
Superdeterminism: The path we didn’t take - chmaynard
http://backreaction.blogspot.com/2019/12/the-path-we-didnt-take.html
======
dchichkov
A nice and compelling argument in that paper: _" The classical Liouville
equation is linear in the probability density due to conservation of
probability. But this linearity says nothing whatsoever about whether the
dynamics of the underlying system from which the probability density derives
is also linear. Hence, for example, chaotic dynamical systems, despite their
nonlinear dynamics, obey the same linear equation for probability density. To
us, this close formal similarity between the two equations strongly suggests
that quantum physics, too, is only the linear probabilistic description of an
underlying nonlinear deterministic system."_

But, similarities in equations surely can be misleading ;)

~~~
tomxor
> linear probabilistic description of an underlying nonlinear deterministic
> system.

The math is way over my head, but this sub-statement resonates with me deeply
and has been my crude but overarching view of the physical world and our
interpretations of it for a long time - except applied more broadly - as a
description of the interaction between multiple layers of abstractions of
reality (whether the _things_ behind those designated abstractions are natural
or human made, e.g transistors for digital logic, a "deterministic" quantized
layer created atop a non-deterministic one).

It is layered because each deterministic one is only _effectively_
deterministic by being predictable " _enough_ " in a highly uniform way. The
next layer then often becomes viewed from a probabilistic perspective again
due to chaotic interactions of the previous one (often computationally
irreducible). The lack of access to massive initial state and in-feasibility
to compute prediction based on the underlying mechanisms are the only reason
we switch back to the probabilistic view at these non-fundamental levels of
abstraction.

Now I understand quantum physics is not supposed to be such a layer, because
we didn't start out with an existing working concept of what's underneath it
in the way we know whats underneath equations for some statistical mechanics
for example - but from the perspective of a complete amateur the idea of
superdeterminism seems quite natural! - yet at the same time I can't help
wonder if there is yet another probabilistic layer underneath :)

------
themgt
I find this Quora answer convincingly reflects my thinking as to why
Superdeterminism can't possibly be correct given Bell’s theorem[1]

Skimming the actual paper[2] I'm not really seeing a convincing explanation,
this in particular just strikes me as hard to believe / failing Occam's razor:

 _The belief that such tests tell us something about (the implausibility of)
Superdeterminism goes back, once again, to the idea that a state which is
intuitively “close” to the one realized in nature (eg, the wavelength of the
light from the distant quasar was a little different, all else equal) is
allowed by the laws of nature and likely to happen. However, in a
superdeterministic theory what seems intuitively like a small change will
generically result in an extremely unlikely state; that’s the whole point. For
example, in a superdeterministic theory, a physically possible counterfactual
state in which the wave-length of the photon was slightly different may also
require changes elsewhere on the past hypersurface, thereby resulting in the
experimenter’s decision to not use the quasar’s light to begin with._

"Reality is a giant deterministic conspiracy" is more plausible than
abandoning local realism? They do (kinda?) propose an experiment at least?

[1] [https://www.quora.com/Why-do-some-crackpot-scientists-go-
aft...](https://www.quora.com/Why-do-some-crackpot-scientists-go-after-super-
deterministic-theories-when-Bells-theorem-has-proved-that-local-realism-is-
false) [2]
[https://arxiv.org/pdf/1912.06462.pdf](https://arxiv.org/pdf/1912.06462.pdf)

~~~
perl4ever
I'm not sure if everything being deterministic is an abhorrent, invalid
option, but I also don't see why reality has to be local. I mean, the
limitation of light speed is something that exists to make a consistent
theory, not something that somehow has value in itself...?

