Quantum weirdness? It's all in your mind.

[Nicolaas Vroom]

In Scientific American June 2013 there is an article
about: 'Quantum Weirdness? It's all in your mind'
The article claims that in order to understand
quantum theory ( Schrodingers Cat Paradox) you
do not need standard probabilities but Quantum
Bayesianism.
In the article is written:
'By insisting that the wave function is a subjective
propertry of the observer, rather than an
objective property of the cat in the box, QBism
eliminates the puzzle.'
IMO such a sentence is not clear.
The whole paradox of Schrodingers Cat is about the
half live time of a radio active element.
To measure that time you have to count 100 decays
and measure the time that it takes.
If this time is 100 seconds than you now that if you
start again this experiment and you stop the experiment
after 1 second than you know that there is 50% chance
that the element did not decay.
I do not know what such an experiment has to do
with anything that is in MY mind nor in the mind of
any human being (observer)
The whole point is that you must stop the experiment
exactly after one second other wise the outcome
of the experiment will be different (performed 100
times identical)

For a full review of the article read this:
http://users.telenet.be/nicvroom/ScientificAm%20June%202013.htm

Nicolaas Vroom
http://users.pandora.be/nicvroom/

[Tom Roberts]

On 6/6/13 6/6/13 - 2:09 AM, Nicolaas Vroom wrote:
> The whole paradox of Schrodingers Cat is about the

> half live time of a radio active element.[...]

Not really. Measuring radioactive half lives is clear and well defined.

The real paradox supposedly is: is the cat alive or dead, or in some sort of
"superposition"?

I think this is resolved by realizing that QM is a MODEL of a certain
portion of the world, with a limited domain of validity. Cats, and this
question about them, are FAR outside that domain. So the "paradox" is
ill posed.

Indeed, I think this is essentially the same mistake made by the
Catholic Church in persecuting Copernicus, Galileo, Darwin, et al:
assuming a model has universal validity, when its actual domain is
rather limited. (Of course the Church claimed "universal truth", which
is merely the same mistake writ large.)

Tom Roberts

[JohnF]

You might also want to see David Mermin's Commentary column in
the July 2012 issue of Physics Today, at
http://www.physicstoday.org/resource/1/phtoad/v65/i7/p8_s1?bypassSSO=1

In fact, I posted a similarly-minded question to spr back then...
To quote the part [of Mermin's commentary] I'm asking a question about,
QBism immediately disposes of the paradox of "Wigner's friend."
The friend makes a measurement in a closed laboratory, notes
the outcome, and assigns a state corresponding to that outcome.
Wigner, outside the door, doesn't know the outcome and assigns
the friend, the apparatus, and the system an entangled state
that superposes all possible outcomes. Who is right?
For the QBist, both are right: The friend assigns a state
incorporating her experience; Wigner assigns a state incorporating
his. Quantum state assignments, like probability assignments,
are relative to the agent who makes them.
I'm sure Mermin's right and I'm wrong, but the above seems wrong
to me: the friend's objectively right and Wigner's wrong, as follows.
Suppose the friend makes a p(rojection)vm that throws the system
into a nice eigenstate of that observable. Then we know a second
measurement will result in the same outcome with probablility 1.
And the friend's state assignment correctly predicts that, whereas
Wigner's doesn't. So isn't the friend right and Wigner wrong?
Apparently not, since I doubt Mermin could've missed that.
So I must be missing something: how is it that "both are right"?

Nobody [else] answered that, but Stephen Parrott subsequently replied...
I was surprised that no one answered your question, so I will try.
At first I intended to send this just to you, but then I decided that
its main point, though elementary, is rather fundamental and
might possibly have wider interest.
Neither Wigner nor his friend are "right" about what is the (quantum)
state. They have different states corresponding to their different
information about the system.
This is essentially a classical effect which has nothing to
do with quantum theory. It has to hold in any sensible probabilistic
theory in which not all observers have complete information.
To give an explicit example, suppose that both Wigner and his
friend know that the state of the system in the laboratory is initially
the *pure* state ( | e > + | f > ) / \sqrt{2} where | e >, | f > is
an orthonormal basis of quantum states.
Suppose the friend measures in this basis obtaining state | e >
with probability 1/2 and | f > with probability 1/2.
Suppose the friend tells Wigner that he has made that measurement,
but he does not reveal the result. Then the friend's state
is either | e > or | f >, but Wigner's state is the *mixed* state which
is | e > with probability 1/2 and | f > with probability 1/2.
The same would hold for *any* probabilistic theory
(not just quantum theory) in which the laboratory measurement had
to result in just one of two possibilities..
I read Mermin's comment (and basically agree) as pointing out that
Bayesian probabilistic ideas have to be a fundamental part of quantum
theory (and indeed of any nontrivial probabilistic theory, though he
does not point this out).
Hope that helps, Stephen Parrott
--
John Forkosh ( mailto: j...@f.com where j=john and f=forkosh )

