
Physicists found a new quantum paradox that casts doubt on a pillar of reality - walterbell
https://www.sciencealert.com/a-new-quantum-paradox-throws-the-foundations-of-observed-reality-into-question
======
bondarchuk
The original Wigner's friend paradox:
[https://en.wikipedia.org/wiki/Wigner%27s_friend](https://en.wikipedia.org/wiki/Wigner%27s_friend)

The paradox seems to rest on magical thinking about consciousness, and if one
simply accepts that a conscious observer can be in a superposition like any
other piece of matter, the paradox is resolved.

And, from the article:

 _For Wigner, this was an absurd conclusion. Instead, he believed that once
the consciousness of an observer becomes involved, the entanglement would
“collapse” to make the friend’s observation definite.

But what if Wigner was wrong?_

Well, obviously Wigner is wrong, sorry for being flippant.

In this paper (preprint here:
[https://arxiv.org/pdf/1907.05607.pdf](https://arxiv.org/pdf/1907.05607.pdf)),
the magical thinking about consciousness seems to be transmuted into _"
“Absoluteness of Observed Events” (i.e. that every observed event exists
absolutely, not relatively)"_. The authors (it appears to me) mean by this
that if an observer performs an experiment, while this observer is himself in
a superposition, we have to regard the outcome of the experiment as absolute
(i.e. not in a superposition) because it was made by a (conscious) observer.

In my opinion, both " _Absoluteness of Observed Events_ ", and the equivalent
from the layman's article, " _When someone observes an event happening, it
really happened_ ", is a disingenuous and confusing way of talking about
observers who are in a superposition. We have crossed over from "quantum
mechanics is weird" to "these superficially intuitive but clearly false
assumptions about quantum mechanics are weird".

(by the way, I read the article here: [https://theconversation.com/a-new-
quantum-paradox-throws-the...](https://theconversation.com/a-new-quantum-
paradox-throws-the-foundations-of-observed-reality-into-question-144426)
because that site doesn't think I'm a robot and then redirects me to the
homepage after filling out the captcha)

~~~
canjobear
> if one simply accepts that a conscious observer can be in a superposition
> like any other piece of matter, the paradox is resolved.

It’s not so simple. Suppose you’re in a box and observe a quantum experiment,
and then I open the box and observe you. Then before I open the box you’re in
a superposed state |x> \+ |y>, corresponding to the two possible outcomes x
and y. Fine, no problem so far. But what is your own subjective experience?
You, subjectively, inside the box, will only ever observe yourself to be in
|x> or |y>, never |x> \+ |y>. Even if from the outside your brain can be said
to be in a superposed state, your experience of the world is not superposed.

~~~
ahelwer
Many-worlds interpretation takes care of this. Anyway, how do you know your
experience of the world cannot be superposed? Have you ever been in
superposition? We make up stories to maintain consistent histories all the
time.

~~~
canjobear
> how do you know your experience of the world cannot be superposed?

For your experience of the world to be superposed it would mean that you carry
out a quantum experiment with two mutually exclusive outcomes |x> and |y> and
you actually experience the superposed result |x>+|y>. This would be like
opening the box in the Schroedinger's cat experiment and actually observing
the cat to be |alive>+|dead>, instead of either alive or dead. Maybe it's
possible, but such an experience has never been reported.

~~~
jfengel
It's "possible", but not really possible. The larger the object is, the harder
it is to maintain superposition. Even the slightest nudge will tend to push it
all into one state or other. Seeing the superposition directly would be like
standing twenty octillion strands of spaghetti on end.

So it's "possible" but would never happen in a trillion lifetimes of the
universe. You can tell the difference between that and "impossible" by
watching the quantum mechanics work for a few isolated particles, and
observing what it means for them to fall out of superposition equilibrium. But
in practical terms, it's equivalent to impossible.

------
Zenbit_UX
Whenever I hear about weird shit from the realm of quantum physics (this
theory, double-slit, etc..) I can't help but think:

Why would I hardcode values for imperceptible objects, that would take an
enormous about of ram and cpu time to constantly update values in the off
chance it's needed.