My problem is probably not just a lack of math, but a lack of taste.

~~~
tsimionescu
> I mean, the limitation of light speed is something that exists to make a
> consistent theory, not something that somehow has value in itself...?

The limitation of causation to a constant speed is well proven in experiments,
and seems to be a fundamental aspect of the universe at large scales. If this
same limitation doesn't hold at small scales then either:

1\. There must be some cutoff between large scale and small scale, and small
scale events can't influence large scale events. 2\. Instantaneous action at a
distance exists at large scales as well, and so our theories are wrong (we
need a new theory to explain the observations of the speed of light etc.).

This is all not to mention that we have not noticed any particle moving past
the speed of light, and that we have measured the same constant speed of light
at quantum levels as well (a photon measured from a moving detector has the
same speed as one measured from a static detector).

So that way lies nothing good. On the other hand, rejecting local realism
doesn't mean that QM rejects the speed of light being constant - quantum
entanglement can't carry information, so it can't produce actions at a
distance.

Also, note that the most common interpretation of QM is neither local nor
'real' \- that is, it implies both that particles have no definite state until
they are measured, and that QE propagates at infinitite speed. That is, when
you fire two entangled photons, neither of the photons has any value for
polarization until they are measured; however, when one is measured, it
acquires a particular spin, and the other one also acquires the corresponding
spin instantaneously, possibly on the other side of the galaxy.

Now, one problem with all this is that it is extremely non-intuitive, and does
not apply to the large-scale world (an apple is red whether I look at it or
not). Related to the second issue, there is the problem of measurement: in a
theory which rejects realism, the act of measurement has a fundamental
physical effect, but there is no explanation for this mechanism, it is simply
postulated. Note that a photon interacting with another photon is not
measurment, they will each retain a superposition of states until a
measurement happens.

~~~
YeGoblynQueenne
Thanks for the explanation. It really is non-intuitive and hard to get
especially just from informal texts.

What I don't get at all is the bit about quantum entanglement not carrying any
information. Apparently, that has to do something with the fact that the
collapse of the wave function is a random process? But, if you have
probability then you have information, yes? What's the explanation?

~~~
tsimionescu
I don't know the full maths behind it, but the most important aspect is that
you can only perform one measurement on the superposition state - after your
first measurement, the particle acquires a definite state, and any subsequent
measurements are guaranteed to show that same state. If you are the first one
to measure the state of any of the pair of entangled particles, your
measurement will cause both particles to take on a definite state.

But even if you are the second one to do the measurement, and the particle has
already acquired the definite state because of the other measurement, you
can't tell that your measurement result was already guaranteed, since you
can't perform another one on the same state to compute the distribution.

~~~
YeGoblynQueenne
Thanks.

------
knzhou
I've always been mystified at why people take superdeterminism as a good
explanation for anything, when it actually acts as a stopsign for thought.

For example, suppose I am betting with you on the outcomes of a coin toss. You
call heads, the coin comes up tails, you give me some money. You call tails,
the coin comes up heads, you give me some more money. This repeats a number of
times.

The common sense response is to start suspecting that I am rigging the game,
i.e. that the simple model of the coin flips being independent and random is
wrong. The superdeterminist response is to say, "no, your guesses have been
superdetermined to be all wrong by the initial conditions of the universe --
keep on playing!"

You can use superdeterminism to explain literally anything (not merely a lot,
but actually, _literally_ everything) while gaining precisely zero insight
into what is actually going on, and precluding any future insight. Sure, it
fixes a few philosophical problems, but so does saying you're a brain in a
vat; in both cases you throw out all of science as a side effect. While their
paper does address some philosophical objections, it doesn't even mention this
scientific objection, which seems far more severe to me.

~~~
ReadEvalPost
I don't really understand what your coin flip metaphor is supposed to mean in
the context of the paper. That Superdeterminism could be used in an entirely
facile way doesn't really suggest anything about the theory itself.

When choosing Superdeterminism as an ontology it suggests different paths for
doing research, paths that are unexplored and potentially full of insight.
That's what is exciting about it to me.

~~~
rtpg
Superdeterminism boils down to "the universe has baked in all results for all
these quantum interactions"

In a dumb "the universe in a computer" metaphor, it's saying that instead of
having `do_quantum_thing` be a function taking various physically interesting
parameters and then resolving to something interesting (and thus making QM be
_about finding that_), we just have a huge array like
`result_of_all_quantum_things_ever_to_exist` filled with random garbage.

