
A Twist on Schrödinger's Cat Paradox - mathgenius
https://www.scientificamerican.com/article/this-twist-on-schroedingers-cat-paradox-has-major-implications-for-quantum-theory/
======
lisper
Here are a couple of things that are very rarely explained in QM pedagogy but
which are very helpful in understanding Shroedinger's cat:

1\. The wave function does not exist in physical space, it exists in
_configuration_ space. Configuration space is the same as physical space only
in the one very special case of a single non-entangled particle. The
intuitions of physical space do not generally carry over into the general case
of configuration space.

2\. In order to produce interference you have to split up the wave function
into two pieces and then bring those pieces back together again with a phase
change. But since the wave function exists in configuration space, "bringing
it back together again" becomes increasingly difficult as the number of
entangled degrees of freedom grows. As a practical matter, it is effectively
impossible to do this once the number grows beyond a few hundred (this is why
building quantum computers is hard). But an actual macroscopic observer
consists of O(10^23) degrees of freedom, and is also entangled with their
environment. This is the reason that large systems behave classically and
don't exhibit interference.

3\. Whether or not a system is in a superposition is not a physical fact about
the system, it is a consequence of the measurement you choose to make. A
vertically polarized photon (for example) is in a superposition relative to a
measurement axis rotated away from the polarization axis. For a more
complicated system, the measurement axis, like the wave function itself, is in
_configuration_ space. But we can only do measurements in _physical_ space.
This is the reason that in order to see interference in an entangled system it
is necessary to do multiple physical measurements and look at the correlations
between them. Doing those kinds of measurements on actual macroscopic objects
is _way_ beyond the current state of the art, and may well be impossible even
in principle. But this is the sort of thing that is contemplated in the theory
behind these experiments. This is the reason that single particles are used as
stand-ins for Wigner's friend.

~~~
taneq
Is physical space an actual thing? Or is it just a statistical interpretation
of configuration space?

~~~
zackees
This entire branch of physics is the equivalent of a geo-centric earth model.

Tesla based his entire electric theory on the Aether.

This theory was wrongly suppressed by results of a Michelson Morley
experiment...

[https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_](https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_)

...which failed to measure Aether-Drift because of the fact that it was done
in a basement, and which was later contradicted by Dayton Miller when he
repeated the experiment on a mountain top:

[http://www.orgonelab.org/miller.htm](http://www.orgonelab.org/miller.htm)

This scientific tragedy, likely done by powerful oligarchs, set the
progression of physics back 100 years. We now have fraudulent branch of
particle physics, which has a terrible track record with pretty much every
prediction it has made, and which would be laughed out of the scientific
community if it weren't for the sustained push by the mainstream media to
hammer it into the minds of intellectuals.

We've been told that light has a set speed of propagation, yet time after time
there are articles posted about light exceeding the speed of light for example
gamma ray jets from quasars, which is explained by positing that the space-
time fabric is moving and causing the reference frame containing the light
wave to increase it's speed above the limit.

[https://www.sciencealert.com/faster-than-light-speed-in-
jets...](https://www.sciencealert.com/faster-than-light-speed-in-jets-that-
produce-gamma-ray-bursts)

The media has become so twisted that we now accept completely broken
interpretations such as virtual particles (used to balance equations), string
theory (completely made up and didn't work), multiple universes, time travel
and a smorgasbord of hilarious interpretations from a fundamentally broken
model of physics.

This article is just yet another desperate attempt to patch up this
hilariously outdated physics branch. Einstein physics is on it's way out. And
when it comes crashing down we will replace it with the work of Tesla and we
will move faster in one decade the entire previous 150 years.

~~~
dhosek
Wow, so much pseudo-science and just plain nonsense in one long comment. The
wikipedia article on Orgone,
[https://en.wikipedia.org/wiki/Orgone](https://en.wikipedia.org/wiki/Orgone)
is a good starting place in learning just how goofy these ideas are.

~~~
numlock86
I good friend of me has an esoteric coworker with a strong focus on Orgone
energy and the like. The stories I get to hear and the "research" we do to
read up on that stuff are fun and quite a filler for good and entertaining
evenings.

------
monktastic1
I haven't read the new paper in enough detail to comment, but also mentioned
is the Renner-Frauchiger paper, which Scott Aaronson heartily debunks here:
[https://www.scottaaronson.com/blog/?p=3975](https://www.scottaaronson.com/blog/?p=3975)

The primary error there is one that people can't seem to stop making for some
strange reason: if you don't measure a property X, and instead measure a (non-
commuting) property Y, you are not free to say what X "would have been," and
-- especially egregiously -- to use that to demonstrate a contradiction. There
is no "would have been" in QM. Either you measure it or you don't, and even
after you do, the value becomes invalid after it evolves or a complementary
variable is measured.