Much more efficient to optimize for what the _player_ can see at their
perspective. Oh and I should probably code in some error handling in the fluke
event one of these particles is detected, I'll just calculate their position
retroactively, the user will never be able to tell and we can host way more
players due to the reduced memory.

It would seem to me that god is a junior dev and no one reviewed his pull
requests.

~~~
sgillen
One problem with this view is that “unobserved” particles still take up a
large (possibly larger?) amount of computation. Rather than being in one
position, it acts like a wave, being a little bit in every possible allowable
position. These probability waves also interact with each other (which is what
the double slit experiment demonstrates).

That being said if it was demonstrated that un collapsed wave functions are
somehow more efficient to calculate that would definitely give credence to the
simulation hypothesis.

~~~
Zenbit_UX
> That being said if it was demonstrated that un collapsed wave functions are
> somehow more efficient to calculate that would definitely give credence to
> the simulation hypothesis.

Well said. I can certainly imagine a few functions that may prove to be more
efficient at generating waves than fixed known positions + velocity for every
subatomic particle in the universe.

Here's the part that really takes us off the rails, if we assume for a minute
that we are in a simulation and that the parent world has godlike resources
compared to our own and they likely have similar hardware concepts (ram, cpu,
gpus, maybe even ASICS) then what functions are more efficient would depend on
which hardware they have less of.

If ram is plentiful why not have fixed known values for every particle? Store
it in memory and let the gpu detect collisions.

If gpus are plentiful (my guess) and we're bound by ram limitations, best to
only store positions of things that are visible and clear the rest out of ram
for more important calculations.

Imagine how inefficient it would be to render and simulate black holes
colliding on the other side of the universe if the players will never even
notice. Just queue up the function and run it on off-peak hours. Save the
extra server resources for other simulations running in parallel.

If I'm right - a big if - we're likely an anomaly or early prototype among the
simulations, one in which the dev team never imagined a race would evolve and
progress enough to measure the bounds of their container. If I'm right again
on this last point, we're likely being monitored closely to decide if
subsequent patches require more resources to simulate completely and avoid
player's realizing they're in a simulation or accept it as a remote
possibility and move on.

~~~
dencodev
if we're a simulation i somewhat doubt whoever made our simulation is really
worried about "resources" and "efficiency". Whatever real universe that may
exist may not even follow our laws of physics. Maybe energy is actually
unlimited and free in the "real world". Maybe matter can be made from nothing
effortlessly.

~~~
thu2111
Why would someone build a simulation of a world utterly unlike their own?

When we build simulations for ourselves, they're always attempting to
approximate reality as closely as possible. The goal is to learn useful things
about our own world or society and to try out many forking paths, in a
simplified representation of reality.

If we're in a simulation it stands to reason that whoever is running it is
somewhat human-like, and exists in a world that has basically the same
physical laws ... or at least, similar enough that sociological and
technological development would be the same. For instance, the speed of light
barrier is pretty damn inconvenient for us but would be great at blocking an
arbitrarily large population and state space explosion. And why are these
magic physical constants so arbitrary anyway?