It's a theory that precludes any notion of predictivity in effects. It's
nihilism for physicists.

~~~
trevyn
I think this is a misinterpretation — superdeterminism says that there is no
true randomness in the function, not that the function is of any other
particular form. The excitement is from the possibility that the function may
be very simple (in Kolmogorov complexity terms), yet yield only one possible
result for the state of the universe at each point in time. (Much like the
process for calculating pi is simple and there is only one value for pi, but
without knowing the process, there appears to be a lot of complexity or
randomness.)

------
gliese1337
I find it strange that they claim that QM lacks any explanation for
measurement.

There _are_ explanations for measurement. Not everyone agrees with any single
one of them, but they definitely exist. Superdeterminism is one, but it's not
the only one. It is really only the _Copenhagen Interpretation_ of QM that has
a measurement problem.

Personally, I am on board with the "measurement is just entanglement" solution
(it seems intuitively obvious to me, but then I'm sure superdeterminism seems
intuitively obvious to those who believe in it as well), which makes
superdeterminism unnecessary.

~~~
repsilat
I'm also a Many-Worldser, but I don't quite know how to answer the question
"How does the Born Rule work?"

That is, if "worlds" branch off with some amplitudes, and there's a "me" on
this branch and another on that branch, how does it make sense to talk about
the probability of "me me" being this one or that one?

Empirically we know how to calculate it from the amplitude, but why is that
more reasonable than any other answer (if any answer is reasonable)?

~~~
gliese1337
Well, yeah, there is that... I suppose one could argue that lacking an
a-priori explanation for the way probability is allocated over state-space is
equivalent to lacking an explanation for measurement, but that seems to me
like claiming that we have no answer to how thermal emission of light works
because we can't explain the measurement rule in QM, which I expect most
physicists would balk at.

Yea, there is still work to be done at a lower level, _and_ there are other
competing explanations at this level, but that doesn't mean that we don't have
an explanation at this level. "How does the Born Rule work?" is a lower-level
question than "how does measurement work?"

~~~
repsilat
The "measurement problem" is really a Copenhagen-specific thing --
"measurement" is the fundamental and identifying mechanism of the
interpretation, and it's problematic. And In the Copenhagen interpretation the
Born Rule is inextricably tied to measurement outcomes.

I guess you could say that MWI removes the wishy-nastiness around what
constitutes measurement, when it happens etc, and that could constitute
"solving the problem", but I think

\- Some of "the problem" has just been moved outside those borders. (And fine
-- the MWI doesn't need to solve _every problem to be an improvement. And I do
think it 's an improvement.)

\- The Born Rule is _weirder* in the MWI. In Copenhagen it's axiomatic: We
explicitly roll the dice, a nondeterministic outcome happens, that's the
mechanism. In MWI it's an afterthought: The wavefunction evolves
deterministically, and oh-by-the-way you should weight the likelihood of
finding yourself here or there by the squared amplitude.

Maybe that's unfair though?

------
zyxzevn
Since we are looking at an alternative interpretation:

Max Planck's Loader Model - the simplest interpretation that is never looked
at.

In the Loader Model atoms have a hidden and random energy state, and a
detectable state. The energy of light is spread evenly as waves. And when the
energy reaches a threshold the detectable state changes. Photons do not exist.
What we see are just detectable jumps of the energy states.

I never heard of it, until I found an experimenter that claimed to find
evidence for it. With higher levels of energy than normal light, he found that
(more often) two or more atoms can reach a next state, when one quantum of
energy is emitted. Other experimenters classify these double-quanta as
"noise".

Occham's razor?

Because it is the simplest interpretation, I would like to see more research
into this. Maybe there is something to it, or maybe it can reveal some hidden
variables in the detectors.

See: www.threshodmodel.com

Note: the experimenter is not a very good communicator and it took me some
time to understand what he was explaining.

~~~
arnoooooo
The simplest interpretation is that there is no such thing as matter.
Physicists are studying consciousness.

It is actually the only explanation that is consistent with experience, since
there is no experience outside of consciousness.

~~~
eloff
This is a new agey woo kind of idea that comes probably from a layman's
interpretation of the effect of the observer on changing the quantum system
being measured. However, it does not scale to macro systems. As Sam Harris put
it when debating this idea with Deepak Chopra, the moon does not disappear
when we're not looking at it. The universe was before consciousness and will
continue to be afterwards.

~~~
amanaplanacanal
> As Sam Harris put it when debating this idea with Deepak Chopra, the moon
> does not disappear when we're not looking at it.

That’s a silly statement. How do we know that, if we aren’t looking at it?