[Thomas Cuny]

On Thursday, June 6, 2013 2:09:26 AM UTC-5, Nicolaas Vroom wrote:
> In Scientific American June 2013 there is an article
> about: 'Quantum Weirdness? It's all in your mind'
> The article claims that in order to understand
> quantum theory ( Schrodingers Cat Paradox) you
> do not need standard probabilities but Quantum
> Bayesianism.

Schrodingers Cat Paradox occurs for the same reason that planets sometimes
go backward in their orbits. The observers frame of reference is broken.

[Jos Bergervoet]

[ The following text is in the "ISO-8859-1" character set. ]
[ Your display is set for the "US-ASCII" character set. ]
[ Some characters may be displayed incorrectly. ]

On 6/6/2013 9:09 AM, Nicolaas Vroom wrote:
> In Scientific American June 2013 there is an article
> about: 'Quantum Weirdness? It's all in your mind'

This title could apply to any difficult puzzle..

...

> In the article is written:
> 'By insisting that the wave function is a subjective
> propertry of the observer, rather than an
> objective property of the cat in the box, QBism
> eliminates the puzzle.'
> IMO such a sentence is not clear.

It has no meaning. Every theory about the world
is in our mind. Whether it gives us good results
or bad results, it can always be called subjective
(and all observations as well, for that matter.)

In the example of QM, we have the concept of
"subjective collapse" of the wave function. But
also there, the adjective is meaningless. The
concept is about how disentanglement will make
subspaces of a vector space *almost* invariant
under time evolution. Which means that it could
better be called "effective" collapse. It's a
mathematical property of a theory and it can be
mathematically checked whether a certain theory
has this property or not. It's therefore even
quite "objective", in my view.

Using the term "subjective" in QM is pushing
at an open door, not only since all theories are
in our mind, but even if one wants to stress that
it gives different pictures for different observers,
because a simple thing like standing on a different
place on the ground will also do that.

Probably what people mean by it is that in quantum
theory there are new, once unexpected, degrees of
freedom (the disentangled states) which can give you
a different view of the world even without having
to stand on a different place on the ground! So the
theory has some extra complexity and some unexpected
properties. People will call that "subjective" or
"weird" but that all just means they don't like the
theory.

--
Jos

[Gregor Scholten]

Am 09.06.2013 09:54, schrieb Tom Roberts:

> The real paradox supposedly is: is the cat alive or dead, or in some sort of
> "superposition"?
>
> I think this is resolved by realizing that QM is a MODEL of a certain
> portion of the world, with a limited domain of validity. Cats, and this
> question about them, are FAR outside that domain. So the "paradox" is
> ill posed.

the trouble with this "solution" is that it implies that quantum theory
is an incomplete theory because it does not say anything about things
outside the domain you are talking about. So this implies that another
theory is required that completes quantum theory.

> Indeed, I think this is essentially the same mistake made by the
> Catholic Church in persecuting Copernicus, Galileo, Darwin, et al:
> assuming a model has universal validity, when its actual domain is
> rather limited.

this is a good analogy: the incompleteness of the model opined by the
church implied requirement of a new model - in case of Copernicus and
Galilei the heliocentric model. What is this new model in case of
quantum theory?

[Nicolaas Vroom]

Op zondag 9 juni 2013 09:54:59 UTC+2 schreef Tom Roberts het volgende:

> On 6/6/13 6/6/13 - 2:09 AM, Nicolaas Vroom wrote:
>
> > The whole paradox of Schrodingers Cat is about the
> > half live time of a radio active element.[...]
>
> Not really. Measuring radioactive half lives is clear and well defined.
> The real paradox supposedly is: is the cat alive or dead, or in some sort
> of "superposition"?