If we _are_ in a simulation, and our simulators _did_ want to limit their
resource consumption, adding in a few physical laws that are never really a
problem in daily life and which block us from colonising the galaxy would be a
nice way to do it.

~~~
dencodev
Conversely, I would wonder why anyone would simulate something so similar to
their own reality. We've already seen with humans that history repeats itself
endlessly. Humans haven't really fundamentally changed in thousands of years.
And humans do studies of the sociology of other species all the time. I think
it'd be much more entertaining to simulate a world the laws are near opposite
of our own. I would want to see what a species is capable of when restraints
are lifted. To limit them to a single planet seems boring.

As an aside, I think one of my personal arguments that we're in a simulation
is that we live in such an interesting time. We're beyond a world with 95%
farmers. Technology is advancing faster than ever before. It's such a critical
time in human history and the 20th century is personally where I'd choose to
start a human simulation. It's convenient that this is our shared spot in
time.

------
Strilanc
The article lists three assumptions that one might intuitively think hold. The
problematic assumption is this one:

> When someone observes an event happening, it _really_ happened.

Given the experiment from the paper, I would rephrase this assumption as "it's
not possible to rewind things". But obviously inside a computer simulation
made up of operations that are all individually reversible, it's trivial to
rewind things.

The experiment sets up a situation where certain information is reversibly
recorded, and then the records are unmade by temporarily rewinding. The
rewinding is obfuscated by hiding it inside of a measurement that is
incompatible with the presence or absence of the record. I guess the authors
might disagree about the measurement implying rewinding, but as a bit of
evidence I'll note that Scott Aaronson and Yosi Atia have shown that
performing the measurement in question over a simulated agent is at least as
expensive as rewinding the simulated agent [1]. Whatever is being done, it is
doing some _seriously expensive_ screwing around with the agent's state. It's
like the experiment has a step where you feed the human through a giant meat
processing plant, and for some reason everyone is pretending that's not
somehow important.

Basically, the authors are appealing to the intuition that humans are big
complicated in-practice-irreversible things, so clearly a record is permanent
if it has affected the state of a human. But then they imagine instantiating
the human's state inside a ridiculously powerful computer capable of
reversibly simulating time advancing and of performing operations that have
been engineered specifically to mess with the presence or absence of the
record's effects on the human's state. Surprise surprise, the record gets
messed with. Then for the actual experiment the big complicated ball of
dependent spaghetti that is a human is replaced by a nice simple photon going
along one path or another path.

1:
[https://www.scottaaronson.com/blog/?p=4786](https://www.scottaaronson.com/blog/?p=4786)

------
colordrops
Based on my very limited understanding it seems that anything that interacts
with a system can be treated as an "observer", and thus a chain of
observations can occur as one particle interacts with the next, enlarging the
system that is in superposition for the next observer.

Do physicists axiomatically treat a "conscious observer" as an atomic unit? It
seems the case based on neurological and psychological research that the mind
is actually not a single unit but many units working together, and the sense
of a singular self is an illusion, which would correlate with the fact that we
are made up of a conglomeration of atoms and systems made of these atoms.

When we say that a person is observing a quantum system, could this actually
be a cascade of observations of various parts of the mind rather than a
singular event, since the mind is not monolithic?

On a side note (and perhaps unrelated), if different parts of the brain/mind
could be in different quantum states, could this be a factor in how the mind
operates?

------
jonahbenton
I don't know to what degree the metaphor is accurate but as a non-physicist I
find thinking about quantum mechanical experiments easier if I think of them
as running code on a vast decentralized computing infrastructure.

The concept of "measurement" is just executing code on one node that populates
local registers- "creating" not "measuring". Yes- by running code you are
pulling on a reality fabric that we still know almost nothing about. But I
find it easier to visualize than relying on my colloquial/non-QM intuition in
words like "measuring"\- which implies something like a single centralized
reality database, not a creative decentralized infrastructure. QM experiments
seem to create things, not measure them.

Would love to learn metaphors of folks in the space.

~~~
thechao
I’m just now teaching myself QM (20 years after school). I can tell you that
in QM, seemingly innocuous phrases like “locality” have highly unintuitive,
nonstandard meanings. I’m just now getting a glimpse at how amazingly fucking
_awful_ pop-sci QM articles are.

If you’re interested in QM, read “The Theoretical Minimum”; the second book
gets into QM. There are video lectures of the same material that complement
the series, we’ll.

~~~
jonahbenton
Appreciate the reference, cheers.

~~~
guerrilla
There are lectures by Susskind at Stanford on YouTube that go with them by the
way.

------
henearkr
The part that seems the most dubious to me is the "choice":

> 2\. It is possible to make free choices, or at least, statistically random
> choices.

I don't see what would be really compelling in that.