~~~
homonculus1
Because we have object permanence. People like Deepak Chopra select magical
assumptions specifically because they can't produce any verifiable
predictions, and waste everybody's time promoting meaningless nonsense.

~~~
arnoooooo
I'm not sure Deepak Chopra is the best representative for such ideas. Donald
Hoffman or Bernardo Kastrup make a much more serious case.

But still, the number one unverifiable prediction is that there is a thing
called matter that exists outside consciousness and that somehow,
consciousness emerges out of it. Nobody can prove matter exists, nobody has
ever had a direct experience of it, and nobody has any idea how consciousness
could come out of it, yet it's still the default hypothesis…

------
ReadEvalPost
Direct link to the paper this post sets up:
[https://arxiv.org/abs/1912.06462](https://arxiv.org/abs/1912.06462)

Always been a fan of Superdeterminism, happy to see actual physicists working
on it.

~~~
comboy
If you've always been a fan then maybe you have some more recommended reading
for me? Title of the paper seems to be a bit over the top, it just seems to
counter some straw man arguments against Superdeterminism.

------
iaoat2d
Tim Palmer (the other author of the paper) has a talk[1] on youtube titled
"What Physics Needs is Not So Much a Quantum Theory of Gravity As a
Gravitational Theory of the Quantum" in which he discusses Superdeterminism.

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

------
mikorym
> doesn’t exactly make me feel optimistic about my prospects of getting
> someone to listen to me

Show, don't tell. I don't know how things work in physics (maybe they need a
grant) but in mathematics, if you make a ruckus without any actual
mathematics, then people ignore you. If you have a proof or text that does
something substantial, then people do ignore you at first but in the long run
the best mathematical base of knowledge takes preference.

------
77544cec
> But Tim Palmer turned out to not only be a climate physicist with an
> interest in the foundations of quantum mechanics, he also turned out to be
> remarkably persistent. He wasn’t remotely deterred by my evident lack of
> interest. Indeed, I later noticed he had sent me an email already two years
> earlier. Just that I dumped it unceremoniously in my crackpot folder. Worse,
> I seem to vaguely recall telling my husband that even the climate people now
> have ideas for how to revolutionize quantum mechanics, hahaha.

> Cough.

My favourite crackpot sent her his theory about gravity because she published
a bimetric model of gravity a decade earlier. She accused him of plagiarism.
Full story (french, bad subtitles):
[https://www.youtube.com/watch?v=CKWqh75ErNI&t=40m54s](https://www.youtube.com/watch?v=CKWqh75ErNI&t=40m54s)

Also she made a few music-videos (the music is her own it seems):

[https://www.youtube.com/watch?v=NrswlFxEiV4](https://www.youtube.com/watch?v=NrswlFxEiV4)

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

------
outlace
It's my understanding from reading some of Gerard t'hooft's work on
superdeterminism that a superdeterministic theory underlying quantum mechanics
would mean that quantum computers would be predicted to not have any advantage
over classical computers (given equivalent clock-speed, etc) but Google's
demonstration of quantum supremacy seems to disconfirm this prediction.

------
wsy
Superdeterminism looks like metaphysics to me. It seems an attempt to
postulate a fundamental truth about the world, but without empirical
foundation. Which experiment would falsify the superdeterminism hypothesis?

~~~
gliese1337
The one proposed in the paper: looking for time-dependent correlations in the
measurements of quantum states that are prepared to be as identical as
possible.

------
matt_morgan
"There are only three people in the world who understand Superdeterminism" ...
thinking people would agree with you if they only understood better what you
were saying is a pretty classic rhetorical problem.

------
ouid
Hopefully this doesn't make me seem like a crank, but it seems to me that the
path forward on superdeterminism is to use uncomputability.

1: Untriangulable smooth manifolds exist.

2: The manifolds can be smoothed via Ricci flow in a manner similar to how
Perelman solved the Poincare conjecture.

3: This smoothing, applied to an untriangulable manifold, is irreversible,
deterministic, and yet somehow must not converge to any triangulable manifold.

