?%5Fencoding=UTF8

.

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