I agree with: half lives is well defined. That means IMO you can remove
the cat from the experiment and rephrase the paradox: "The paradox is:
is the element decayed or not decayed, or in some sort of superposition
(i.e being both decayed and not decayed)" IMO the concept superposition
does not make sense because it is based on lack of my personal knowledge
and personal knowledge has nothing to do with science.

Nicolaas Vroom
http://users.pandora.be/nicvroom/

[Sylvia Else]

On 9/06/2013 5:54 PM, Tom Roberts wrote:
> On 6/6/13 6/6/13 - 2:09 AM, Nicolaas Vroom wrote:
>> The whole paradox of Schrodingers Cat is about the
>> half live time of a radio active element.[...]
>
> Not really. Measuring radioactive half lives is clear and well defined.
>
> The real paradox supposedly is: is the cat alive or dead, or in some sort of
> "superposition"?
>
> I think this is resolved by realizing that QM is a MODEL of a certain
> portion of the world, with a limited domain of validity. Cats, and this
> question about them, are FAR outside that domain. So the "paradox" is
> ill posed.
>

I prefer the view that it's inconsistent to worry about the cat being in
a superpostion of being alive or dead, but to ignore the possibility
that the observer is in a superposition of being near an alive cat and
being near a dead cat.

Sylvia

[Jonathan Thornburg [remove -animal to reply]]

JohnF <jo...@please.see.sig.for.email.com> wrote:
> You might also want to see David Mermin's Commentary column in
> the July 2012 issue of Physics Today, at
> http://www.physicstoday.org/resource/1/phtoad/v65/i7/p8_s1?bypassSSO=1

For anyone who hasn't already read it, David Mermin (a.k.a. N. David Mermin)
also wrote a *superb* Physics Today article on this topic almost 30 years
ago:
N. David Mermin
"Is the moon there when nobody looks?
Reality and the quantum theory"
Physics Today volume 38, April 1985, pages 38-47
A reformatted version of this is available at
http://www.iafe.uba.ar/e2e/phys230/history/moon.pdf

I *highly* recommend this article.

I think it was Feynman who famously said in a talk at UC Santa Barbara
"Deep down, nobody understands quantum mechanics". Perhaps this phrase
should be known as the "Santa Barbara interpretation" of quantum mechanics?

--
-- "Jonathan Thornburg [remove -animal to reply]" <jth...@astro.indiana-zebra.edu>
Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA
on sabbatical in Canada through September 2013
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
-- quote by Freire / poster by Oxfam

[Gregor Scholten]

Am 09.06.2013 22:27, schrieb Sylvia Else:

> I prefer the view that it's inconsistent to worry about the cat being in
> a superpostion of being alive or dead, but to ignore the possibility
> that the observer is in a superposition of being near an alive cat and
> being near a dead cat.

so you propose the many worlds interpretation?

[Nicolaas Vroom]

Op zondag 9 juni 2013 09:55:42 UTC+2 schreef Thomas Cuny het volgende:

The reason that planets sometimes seem to move backwards comes
because we take the earth (our position) as a reference point
which in turn moves around the sun.
When we do science we should do that independent of any human
involvement as clearly as possible.

IMO the same problem exists with the Schrodinger Cat Paradox.
My personal interpretation of the state of the cat is not important.
What counts are the results of experiments which every body
can repeat which the same results.
There is nothing wrong in an experiment with two people two kilometers
away from each other when one measured A that the other one measures
non A (or reverse). It becomes tricky when it that case it is supposed
that faster than light speed communication is involved.

Nicolaas Vroom
http://users.pandora.be/nicvroom/

[Nicolaas Vroom]

Op zondag 9 juni 2013 22:27:29 UTC+2 schreef Jonathan Thornburg:

> JohnF <jo...@please.see.sig.for.email.com> wrote:
> > You might also want to see David Mermin's Commentary column
> > in the July 2012 issue of Physics Today, at
> > http://www.physicstoday.org/resource/1/phtoad/v65/i7/p8_s1?bypassSSO=1
>
> For anyone who hasn't already read it, David Mermin (a.k.a.
> N. David Mermin) also wrote a *superb* Physics Today article
> on this topic almost 30 years ago:
> N. David Mermin
> "Is the moon there when nobody looks?
> Reality and the quantum theory"
> Physics Today volume 38, April 1985, pages 38-47
> A reformatted version of this is available at
> http://www.iafe.uba.ar/e2e/phys230/history/moon.pdf
>
> I *highly* recommend this article.