If it's false it would just mean that our actions are all kind of
mechanistically decided by other events, and that does not shock me.

Other point:

> 1\. When someone observes an event happening, it really happened.

What if it really happened in the reality of the observer (and maybe not in
other realities)? What is meant by "reality"? Some insight is to be gained by
precising what we call the reality, in relation to the corpus of all the
observations in what we believe is our universe.

~~~
coliveira
The main problem of quantum interpretation is the supposed, artificial,
distinction between observer and observed system. In a quantum world this
distinction is not possible, every event capable of "observing" a system is
itself part of the system, modifying it. That's why such interpretations
(postulating this separation) give all kinds of strange paradoxes that are
impossible to solve. In the quantum world, there is no such thing as an
observer, it is just all part of the system.

Consider for example the system composed of a pool table. In classical physics
we can assume we can always measure the position and momentum of all balls in
the table. But what would happen if measurement was not possible without big
changes in position and velocity? Suddenly the whole notion of "observation"
would lose its meaning, and the only way to describe the pool table is as a
probabilistic mesh of balls moving around in uncertain directions.

~~~
henearkr
Yes, I think you put your finger on it. As the observer is part of the system,
his "reality" is as much superposed, entangled, etc., as the quantum events
that compose it (himself and his observation too).

That would give credit to the multiverse interpretation of quantum mechanics
then.

Maybe the observation process of a quantum phenomenon by a human observer is
akin to the orthogonalization of a matrix:

as the observer becomes entangled with the observed particle, each possible
observer-eigenstate (i.e. any observer in "his reality") ends up observing an
eigenstate of the observed quantum phenomenon, instead of a dirty
superposition.

To call it "orthogonalization of the observer-observed system" would be more
descriptive than "wave-collapse", but the main difference is that the
orthogonalization treats in parallel all possible outcomes, each linked to a
different state (outcome) of the observer too, whereas the "collapse" view
insists on the fact that the observed eigenstate is unique. And moreover, at
least in mathematics, there are conditions for the orthogonalization to be
possible at all, so that should be interesting.

------
4ad
Actual paper:
[https://arxiv.org/abs/1907.05607](https://arxiv.org/abs/1907.05607)

~~~
mellosouls
Rendered for web:

[https://www.arxiv-vanity.com/papers/1907.05607/](https://www.arxiv-
vanity.com/papers/1907.05607/)

------
menzoic
Veritasium has a great video that explains the concept of parallel worlds vs
wave collapse in a single world
[https://youtu.be/kTXTPe3wahc](https://youtu.be/kTXTPe3wahc)

~~~
amelius
Nice video. Now I wonder if God uses structurally shared data structures in
his implementation of the world. I also wonder if there can be a kind of
continuous description of branching that is more amenable to calculus than the
discrete tree-like branching.

~~~
c1ccccc1
I think MWI actually predicts continuous branching. The prescription for MWI
is just to run the Schrodinger equation forwards in time. So the branching
would look like one blob of probability gradually becoming bimodal, and then
splitting into two components with less and less overlap. (There might also be
3-or-more-way branches, not just binary splits.)

~~~
elwell
Tell me about the 'superworld' that hosts the many worlds.

~~~
c1ccccc1
I mean, physicists don't usually go around talking about superworlds, but
maybe this corresponds to the concept you want?:
[https://en.wikipedia.org/wiki/Hilbert_space](https://en.wikipedia.org/wiki/Hilbert_space)

------
lisper
> if the "friend" is a human-level artificial intelligence running in a
> massive quantum computer.

Well, there's your problem right there. No AI can run on a quantum computer.
Intelligence is inherently a classical phenomenon because it requires copying
information, and quantum states cannot be copied, only classical states can be
copied.

The classical world "emerges" from the quantum world when you take a quantum
system and choose to consider only a subset of its degrees of freedom. When
you do that, what results is a "mixed state" which behaves classically. This
is not a reflection of any (meta)physical reality, it's just a consequence of
your point of view. But here's the thing: you yourself are a subset of a
quantum system, and so you yourself have no choice but to take this point of
view. You cannot ever take the "god's-eye view" and "see" the whole system.
That is fundamentally impossible because "seeing" requires copying
information, quantum states can't be copied yada yada yada. Even God cannot
"see" the god's eye view!