~~~
ajkjk
I'm having trouble seeing what any of that has to do with determinism.

~~~
ouid
The evolution of a manifold under Ricci flow is deterministic as mentioned,
and it is also irreversible, ie many manifolds are smoothed to the same
manifold. It's also a diffeomorphism, meaning that it preserves all of the
topological information of the manifold that it acts on. Furthermore it can
act on manifolds which have no normal form, in at least some sense. Because
smooth manifolds with no triangulation do indeed exist.

The manifold cannot, in whole, as a result of this, get "simpler" or even
maintain the same amount of simplicity, it must somehow get more complex,
which would require information to be generated. The primary problem with
deterministic models, at least as I understand it, is that there's no obvious
way for deterministic processes to get more complex.

~~~
comex
Aren't diffeomorphisms invertible by definition?

------
beamatronic
It’s humbling to me that there are 7 billion people on this planet. Many of
them are highly educated. And we are running up against problems we can’t
understand. The fundamental nature of the universe.

~~~
ganzuul
I think the problem is anthropocentrism. It's much like the IMO preposterous
and archaic idea that a deity has to resemble us.

People who study the fundamentals of quantum mechanics complain that
philosophy is seen as useless. From my understanding this stems from how in
detail the Copenhagen 'interpretation' took hold in particulary U.S.
institutions; and it is entirely non-scientific. Copenhagen is an engineering
discipline, and not a scientific theory. In natural philosophy we have to
account for our position compared to the object we study. We are not separate
from nature.

Philosophy has many ideas which help us deal with our physical reality and
they need to be taken seriously.

------
okpatil
I am just going to put it here. This wikipedia article is about an ancient
Indian school of thought which believed that everything is composed of atoms,
but the aggregation and nature of these atoms was predetermined by cosmic
forces. They also believed in absense of "Free Will".
[https://en.wikipedia.org/wiki/%C4%80j%C4%ABvika](https://en.wikipedia.org/wiki/%C4%80j%C4%ABvika)

------
mikorym
I'm not sure what exactly the problem is with measurement (Sounds like it is
that physically we don't know what it means?) but current quantum categorical
logic research usually does have a working definition of what they call
measurement.

~~~
GoblinSlayer
In most interpretations measurement is interaction, it's difficult to retain
the rest of Copenhagen interpretation with the definition.

------
viach
But where all the information came from then?

------
mberning
“Should we discover that quantum theory is not fundamentally random”

This would be a terrifying revelation on a personal and existential level.

~~~
throwaway713
> This would be a terrifying revelation on a personal and existential level.

Why is that? I believe the universe is fully deterministic (i.e., no such
thing as "true" randomness), yet I also don't think that rules out free will.
Free will and determinism aren't necessarily incompatible.

~~~
harmoat
> Free will and determinism aren't necessarily incompatible.

How?

~~~
GoblinSlayer
If you don't require free will to be supernatural.

~~~
nateferrero
Right, will is a natural, deterministic feature

------
philip142au
I believe strongly that everything is deterministic. As a programmer, that
means all is purely functional.

~~~
ajkjk
What does it matter what you believe? The universe is evidently somewhat
probabilistic, what's left is explaining the details.

~~~
philip142au
No its deterministic, but it appears to be probabilistic to you. Which it can
be.

------
ncmncm
I _just_ finished reading her book, today. Rock on, Sabine!

Anything that makes believers in Free Will or Consciousness unhappy makes me
happy.

~~~
ganzuul
I'm super curious about people who make this claim. Are you not conscious? The
idea that there are people walking around who look and act like everybody else
but behind the eyes there is _nothing_ is terrifying and exhilarating to me.
I'm open to the idea that when you observe yourself there is nothing looking
back at you, but that doesn't generalize the necessarily subjective
experience.

~~~
trevyn
I think “subjective experience” in the everyday human sense is something that
we learn / are taught to have — we are taught as children that there is this
thing called “me”, how it works, and how to put sensory experiences into its
context.