The article is partly based on a thought experiment and
as such it describes the result of an experiment which
IMO takes place in our head.
Of course you can do that but IMO that includes a risk
because it does mean that the results of such an imaginary
experiment is equal to (can be compared with) a real
experiment which tries to do the same.
An real experiment by Alain Aspect is discussed but not
the detailed results of what is measured.
The article is also not clear if in order to understand
real experiments (or the physical reality)
action at a distance or superluminal velocity is required.
IMO when I study the thought experiment the answer
is no.
For more detail of my reasoning read this:
http://users.telenet.be/nicvroom/David%20Mermin.htm

Nicolaas Vroom

[Kalmia Latifolia]

"Tom Roberts" <tjrobe...@sbcglobal.net> wrote in message
news:Cr-dna42np6...@giganews.com...

The Catholic Church did persecute Copernicus and .... Darwin?

Very interesting.

[Anon E. Mouse]

[[Mod. note -- Please limit your text to fit within 80 columns,
preferably around 70, so that readers don't have to scroll horizontally
to read each line. I have manually reformatted this article. -- jt]]

On Thursday, June 6, 2013 2:09:26 AM UTC-5, Nicolaas Vroom wrote:

When a coin is flipped it comes up either heads or tails. This is
a property of the coin, based on its geometry. The observation of
either a head or tail outcome after a given flip can be thought of
as a property of the observer.

Similarly, a decay typically emits a detectable partcle wave. This
is a property of atomic nuclei . The observation of this event is
a property of the detector. Unless a weak measure is used, then the
detector itself siwill absorb this and in the process destroy the
signal. This means that subsequent detections are typically not
influenced by preceeding detections.

The presumption that the observation of a coin coming up heads will
have no influence of the next flip is a property of statistics.

Entanglement in particle physics deals with the issue of whether
an atom is a "fair coin" or not. Often particle phusics events are
not fair coins. To give a specific example related to Schrodinger's
cat, If the decaying sample is quite small then the depletion of
the decaying isotope will cause the measured rate of decay to
decrease. This effect is fundamental to the definition of halflife.
Other forms of quantum entanglement are more complex and therefor
more interesting but they are not fundamentally different than this
simple example.

Historically, the statistical evidence that there was entanglement
led to "pair production" rules . However, these exceptions to the
fair coin rule did not fundamentally alter the quasi random nature
of particle physic events. As a specific example, some decays seem
to be triggered by nuetron collisions, while others seem to have
no particular specific causual event associated with a specific
decay.

AAG

[Surfer]

On Sun, 09 Jun 2013 10:28:34 PDT, Gregor Scholten <g.sch...@gmx.de>
wrote:

A model that incorporates a theory of wave function collapse might
turn out to be a viable successor.

Eg.

Parameter Diagrams of the GRW and CSL Theories of Wave Function
Collapse
William Feldmann, Roderich Tumulka
J. Phys. A: Math. Theor. 45 (2012) 065304
http://arxiv.org/abs/1109.6579

Abstract: It has been hypothesized that the time evolution of wave
functions might include collapses, rather than being governed by the
Schroedinger equation. The leading models of such an evolution, GRW
and CSL, both have two parameters (or new constants of nature), the
collapse width sigma and the collapse rate lambda. We draw a diagram
of the sigma-lambda-plane showing the region that is empirically
refuted and the region that is philosophically unsatisfactory.


(Which in the above paper leaves a region that is neither empirically
refuted nor philosophically unsatisfactory.)

[krysti...@gmail.com]

On Thursday, June 6, 2013 3:09:26 AM UTC-4, Nicolaas Vroom wrote:
> In Scientific American June 2013 there is an article
>
> about: 'Quantum Weirdness? It's all in your mind'
>
> The article claims that in order to understand
>
> quantum theory ( Schrodingers Cat Paradox) you
>
> do not need standard probabilities but Quantum
>
> Bayesianism.

It was a joke, science, come on, it's been years now! Schr?dinger
was trying to illustrate how ridiculous the Copenhagen (Bohr) version
of of quantum superposition was: that a state itself was created
by the act of human observation.

It had nothing to do with the reality of a cat, a box, or a radioactive
element, or even the poison waiting to be released. It was an analogy
ad absurdum.