A lost Schrödinger manuscript reveals a twist in quantum physics

74 points
1/21/1970
3 days ago
by ibobev

Comments


darkslide3000

It's funny that world-leading physicists were arguing about these questions in the 40s (even if briefly), because I feel like nowadays, everyone who has played Civilization would've intuitively known Whittaker's argument to be flawed (at least those of us that like to savescum). A photon with hidden variables is essentially like playing a game of Civilization with the "preserve random seed" option enabled: if you reload a save and then take the same action (e.g. order unit X to attack unit Y) 100 times, you'll get 100 times the same result (e.g. unit X wins) — just like a deterministic photon would always take the same path. But if you load that same save and then take a different action (e.g. first order unit A to attack unit B, and then order unit X to attack unit Y) you may get a different outcome (e.g. unit X might die), because the PRNG from that same random seed is fed operations in a different order. The result can still be absolutely deterministic, but nevertheless dependent on external inputs. Same for the photon that could start acting differently in a way that is still tied to its hidden variable state when the environment it is confronted with changes (as if each quantum particle was seeded with its own little PRNG).

Of course Bell later proved by experiment that quantum state cannot be explained as simply as a local hidden variable, no matter how it looks like. But these guys didn't know that yet.

2 days ago

aleph_minus_one

> Of course Bell later proved by experiment that quantum state cannot be explained as simply as a local hidden variable, no matter how it looks like.

Bell's theorem does not prove that. An alternative explanation is superdeterminism:

> https://en.wikipedia.org/wiki/Superdeterminism

2 days ago

gus_massa

Superdeterminism is not local, and I also think it's even more weird than the other interpretations.

2 days ago

tancop

It's also not falsifiable at all. Basically the same thing as saying God sets the result of each individual quantum experiment to whatever he wants. There's nothing wrong with believing in one of these things but neither can be a scientific hypothesis.

a day ago

TheOtherHobbes

The premise isn't just determinism, which is already a huge reach, but determinism which just happens to correlate observer choices with experimental results in exactly the way that casts doubt on the meaning of Bell experiments.

"Weird" is underselling it.

2 days ago

naasking

Superdeterminism is local actually, although accepting non-locality is another way to satisfy Bell's theorem that's compatible with hidden variables (Bohmian mechanics/pilot wave theory).

2 days ago

Q_is_4_Quantum

I can make the random setting choices for a Bell experiment by taking two photons from parts of the night sky that have not been in causal contact since very shortly after the big bang (assuming everything was in causal contact right at the big bang - which is reasonable, but I suspect not provable).

So fine - the superdeterminism conspiracy is local iff it can then be carried forwards billions of years in time, ensure that those specially correlated photons were emitted towards the right set of monkeys orbiring this insignificant star, and so on.

Alternatively you could also make the settings choices based on what the Dow Jones finishes on tomorrow and whether or not you personally went to the toilet before it closes. If those really are conspiratorially correlated in just such a way as to fool us into seeing "Bell violations", then why aren't you rich?

If thats the price of "saving locality" I'm not having anything to do with it, and most other physicists feel the same. The superdeterminists are vocal not persuasive.

Of course there are many other challenges (why does science even work if I can never "really" do independent replications of experiments and so on.) Scott Aaronson has a good rant about it somewhere...

21 hours ago

artnap

Schrödinger's fix to Whittaker's photon argument was to let the hidden variable take any value between zero and one, instead of just two. It's funny that such a small change was enough to rebuild the quantum probabilities.

3 days ago

adrian_b

It is not surprising that Schrödinger did this, what is surprising that a competent physicist, as Whittaker should have been, could ever write such an obviously weak "proof".

If there are hidden variables, it is pretty obvious that they cannot be binary variables, but their nature must be that of spins, i.e. rotation movements, where the probability of interaction depends on the instantaneous values of the rotation angles of the interacting particles (which correspond to the phases of the "wave" functions describing the system).

2 days ago

luc4

To give some nuance on the quote "Experimental evidence + logical deduction can never prove that either the deterministic or the indeterministic view is impossible": We can indeed rule out a local hidden variable model [1].

So if the deterministic view is true, then it has to be a holistic theory. The hidden variables must be global, i.e. "accessible" throughout the universe. They cannot be attached to a particle as in Whittaker's model or Schrödinger's modification.

[1] https://en.wikipedia.org/wiki/CHSH_inequality

2 days ago

birdland

There is another out, Bell assumes markovianity(The sum across conditional probabilities requires divisibility), the discrepancy disappears if the particle trajectories while unmeasured are non-markovian/indivisible. See the work of Jacob Barandes. This view allows for determinism just fine and does not require ftl communication or global constraints.