~~~
Zenst
> quantum states cannot be copied

Wouldn't quantum entanglement enable a comparable ability?

~~~
gjhan
Entanglement means that there are systems with highly (more-than-classically)
correlated state - that the combined state is something that can’t be
represented by considering the systems independently - not that the states are
the same. The no-cloning theorem prohibits a _process_ that takes the state of
a system and replicates it on another system. It’s certainly possible to have
or to generate entangled sets of systems that have identical separable state,
but not to copy an arbitrary state.

------
gliese1337
I'm pretty sure "many-worlds is false" is _not_ , in fact, a "pillar of
reality".

------
08-15
> Take a look at these three statements [...] they cannot all be true

Okay, so we have to kill one. The easiest one to kill is

> It is possible to make free choices.

In other words, quantum mechanics is incompatible with free will. This is
clearly shocking to any physicist who believes in Free Will (as defined by
philosophers thousands of years ago). But hasn't Free Will been recognized as
nonsense for at least two centuries by now?

~~~
katmannthree
> But hasn't Free Will been recognized as nonsense for at least two centuries
> by now?

Among some, sure and it's not just physicists [1].

Acknowledging that the concept we've called free will is not likely to be real
has some troubling implications regarding how we've structured our society
which is likely one of the reasons it's not talked about very often.

[1]:
[https://www.youtube.com/watch?v=ihhVe8dKNSA](https://www.youtube.com/watch?v=ihhVe8dKNSA)

~~~
elwell
The members of a system can 'experience' free will from their perspective, but
it's a still a deterministic line of causation; their free will is part of the
determinism.

------
stared
Have it ever happened o you that you read "a pillar of reality" and it turned
out to be more than a clickbait?

Me neither.

(To make it clear: the content is interesting, even if clearly for popular
science audience (some statements about physics are false, e.g. "These are all
intuitive ideas, and widely believed even by physicists." The title is worth a
tabloid.)

~~~
booleandilemma
I'm still trying to figure out what exactly the discovery is, if there's any.

------
rantwasp
this is not convincing at all. we pretend that we can have perfectly isolated
quantum systems (a particle, a few particles) and we can reason about and
extrapolate the findings. we cannot have isolated particles - they can be
regarded as isolated for experimental purposes but the reality is that
probably the whole universe is a massive wave function that encompasses
everything and we can approximate in some really special cases (ie system
above).

we also pretend that consciousness is something special and altering the state
a somewhat complicated wetware had consequences on “reality”. it doesn’t.

the measurement problem is an extremely good example of how we think. a
measurement does not make sense to a cow. it’s abstract. we made it up. we
have conventions that help make it useful, but those conventions break down
when our senses (or things we use to amplify out senses) cannot measure what
we want to measure.

------
hggfkkbcfd
One this I always notice to be missing from discussions of quantum physics is
the effect of scale. Does differences scale have relativistic effects, in a
similar manner to differences in internal frames, and if at what do events in
one scale frame of reference become simultaneous of an observer in another?

Note: IANAP

------
zxcvbn4038
So, Schrödinger's cat has been alive the whole time and it’s rest of us in a
state of superposition because the cat is conscious but can’t observe anything
outside the box? Or because we are conscious and the cat conscious, we all
retain our states regardless if we are in or out of the box?

------
BTCOG
Think of it as LOD generation in a game. As something observes or is near
enough to observe, atomic matter is generated on demand. The Matrix; our
simulation.

------
thayne
How is this a new paradox? Isn't this paradox the whole reason for different
interpretations of Quantum Mechanics?

------
mensetmanusman
Maybe our dream state is how we resolve and wipe quantum paradoxes from our
days experience.

