II. THE ACQUISITION OF INFORMATION
A. The ambivalent quantum observer
Quantum mechanics is used by theorists in two different
ways. It is a tool for computing accurate relationships
between physical constants, such as energy levels,
cross sections, transition rates, etc. These calculations
are technically difficult, but they are not controversial.
In addition to this, quantum mechanics also provides
statistical predictions for results of measurements performed
on physical systems that have been prepared in a
specified way.
[My comment #5: No mention of Yakir Aharonov's intermediate present "weak measurements"
with both history past pre-selection and destiny future post-selection constraints. The latter in
Wheeler delayed choice mode would force the inference of real back-from-the-future retrocausality.
This would still be consistent with Abner Shimony's "passion at a distance," i.e. "signal locality"
in that the observer at the present weak measurement would not know what the future constraint
actually will be. In contrast, with signal non locality (Sarfatti 1976 MIT Tech Review (Martin Gardner) &
Antony Valentini (2002)) such spooky precognition would be possible as in Russell Targ's reports on
CIA funded RV experiments at SRI in the mid 70's and 80's.
This is, on the face of it, a gross violation of orthodox
quantum theory as laid out here in the Peres review paper.]
The quantum measuring process is the interface
of classical and quantum phenomena. The preparation
and measurement are performed by macroscopic
devices, and these are described in classical terms. The
necessity of using a classical terminology was emphasized
by Niels Bohr (1927) from the very early days of
quantum mechanics. Bohr’s insistence on a classical description
was very strict. He wrote (1949)
‘‘ . . . by the word ‘experiment’ we refer to a situation
where we can tell others what we have done and what
we have learned and that, therefore, the account of the
experimental arrangement and of the results of the observations
must be expressed in unambiguous language,
with suitable application of the terminology of
classical physics.’’
Note the words ‘‘we can tell.’’ Bohr was concerned
with information, in the broadest sense of this term. He
never said that there were classical systems or quantum
systems. There were physical systems, for which it was
appropriate to use the classical language or the quantum
language. There is no guarantee that either language
gives a perfect description, but in a well-designed experiment
it should be at least a good approximation.
Bohr’s approach divides the physical world into ‘‘endosystems’’
(Finkelstein, 1988), which are described by
quantum dynamics, and ‘‘exosystems’’ (such as measuring
apparatuses), which are not described by the dynamical
formalism of the endosystem under consideration.
A physical system is called ‘‘open’’ when parts of
the universe are excluded from its description. In different
Lorentz frames used by observers in relative motion,
different parts of the universe may be excluded. The
systems considered by these observers are then essentially
different, and no Lorentz transformation exists
that can relate them (Peres and Terno, 2002).
It is noteworthy that Bohr never described the measuring
process as a dynamical interaction between an
exophysical apparatus and the system under observation.
He was, of course, fully aware that measuring apparatuses
are made of the same kind of matter as everything
else, and they obey the same physical laws. It is
therefore tempting to use quantum theory in order to
investigate their behavior during a measurement. However,
if this is done, the quantized apparatus loses its
status as a measuring instrument. It becomes a mere intermediate
system in the measuring process, and there
must still be a final instrument that has a purely classical
description (Bohr, 1939).
Measurement was understood by Bohr as a primitive
notion. He could thereby elude questions which caused
considerable controversy among other authors. A
quantum-dynamical description of the measuring process
was first attempted by John von Neumann in his
treatise on the mathematical foundations of quantum
theory (1932). In the last section of that book, as in an
afterthought, von Neumann represented the apparatus
by a single degree of freedom, whose value was correlated
with that of the dynamical variable being measured.
Such an apparatus is not, in general, left in a definite
pure state, and it does not admit a classical
description. Therefore von Neumann introduced a second
apparatus which observes the first one, and possibly
a third apparatus, and so on, until there is a final measurement,
which is not described by quantum dynamics
and has a definite result (for which quantum mechanics
can give only statistical predictions). The essential point
that was suggested, but not proved by von Neumann, is
that the introduction of this sequence of apparatuses is
irrelevant: the final result is the same, irrespective of the
location of the ‘‘cut’’ between classical and quantum
physics.8
These different approaches of Bohr and von Neumann
were reconciled by Hay and Peres (1998), who
8At this point, von Neumann also speculated that the final
step involves the consciousness of the observer—a bizarre
statement in a mathematically rigorous monograph (von Neumann,
1955).
B. The measuring process
Dirac (1947) wrote that ‘‘a measurement always
causes the system to jump into an eigenstate of the dynamical
variable being measured.’’ Here, we must be
careful: a quantum jump (also called a collapse) is something
that happens in our description of the system, not
to the system itself. Likewise, the time dependence of
the wave function does not represent the evolution of a
physical system. It only gives the evolution of probabilities
for the outcomes of potential experiments on that
system (Fuchs and Peres, 2000).
Let us examine more closely the measuring process.