2 days ago

adrian_b

The CHSH or Bell inequalities are based on quite dubious assumptions that seem a poor match for how real hidden variables should behave and the current quantum mechanics is still full of inconsistencies.

Much of the classic quantum mechanics, e.g. based on the Schrödinger or Dirac equations, is compatible with local hidden variables and I have not seen yet a precise account of which are the more recent axioms/assumptions that introduce an incompatibility with local hidden variables.

Thus I do not believe that the non-existence of local hidden variables has been proven beyond any reasonable doubt.

2 days ago

sgdpk

What are the dubious assumptions in your opinion?

The GHZ/Mermin experiment refined the Bell argument into an "all-or-nothing" experiment with three parties. In that scenario, there are no probabilistic tests. Alice, Bob and Charlie each receive one particle (entangled, of course) and make a local decision to measure one of two quantities of that particle: x or y, each with a binary outcome. The decision to measure x or y is local and beyond the light cone of influence of each.

No matter what they chose to measure, the results are strongly correlated. So much so, that it is clear that you cannot predict every outcome of what the three parties measure. There just isn't a single pre-determined logically consistent assignment of outcomes before the actual measurement (there is a parity restriction of the outcomes).

But the measurements are consistent anyway. So, either there is faster-than-light communication which enforces the consistency, or indeed the outcomes cannot be decided until one of them measures something. It just isn't mathematically possible.

This is also independent of the physical theory by the way. You don't need Schroedinger, Dirac, or anything. Any physical theory that predicts measurements just like QM would will have this restriction. So hidden variables are incompatible with locality (no faster-than-light communication).

2 days ago

adrian_b

The experiments are fine and useful for constraining any better interpretation.

The problems are in their interpretation and in the interpretation of much of the formalism of quantum mechanics and quantum field theory.

There are far more possible interpretations that match the known experimental facts than it would appear from university textbooks.

The problem is that for now it is not possible to decide which of them is right, because nobody has been able to work out their complete consequences by creating a complete coherent quantum theory.

There are a lot of alternative interpretations that sound more plausible than the mainstream interpretation, but none of them has been developed enough to be able to prove that they could explain everything.

This is a subject that requires a book-length treatment. There are actually some such books, but they only show the very serious flaws of the mainstream interpretation of quantum theory, without being able to propose an adequate complete replacement. Criticism is always easier than discovering a better solution.

The only certitude is that the current quantum mechanics/quantum field theory are not the final theories of physics and whoever believes that physics is solved is as naive as those who believed the same thing at the end of the 19th century.

2 days ago

lostmsu

So what are the "dubious assumptions"?

a day ago

Lumich

[dead]

2 days ago

My_Name

[dead]

2 days ago

[deleted]
2 days ago

hackandthink

Robert W. Spekkens (and I guess Matt Leifer) tried to model quantum uncertainty classically.

(my gut feeling was: it works till it does not work)

"In defense of the epistemic view of quantum states: a toy theory"

https://arxiv.org/abs/quant-ph/0401052

2 days ago

rramadass

Great article on an interesting topic.

The article mentions the great Physicist, Prof. S.N.Bose's take in a lecture delivered to the Indian Science Congress in 1944. It is titled "The Classical Determinism and The Quantum Theory".

The corresponding pdf can be found at Prof.S.N.Bose archive under Section 6 "Documents" titled "Presidential address at the Indian Science Congress, Delhi,1944 [Current Science, Vol XIII, No. 1]" - https://www.bose.res.in/Prof.S.N.Bose-Archive/

Prof. S.N.Bose is the Physics great after whom "Bosons", "Bose-Einstein Statistics", "Bose-Einstein Condensate" and even "Higgs Boson" are named - https://en.wikipedia.org/wiki/Satyendra_Nath_Bose

3 days ago

srean

I find SN Bose's derivation of quantized distribution of energy levels so much more elegant than Plank's which reads more like a desperate hack to force a predetermined answer.

3 days ago

rramadass

Wikipedia has a telling quote from the Physicist, Prof. Partha Ghose;

Bose's work stood at the transition between the 'old quantum theory' of Planck, Bohr and Einstein and the new quantum mechanics of Schrödinger, Heisenberg, Born, Dirac and others.

I have always felt that Prof.S.N.Bose never got full credit and acclaim for his achievements maybe because there were so many other greats at that time though Einstein recognized his originality.

3 days ago

adrian_b

I agree, and it is likely that without the support of Einstein his work might have remained ignored.

Nonetheless, nowadays the distinction between bosons and fermions is one of the most important facts of physics, as important as the fact that there exists a maximum velocity. The structure of all matter depends in an essential way on this fact.

So the memory of Bose might be preserved forever, whenever bosons are mentioned.