Secondly, Wigner's friend was not a single particle. Asking what a single
particle "experienced" only makes sense if you are a panpsychist (or
"panpsychic" as amusingly misspoken in the article). In any case, it has no
bearing on the essence of Wigner's question.

~~~
TheOtherHobbes
I think RF is a bit more subtle than that, and I'm not convinced that Scott
Aaronson has really "debunked" it.

"But clearly, even if no one literally measures Charlie in the {|0〉,|1〉}
basis, _he’s still there, thinking either the thought corresponding to |0〉 or
the thought corresponding to |1._ And likewise Diane. Just as much as Alice
and Bob, Charlie and Diane both exist even if no one measures them, and they
can reason about what they know and what they know that others know. So then
we’re free to chain together the “certainties” of Alice, Bob, Charlie, and
Diane in order to produce our contradiction."

You can't use this argument without also explaining what "thinking" means -
because in fact it makes no sense unless you _assume consciousness exists as a
quantum state which allows a phenomenon called "thinking."_

And philosophically and practically, that's a very, very large can of wormns.

So this ends up in the usual place: it's not obvious how using an idea no one
understands - like consciousness - to explain another idea no one understands
- like QM - is supposed to solve any of these problems.

~~~
Strilanc
In order to implement the measurement described in the thought experiment, you
basically have to uncompute Charlie's state back to the start of the
experiment (to disentangle him from the qubit you want to measure), do the
measurement on the single qubit, then recompute Charlie forward. This means
that when Charlie is making deductions about the current state of affairs,
like "if my qubit is |0> then the other qubit is |+>, that thinking needs to
be valid during the computation _and during the recomputation_. But the
conclusions Charlie is making are not correct during the recomputation, e.g.
it is no longer the case that if his qubit is |0> then the other qubit is |+>
at that time, and as a result the whole argument (based on Charlie's reasoning
being valid so that an outside agent can use his conclusions) falls apart.

More details:
[https://algassert.com/post/1904](https://algassert.com/post/1904)

------
rbanffy
I find the concept of consciousness applied here a bit disturbing. Shouldn't
we treat the observation as information leaving the observed system and
propagating causal effects to other systems? A data recorder is not conscious,
but notes information that passes through it and, therefore, observes a single
state instead of a superposition.

~~~
elektropionir
Consciousness comes indirectly into quantum mechanics through the measurement
postulate. You have to assume something special about measurement which breaks
unitarity. Not all physicist are convinced, but it is the traditional way
quantum mechanics is taught (all of the "transition probabilities" are really
measurement probabilities). The problem is that you can't tell if your
apparatus caused the collapse or if it was you that measured the apparatus
that then caused the collapse. And because you can only know that something
was "observed" when a conscious physicist makes that final readout you end up
with a solipsistic situation where the only thing you can be certain of is
that it was that last conscious observer that could have for sure collapsed
the wave function. It could be that the collapse happened in the apparatus
itself but as far as I know you have no way of telling the difference between
it projecting the wave function of the measured system or you projecting the
wave function of the apparatus into a pointer state. Basically consciousness
sneaks in through the fact that there is no definition of what constitutes a
measurement - what makes one physical process a measurement as opposed to all
others that are unitary and the only thing you are certain of is that final
"conscious" readout should count as measurement.

~~~
brummm
This is misleading at best. A measurement has nothing to do with a conscious
observer taking the measurement. An automated experiment that could note down
the result of an experiment would note down the result without any conscious
observer having to check in and the result would be the exact same.

~~~
akvadrako
No, he is basically correct. Traditional QM requires an observer who is
outside the system being measured to cause non-unitary evolution.

You can always consider your automated apparatus to be part of the system and
hence governed by unitary evolution.

~~~
millstone
Traditional QM requires an outside observer but has nothing to do with
consciousness. Consider the collision events recorded at the LHC: the vast
majority have never been looked at by a human.

~~~
akvadrako
They have not been explicitly looked at, but they have been observed in the QM
sense. That’s because decoherence has spread those records to conscious
observers.

If the results had been kept completely isolated from all people, you could
still say a measurement hasn’t occurred.

~~~
millstone
That's just not what traditional QM says. Traditional QM separates quantum
systems (microscopic) from measurements devices (macroscopic). A measurement
occurs when the measurement device interacts with the quantum system. You do
QM by predicting the results of these measurements. Consciousness does not
enter into it.

~~~
BadThink6655321
Until you get information from the measurement, it didn’t happen.

~~~
rbanffy
Can it be considered as until it causally affects something else (the
observer), its state is not defined? Isn't it a causal relation that collapses
the superposition?

------
boxed
I read and skimmed and read and I gave up finding the substance. Can someone
summarize?

~~~
refulgentis
honestly, i felt the same way after a good 15-20 minute read - I think it's
one of those where you have to read it a few times, leave space in between,
and Google as soon as you start getting confused

~~~
boxed
There's too much filler background too...

------
toxicFork
It's silly to take Schrödinger's Cat literally.

It's a convenience to explain states within equations. When you say "the cat
is both alive and dead at the same time", you're simply saying "in this
equation, do not assume that this variable will be one or zero, calculate the
results for both conditions", and the final outcome will possibly be one of
these calculated results.

The more such variables you have, the more different results you may get.