First, we must refine the notion of measurement and
extend it to a more general one: an intervention. An
intervention is described by a set of parameters which
include the location of the intervention in spacetime, referred
to an arbitrary coordinate system. We also have
to specify the speed and orientation of the apparatus in
the coordinate system that we are using as well as various
other input parameters that control the apparatus,
such as the strength of a magnetic field or that of a rf
pulse used in the experiment. The input parameters are
determined by classical information received from past
interventions, or they may be chosen arbitrarily by the
observer who prepares that intervention or by a local
random device acting in lieu of the observer.
[My comment #6: Peres, in my opinion, makes another mistake.
Future interventions will affect past weak measurements.
Back From the Future
A series of quantum experiments shows that measurements performed in the future can influence the present. Does that mean the universe has a destiny—and the laws of physics pull us inexorably toward our prewritten fate?
http://discovermagazine.com/2010/apr/01-back-from-the-future#.UieOnhac5Hw ]
An intervention has two consequences. One is the acquisition
of information by means of an apparatus that
produces a record. This is the ‘‘measurement.’’ Its outcome,
which is in general unpredictable, is the output of
the intervention. The other consequence is a change of
the environment in which the quantum system will
evolve after completion of the intervention. For example,
the intervening apparatus may generate a new
Hamiltonian that depends on the recorded result. In particular,
classical signals may be emitted for controlling
the execution of further interventions. These signals are,
of course, limited to the velocity of light.
The experimental protocols that we consider all start
in the same way, with the same initial state ... , and the
first intervention is the same. However, later stages of
the experiment may involve different types of interventions,
possibly with different spacetime locations, depending
on the outcomes of the preceding events. Yet,
assuming that each intervention has only a finite number
of outcomes, there is for the entire experiment only a
finite number of possible records. (Here, the word
record means the complete list of outcomes that occurred
during the experiment. We do not want to use the
word history, which has acquired a different meaning in
the writings of some quantum theorists.)
Each one of these records has a definite probability in
the statistical ensemble. In the laboratory, experimenters
can observe its relative frequency among all the records
that were obtained; when the number of records tends
to infinity, this relative frequency is expected to tend to
the true probability. The aim of theory is to predict the
probability of each record, given the inputs of the various
interventions (both the inputs that are actually controlled
by the local experimenter and those determined
by the outputs of earlier interventions). Each record is
objective: everyone agrees on what happened (e.g.,
which detectors clicked). Therefore, everyone agrees on
what the various relative frequencies are, and the theoretical
probabilities are also the same for everyone.
Interventions are localized in spacetime, but quantum
systems are pervasive. In each experiment, irrespective
of its history, there is only one quantum system, which
may consist of several particles or other subsystems, created
or annihilated at the various interventions. Note
that all these properties still hold if the measurement
outcome is the absence of a detector click. It does not
matter whether this is due to an imperfection of the detector
or to a probability less than 1 that a perfect detector
would be excited. The state of the quantum system
does not remain unchanged. It has to change to
respect unitarity. The mere presence of a detector that
could have been excited implies that there has been an
interaction between that detector and the quantum system.
Even if the detector has a finite probability of remaining
in its initial state, the quantum system correlated
to the latter acquires a different state (Dicke,
1981). The absence of a click, when there could have
been one, is also an event.
…
The measuring process involves not only the physical
system under study and a measuring apparatus (which
together form the composite system C) but also their
environment, which includes unspecified degrees of freedom
of the apparatus and the rest of the world. These
unknown degrees of freedom interact with the relevant
ones, but they are not under the control of the experimenter
and cannot be explicitly described. Our partial
ignorance is not a sign of weakness. It is fundamental. If
everything were known, acquisition of information
would be a meaningless concept.
A complete description of C involves both macroscopic
and microscopic variables. The difference between
them is that the environment can be considered as
adequately isolated from the microscopic degrees of
freedom for the duration of the experiment and is not
influenced by them, while the environment is not isolated
from the macroscopic degrees of freedom. For example,
if there is a macroscopic pointer, air molecules bounce
from it in a way that depends on the position of that
pointer. Even if we can neglect the Brownian motion of
a massive pointer, its influence on the environment leads
to the phenomenon of decoherence, which is inherent to
the measuring process.
An essential property of the composite system C,
which is necessary to produce a meaningful measurement,
is that its states form a finite number of orthogonal
subspaces which are distinguishable by the observer.
[My comment #7: This is not the case for Aharonov's weak measurements where
<A>weak = <history|A|destiny>/<history|destiny>
Nor is it true when Alice's orthogonal micro-states are entangled with Bob's far away distinguishably non-orthogonal macro-quantum Glauber coherent and possibly squeezed states.
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en.wikipedia.org/wiki/Coherent_states
In physics, in quantum mechanics, a coherent state is the specific quantum state of the quantum harmonic oscillator whose dynamics most closely resembles the ...