2 days ago

rramadass

It was Paul Dirac who coined the terms "Bosons" (in honour of S.N.Bose) and "Fermions" (in honour of Enrico Fermi). Given that they follow different statistical models (i.e. Bose-Einstein vs. Fermi-Dirac) he too realized Bose's original genius contributions.

And of course the "god particle" aka "Higgs Boson" is named partly after him ;-)

It is a shame he never received the Nobel Prize for Physics.

See also https://news.ycombinator.com/item?id=50195940

2 days ago

wolfi1

Planck admitted it himself that it was a hack he just postulated that there had to be quants. It was Einstein when he explained 1905 the photoelectric effect that quanta were accepted as "real"

2 days ago

rramadass

Prof. Partha Ghose in his paper The Story of Bose, Photon Spin and Indistinguishability does a nice walkthrough of Bose's derivation - https://news.ycombinator.com/item?id=50195940

2 days ago

yonisto

I was hoping it established that the cat is ginger

2 days ago

sota_pop

I was under the impression it was already established that the cat is both ginger and not-ginger?

2 days ago

readthenotes1

A good example of a monster whose professional life benefits the world.

Worth the cost? I'd say not, but I'm generally an optimist.

2 days ago

abbadadda

Why was Schrödinger a monster in his personal life?

2 days ago

dabiged

The guy was a paedophile and justified it because he was so intelligent he deserved to sleep with children.

2 days ago

adrian_b

Any human may have contradictory and uncorrelated aspects of personality, but nonetheless I find too difficult to believe such accusations.

Besides physics texts, Schrödinger has also written some more philosophical texts, which are very good and which show much more common sense than for many other physicists, past or present. The qualities of those texts seem quite incompatible with a deviant personality, like that of a paedophile.

In the absence of any concrete evidence, with all accusations based just on vague hearsay, I believe that it is much more likely that an accuser who has never done anything worthwhile is wrong, either non-intentionally or intentionally, than that the accused person, with a lifetime of great achievements, is guilty.

Moreover, even if the accusations of relations with young girls had been true, calling him a "paedophile" would not have been necessarily correct. What is classified as a paedophile in modern USA was not necessarily classified as such in other countries one century ago. In the past most European countries had much lower ages of consent than today, typically as low as 14 years.

"The guy was a paedophile and justified it" is a false sentence, because he certainly never admitted such a thing. The accusations were made post-mortem, based on hearsay, when he was no longer able to defend himself.

2 days ago

wolfi1

it was never proven in a court of law, nor have there been accusations of any kind in this regard in his lifetime. it seems that Moore couldn't read Schrödinger's shorthand and he had to rely on other sources [0] [0]https://science.orf.at/stories/3237287/

2 days ago

danbruc

I had never heard that and just had a look at the Wikipedia article and those claims seem to be primarily based on one biography. Other research based on his journals disputes the image portrayed in the Moore biography.

2 days ago

Y_Y

It's "common knowledge" that that's why he ended up in Dublin

2 days ago

pezezin

He moved to Ireland in 1939. I am sure you are aware of certain events going on in Europe at that time that might have pushed him to leave Austria, as so many other famous scientists did...

2 days ago

Y_Y

But they didn't all end up in a backwater like Ireland. Starting DIAS is cool, but presumably he'd have preferred the US.

9 hours ago

adrian_b

Such strong accusations cannot be done based on "common knowledge".

They must be based on identified witness testimonies, to have any kind of validity.

2 days ago

Y_Y

This isn't a court, I'm just saying that such a thing is rumoured

2 days ago

naasking

It is crazy how readily people believe wild accusations with little credible evidence though. Not addressed at you specifically, just this whole subthread is wild.

2 days ago

d--b

There is a world out there in which the manuscript was not lost.

2 days ago

euroderf

Can this shed light on determinism v free will ?

2 days ago

rramadass

The Classical Determinism and The Quantum Theory - https://news.ycombinator.com/item?id=50195940

In a sense, "Indeterminism" implied by probabilities at the quantum level can be said to give rise to "Free Will" as the strict chain of cause and effect is broken at the fundamental level. Since there are multiple possible outcomes from the same starting conditions, "Consciousness" may be the causal agent (Observer?) which selects one of the possible outcomes i.e. "choice due to free will". Think of it as Physics leaving all options open for an event (within bounds) and Consciousness selecting one among the set. Since the probabilities must add up to one, at the aggregate macro level it is predictable and deterministic while being unpredictable and indeterministic at the quantum micro level.

2 days ago

euroderf

This makes sense and is self-consistent. But you speak of one single item in the range [0.0,1.0]. Might one speak of thousands - of millions - even of multitudes ? The "aggregate macro level" can be a combinatorial explosion of beauties and horrors.