Unlearning that — understanding that this model is _one_ interpretation, but
not the only interpretation — is indeed terrifying and exhilarating. I
personally wouldn’t call my experience “not conscious”, but it can be a _very_
different experience than what we consider normal everyday waking
consciousness.

~~~
ganzuul
The root of this puzzle is described by Descartes' "I think, therefore I am."
'Thinking' here does not need to be rational thought. Perhaps it does not even
need to be the ability to form new memories. It is hard to say anything
meaningful about the dichotomy of one's personal existence but for the purpose
of my question it should not matter. In altered states of awareness such as
dissociation or 'ego death' this conscious 'eye' which observes one's
experiences remains unchanged. It is not the _idea_ of the self described by
"I am I", but the self which only asserts its own existence as "I am".

~~~
trevyn
In my mind, once you strip down “I am” to “There appears to exist a repeating
neural process that is creating a compressed embedding and record of sensory
inputs”, it’s just not very mysterious or worthy of much further philosophical
analysis.

So these other humans in the world are probably just deterministic robots just
like me, that may or may not feel like they have magic conscious aliveness.

But my personal experience tells me that I can turn the “sense” of magic
conscious aliveness on or off, and so it too is likely just a neural process
that is not particularly interesting.

I observe that the vast majority of other humans do not seem to be able to
disable this sense at will, which does not to me imply that they are somehow
more magically conscious, just that they have not experienced that particular
switch flipping.

Add in the historic social knowledge of “consciousness”, the historical record
of neuroscience knowledge, and the rates at which scientific knowledge is
processed and absorbed by the public at large, and it really seems like an
obvious non-problem.

~~~
ganzuul
That's an absolutely fascinating thing to claim... Your description sounds
like what I have very recently read about research into artificial neural
networks, which would have vast implications for the future of the field.

I have not ever seriously considered the ability to turn consciousness on and
off at will. In my experience consciousness is absolute and once deep in
reverie when I happened upon a mental switch to turn seemingly _everything_
off I instead experienced a brief 'no-mind' blank state and a moment later my
mind basically 'rebooted'. During no-mind, "I am" was definitely there but
there was no thought to reflect this fact. There was an observer with nothing
to observe. Normally, the only interruption to consciousness that I experience
is for the time between wakefulness and dream and for this period I have no
recollection.

Is this no-mind state what you mean by turning off consciousness?

~~~
trevyn
I mean turning off the sense of intention or agency (i.e. “conscious”
decision-making), as well as the sense of self (i.e. self-“consciousness”).
There is still awareness of sensory inputs and memory of events, but there is
no sense of making deliberate choices, personal identification with the
sensory data or events, or emotional response. So there is, for linguistic
convenience, “a body” doing things, but it doesn’t feel like it’s “mine” or
that “I can control it”. Overall it feels lightly dissociative, and I can
carry on normal everyday interactions in this state; it feels like everything
is on auto-pilot and the body knows what to do, probably mostly by habit.

I mention this particular state because it seems to reveal that the feeling of
being an agentic self is a specific construction of mind, and that it can be
intentionally deconstructed while maintaining other brain functions.

There are lots of related directions one can go with this; the “no-mind” state
you mention and the techniques to achieve it are excellent to practice with.

~~~
ganzuul
I understand. However self-consciousness is not what I mean by consciousness.
If you observe 'your' actions there is still something there along for the
ride. It is this which I surmise is common for all humans.

------
acqq
Argh. Reading the announced paper on arxiv
[https://arxiv.org/abs/1912.06462](https://arxiv.org/abs/1912.06462) In the
_introduction_ :

" _Most importantly_ , we will discuss how it may be possible to _test this
hypothesis_ in an (almost) model independent way."

Most. Importantly.

Then in the paper, under "Experimental Test":

"This means concretely that one should make measurements on states prepared as
identically as possible with devices as small and cool as possible in time-
increments as small as possible.

This consideration does not change much if one believes the hidden variables
are properties of the particle after all. In this case, however, the problem
is that preparing almost identical initial states is impossible since we do
not know how to reproduce the particle’s hidden variables. One can then try to
make repeated measurements of non-commuting observables on the same states, as
previously laid out in [36]."

And finally:

"[36] S. Hossenfelder, “Testing super-deterministic hidden variables
theories,” Found. Phys. 41, 1521 (2011) [arXiv:1105.4326 [quant-ph]]."

So after the "most" qualified introduction, eventually just a reference to her
2011 paper. "Most importantly" "good" ... joke?