------
rdiddly
"Does the cat experience superposition?" Questions like these have always
seemed to me like mistaking the map for the terrain. Quantum mechanics is a
model, an abstraction of reality, trying to cope with uncertainties in reality
that our observation & measurement technologies can't really settle. It's
interesting but not to be taken quite so literally. Right? I dunno, clearly
I'm not a physics expert. But I'm not a music expert either (actually I am but
let's pretend), but I know that the sounds that please or impress advanced
academic peers/mentors/funders rarely overlap with those that please the rest
of the world. The Art and Architecture departments are like that also, and I
suspect but can't prove that e.g. Economics, and more to the point, Physics,
are too. I probably sound like I'm verging dangerously close to anti-
intellectualism here, which I don't really want to do in the current cultural
climate, but if anything it's the opposite: We should remember that believing
someone implicitly just because they're an intellectual is also anti-
intellectual. It's an appeal to authority which is one of the classic logical
fallacies. Someone is not necessarily immune to institutional pressures (nor
are they even necessarily an honest person) just because they're an
intellectual. But you need to conduct your own research or at least a survey
of the existing research before you can call yourself even a legitimate
skeptic (as opposed to just a troll)! Which is why I'm stopping short of
actually saying anything... so hey, my apologies for the time-wastage!

------
peter_d_sherman
>"Because the two photons appear to communicate _faster than the speed of
light_ — something prohibited by his theories of relativity—this phenomenon
deeply troubled Albert Einstein, who dubbed it “spooky action at a distance.”

These concerns remained theoretical until the 1960s, when physicist John Bell
devised a way to test if reality is truly spooky—or if there could be a more
mundane explanation behind the correlations between entangled partners."

[...]

Such “Bell tests” have since been carried out, with a series of watertight
versions performed in 2015, and they have _confirmed_ reality’s spookiness."

Logic:

If you believe that the Bell Test is correct -- you must equal-and-oppositely
believe that the speed of light is NOT the upper limit of speed in the
universe, that is, that Faster-Than-Light (FTL) speeds are possible.

Conversely, if you believe that speed maxes out with the speed of light, and
that nothing can travel faster than the speed of light -- then you equal-and-
oppositely believe that the Bell Test is wrong.

But, you cannot believe that nothing can travel faster than the speed of light
AND that the Bell Test is correct, simultaneously -- as this would result in a
logical paradox...

(Choose one, _but not both at the same time_...)

~~~
AnotherGoodName
The trick is to talk in terms of communicating information faster than the
speed of light. Both relativity and quantum theories agree that there's no
communication of information faster than the speed of light. Two wave-
functions collapsing to opposite states lightyears away doesn't actually allow
two people to communicate in an FTL way.

~~~
Lichtso
Exactly, so it becomes a question of the very inner working of the universe
itself: How does the universe spontaneously assign the states consistently
without communicating and also without assigning the states beforehand.

This is precisely why the experiment was proposed, to show this conflict in
our understanding of the constraints.

~~~
3pt14159
If one bends a piece of paper such that two faces nearly meet then pokes a pin
through the page and makes two holes in the page essentially simultaneously
from the perspective of the two dimensional beings on the page it appears that
the two events happened far apart and that "something must be moving
information at faster than the speed of light" when the reality is more
complex.

That's how I mentally think about entanglement. I doesn't need to operate
through the universe as I understand (or operate within) it.

------
bookofjoe
[https://archive.vn/ycC6W](https://archive.vn/ycC6W)

------
Gravityloss
The Schrödinger's cat paradox is a joke. Basically every time it's posted in
some popular science article, it's a waste of time.

The superposition collapses way before the cat is affected, when more than a
handful of atoms is concerned, way before the hammer even moves.

------
jungletime
I have a pretty basic understanding of this. I think of QM measurement, like
trying to find the highest wave in the ocean.

At at any moment, there might be some n number of waves that are the highest.
But not until the exact moment you measure the answer exists.

------
cloudking
In Schrodinger's Cat Paradox isn't the cat itself an observer? It has eyes,
therefore it would observe the poison and be dead.

~~~
wongarsu
If the cat is an observer, then is the bottle of poison also an observer? Are
the cells of the cat? Are the atoms of those cells? What is it that gives the
cat observer status?

The intent of the thought experiment was to show that the Kopenhagen
Interpretation of quantum physics is ridiculous. In the many-worlds
interpretation for example there is no paradox, as time goes on more and more
worlds exist where the cat died at some point.

~~~
cloudking
Going off the double slit experiment, it seems the definition of an observer
is something that can take in light, interpret and measure it. The examples
given are eyes and cameras. (I'm not claiming I understand this, just trying
to)

~~~
Green_man
"observation" isn't important, it's enough interaction to decohere the
superposition, or in another sense, entangle it with the environment. A
polarization filter could be considered an "observer" in some sense, but I
think focusing on observation results in a less clear and truthful
understanding of what a measurement is. A polarization filter rather interacts
with the light in a strong enough way to force conditional behavior based on
its polarization. This results in photos that have a superposition of
different polarizations to probabilistically become one of the polarizations,
wrt the respective amplitudes of each polarization for that photon.

------
lostmsu
> “The paper is an important philosophical study,”

If that line would be in the beginning, I would not have bothered to read the
article :/