You also imply (I think) that there is a finite space (bounded) for a variable to range in. Analogous to an LLM spanning and recombining its training materials. But what of the infinite - the unknown ? Of course one might say that we as hoominz are similarly bounded - that we are a variety of wetware LLM, limited by our own training materials (i.e. genes + sensory inputs + generated mental experiences).

But being of a spiritual bent myself, I ask: Where is the foot in the door for the divine ? Knocking at the door of fundamental unknowability - as you say, "unpredictable and indeterministic at the quantum micro level". If there is an intangible, immaterial element to our existence - call it a "soul" - then we might have identified the interface where "the rubber meets the road".

Obv others have considered this question at great length and in great depth.

2 days ago

rramadass

> Might one speak of thousands - of millions - even of multitudes ? The "aggregate macro level" can be a combinatorial explosion of beauties and horrors.

By "aggregate macro level" I mean the averaging out of aggregate probabilities of multitudes of random events. This is what gives rise to an emergent predictability and determinism which we perceive as certainty. One way to understand this is; For any one event its aggregate probabilities must sum to one thus making it certain within its outcome space. This is carried forward when you consider (as you put it) "a combinatorial explosion" of multitudes of random events.

> You also imply (I think) that there is a finite space (bounded) for a variable to range in. Analogous to an LLM spanning and recombining its training materials. But what of the infinite - the unknown ?

Your comparison of random variables in quantum theory with random variables in LLMs is a bit far-fetched but there certainly are some parallels in the usage of probability distributions in a information-theoretic sense (including infinity).

> Of course one might say that we as hoominz are similarly bounded - that we are a variety of wetware LLM, limited by our own training materials (i.e. genes + sensory inputs + generated mental experiences).

W.r.t. Humans vs. LLMs one needs to bring together; a) A study of Language as being indistinguishable from the "Reality" it describes. b) A study of psychological theories like "Self-Determination Theory" (SDT), "Operant Conditioning", "Behaviourism" and finally, c) Neurobiology which gives rise to what we call "emergent Consciousness". Humans are not just a variety of "wetware LLM".

> But being of a spiritual bent myself, I ask: Where is the foot in the door for the divine ? Knocking at the door of fundamental unknowability - as you say, "unpredictable and indeterministic at the quantum micro level". If there is an intangible, immaterial element to our existence - call it a "soul" - then we might have identified the interface where "the rubber meets the road".

Now we are in the philosophical realm. At the human level we have the various schools of philosophy of which the dualistic Hindu school of "Samkhya" is a good model to study and seek mappings from. According to this school, there is a constant/unchanging/attributeless "Consciousness" (which in materialistic science we can map to an "Emergent Property" of a complex system that is the total Human Organism) and no "divinity" outside of you. Complementing it is the "External Reality" which includes everything else both material(matter etc.)/immaterial(your thoughts/feelings etc.) and which is constantly changing/evolving dynamically over time. It is said that "Consciousness Observes/Witnesses Reality".

This directly parallels quantum theory where the Observer and the Object are entangled into one system during the act of Observation/Measurement though they are separate. This entanglement is what you could call (roughly) "The Mind" where you build Reality i.e. collapse of the possibilities into a single result.

The above is one of the reasons that most Quantum Physicists were quite enamoured of and studied the various Hindu schools of philosophy since there were many parallels here.

Finally, at the Physics level see the excellent "Physics and Philosophy by Werner Heisenberg" for a nice exploration.

2 days ago

mark_something

If indeterminism gives us free will, it's like making a decision by rolling dice. I wouldn't call that free will.

One explanation that I heard of free will is that it depends on the complexity of a system. A simpler being might think it had free will while it is predictable to us because we see how it works. A much more complex being might be able to predict what we will do.

2 days ago

naasking

Free will is almost certainly compatible with determinism (cf. Compatibilism).

2 days ago

euroderf

Oh my, me gots some new reading material :)

2 days ago

naasking

Just think of it intuitively: we don't hold babies or the insane responsible for their choices partly because they act randomly with no rhyme or reason, but you become responsible for your choices as you grow and your choices become more understandable and predictable in a way; in some real sense, you're more responsible the more deterministic you are!

2 days ago

ChrisMarshallNY

They found his cat?

-I'll get my coat...

2 days ago

ziiinq

[dead]

2 days ago

justauserid

I just want to know what happened to the cat, eventually. Like for real – beyond the (academic) (un)certainties.

2 days ago

moehm

70 years later they looked it up and the cat is definitely dead.

2 days ago

wolfi1

Didn't you read Dirk Gently's Holistic Detective Agency?

2 days ago