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Dec 8, 2011 - Abstract: We review entangled coherent state research since its first implicit use in 1967
|Alice,Bob> = (1/2)[|Alice +1>|Bob alpha> + |Alice -1>|Bob beta>]
<Alice+1|Alice -1> = 0
<Bob alpha|Bob beta> =/= 0
e.g. Partial trace over Bob's states |<Alice +1|Alice-Bob>|^2 = (1/2)[1 + |<Bob alpha|Bob beta>|^2] > 1
this is formally like a weak measurement where the usual Born probability rule breaks down.
Complete isolation from environmental decoherence is assumed here.
It is clear violation of "passion at a distance" no-entanglement signaling arguments based on axioms that are empirically false in my opinion.
"The statistics of Bob’s result are not affected at all by what Alice may simultaneously do somewhere else. " (Peres)
is false.
While a logically correct formal proof is desirable in physics, Nature has ways of leap frogging over their premises.
One can have constrained pre and post-selected conditional probabilities that are greater than 1, negative and even complex numbers.
All of which correspond to observable effects in the laboratory - see Aephraim Steinberg's experimental papers
University of Toronto.]
Each macroscopically distinguishable subspace corresponds
to one of the outcomes of the intervention and
defines a POVM element Em , given explicitly by Eq. (8)
below. …
C. Decoherence
Up to now, quantum evolution is well defined and it is
in principle reversible. It would remain so if the environment
could be perfectly isolated from the macroscopic
degrees of freedom of the apparatus. This demand is of
course self-contradictory, since we have to read the result
of the measurement if we wish to make any use of it.
A detailed analysis of the interaction with the environment,
together with plausible hypotheses (Peres, 2000a),
shows that states of the environment that are correlated
with subspaces of C with different labels m can be treated
as if they were orthogonal. This is an excellent approximation
(physics is not an exact science, it is a science of
approximations). The resulting theoretical predictions
will almost always be correct, and if any rare small deviation
from them is ever observed, it will be considered
as a statistical quirk or an experimental error.
The density matrix of the quantum system is thus effectively
block diagonal, and all our statistical predictions
are identical to those obtained for an ordinary mixture
of (unnormalized) pure states
….
This process is called decoherence. Each subspace
m is stable under decoherence—it is their relative
phase that decoheres. From this moment on, the macroscopic
degrees of freedom of C have entered into the
classical domain. We can safely observe them and ‘‘lay
on them our grubby hands’’ (Caves, 1982). In particular,
they can be used to trigger amplification mechanisms
(the so-called detector clicks) for the convenience of the
experimenter.
Some authors claim that decoherence may provide a
solution of the ‘‘measurement problem,’’ with the particular
meaning that they attribute to that problem
(Zurek, 1991). Others dispute this point of view in their
comments on the above article (Zurek, 1993). A reassessment
of this issue and many important technical details
were recently published by Zurek (2002, 2003). Yet
decoherence has an essential role, as explained above. It
is essential that we distinguish decoherence, which results
from the disturbance of the environment by the
apparatus (and is a quantum effect), from noise, which
would result from the disturbance of the system or the
apparatus by the environment and would cause errors.
Noise is a mundane classical phenomenon, which we ignore
in this review.
E. The no-communication theorem
We now derive a sufficient condition that no instantaneous
information transfer can result from a distant intervention.
We shall show that the condition is
[Amm ,Bnn] = 0
where Amm and Bnn are Kraus matrices for the observation
of outcomes m by Alice and n by Bob.
[My comment #8: "The most beautiful theory is murdered by an ugly fact." - Feynman
e.g. Libet-Radin-Bierman presponse in living brain data
SRI CIA vetted reports of remote viewing by living brains.
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www.biomindsuperpowers.com/Pages/CIA-InitiatedRV.html
As if to add insult to injury, he then went on to "remote view" the interior of the apparatus, .... Figure 6 - Left to right: Christopher Green, Pat Price, and Hal Puthoff.
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en.wikipedia.org/wiki/Harold_E._Puthoff
Puthoff, Hal, Success Story, Scientology Advanced Org Los Angeles (AOLA) special... H. E. Puthoff, CIA-Initiated Remote Viewing At Stanford Research Institute, ...
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en.wikipedia.org/wiki/Remote_viewing
Among some of the ideas that Puthoff supported regarding remote viewing was the ...by Russell Targ and Hal Puthoff at Stanford Research Institute in the 1970s ...
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www.youtube.com/watch?v=FOAfH1utUSM
Apr 28, 2011 - Uploaded by corazondelsur
Dr. Hal Puthoff is considered the father of the US government'sRemote Viewing program, which reportedly ...
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www.remoteviewed.com/remote_viewing_halputhoff.htm
Dr. Harold E. Puthoff is Director of the Institute for Advanced Studies at Austin. A theoretical and experimental physicist specializing in fundamental ...