Saturday, October 19, 2019

Google overhyped announcement imminent

Nautilus:
News on the quantum physics grapevine, Frankfurt Institute theoretical physicist Sabine Hossenfelder tells me, is that Google will announce something special next week: Their paper on achieving quantum supremacy, the realization of a quantum computer that outdoes its conventional counterpart. ...

It’s nothing to get too excited about yet. “This” — NISQ — “is really a term invented to make investors believe that quantum computing will have practical applications in the next decades or so,” Hossenfelder says. “The trouble with NISQs is that while it is plausible that they soon will be practically feasible, no one knows how to calculate something useful with them.” Perhaps no one ever will. “I am presently quite worried that quantum computing will go the same way as nuclear fusion, that it will remain forever promising but never quite work.”
We know that the Sun gets its energy from nuclear fusion. We don't know that quantum speedups are even possible.

Thursday, October 17, 2019

Rovelli: Neither Presentism nor Eternalism

Physicist Carlo Rovelli writes in support of Neither Presentism nor Eternalism:
Shortly after the formulation of special relativity, Einstein's former math professor Minkowski found an elegant reformulation of the theory in terms of the four dimensional geometry that we call today Minkowski space. Einstein at first rejected the idea. (`A pointless mathematical complication'.) But he soon changed his mind and embraced it full heart, making it the starting point of general relativity, where Minkowski space is understood as the local approximation to a 4d, pseudo-Riemannian manifold, representing physical spacetime.

The mathematics of Minkowski and general relativity suggested an alternative to Presentism: the entire 4d spacetime is `equally real now', and becoming is illusory. This I call here Eternalism.
Other make this argument that relativity implies a eternalism philosophy of time. I disagree with this argument. You can talk about spacetime with either Galilean or Lorentz transformations. If that is eternalist, then it is either with or without relativity.

Note that Rovelli is compelled to make his relativity story all about Einstein, even tho he had nothing to do with the issue at hand. Minkowski did not reformulate Einstein's theory, as it is not clear that Minkowski was ever influenced by anything Einstein wrote. Spacetime relativity was first published by Poincare, and Minkowski cited Poincare.

Rovelli ends up wanting some compromise between presentism and eternalism, as both views are really just philosophical extremes to emphasize particular ways of thinking about time. This might seem obvious, except that there are a lot of physicists who say that relativity requires eternalism.

Monday, October 14, 2019

The hardest of the hard sciences has gone soft

Science writer Jim Baggott writes in Aeon:
So what if a handful of theoretical physicists want to indulge their inner metaphysician and publish papers that few outside their small academic circle will ever read? But look back to the beginning of this essay. Whether they intend it or not (and trust me, they intend it), this stuff has a habit of leaking into the public domain, dripping like acid into the very foundations of science. The publication of Carroll’s book Something Deeply Hidden, about the Many-Worlds interpretation, has been accompanied by an astonishing publicity blitz, including an essay on Aeon last month. A recent PBS News Hour piece led with the observation that: ‘The “Many-Worlds” theory in quantum mechanics suggests that, with every decision you make, a new universe springs into existence containing what amounts to a new version of you.’

Physics is supposed to be the hardest of the ‘hard sciences’. It sets standards by which we tend to judge all scientific endeavour. And people are watching.
Physics has become embarrassingly unscientific.

Unsurprisingly, the folks at the Discovery Institute, the Seattle-based think-tank for creationism and intelligent design, have been following the unfolding developments in theoretical physics with great interest. The Catholic evangelist Denyse O’Leary, writing for the Institute’s Evolution News blog in 2017, suggests that: ‘Advocates [of the multiverse] do not merely propose that we accept faulty evidence. They want us to abandon evidence as a key criterion for acceptance of their theory.’ The creationists are saying, with some justification: look, you accuse us of pseudoscience, but how is what you’re doing in the name of science any different?
Yes, I think it is different. The folks at the Discovery Institute try to support their ideas with evidence. Carroll has no evidence for his ideas, and denies that any evidence is needed.
Instead of ‘the multiverse exists’ and ‘it might be true’, is it really so difficult to say something like ‘the multiverse has some philosophical attractions, but it is highly speculative and controversial, and there is no evidence for it’?
No, many worlds is not some speculative idea that might be true. Saying that would suggest that there might be evidence for it. There can be no evidence for it.

Sabine Hossenfelder writes:
Right, as I say in my public lecture, physicists know they shouldn't make these arguments, but they do it nevertheless. That's why I am convinced humans will go extinct in the next few hundred years.
Extinct? Maybe rational humans will die out, and be replaced by intelligent robots and an uneducated underclass.

Wednesday, October 9, 2019

Preskill explains quantum supremacy

Physicist John Preskill writes in Quillette:
In 2012, I proposed the term “quantum supremacy” to describe the point where quantum computers can do things that classical computers can’t, regardless of whether those tasks are useful. ...

The words “quantum supremacy” — if not the concept — proved to be controversial for two reasons. One is that supremacy, through its association with white supremacy, evokes a repugnant political stance. The other reason is that the word exacerbates the already overhyped reporting on the status of quantum technology.
This is funny. A few years ago, supremacy might have invoked thoughts of kings, empires, popes, and laws, but not white people. Now rationalist internet forums get frequented by misogynists and white nationalists. Preskill seems to be referring to this gripe about white supremacy.
The catch, as the Google team acknowledges, is that the problem their machine solved with astounding speed was carefully chosen just for the purpose of demonstrating the quantum computer’s superiority. It is not otherwise a problem of much practical interest. In brief, the quantum computer executed a randomly chosen sequence of instructions, and then all the qubits were measured to produce an output bit string. This quantum computation has very little structure, which makes it harder for the classical computer to keep up, but also means that the answer is not very informative.

However, the demonstration is still significant. By checking that the output of their quantum computer agrees with the output of a classical supercomputer (in cases where it doesn’t take thousands of years), the team has verified that they understand their device and that it performs as it should. Now that we know the hardware is working, we can begin the search for more useful applications.
The term "quantum supremacy" suggests a major accomplishment. But all we really know is that the hardware is working.

We also know that they did a quantum experiment that is hard to simulate. But so what? The weather is hard to simulate. A lot of things are hard to simulate.

Here is Preskill's 2012 paper on quantum supremacy, and 2018 paper on NISQ. The latter says:
I’ve already emphasized repeatedly that it will probably be a long time before we have fault-tolerant quantum computers solving hard problems. ...

Nevertheless, solving really hard problems (like factoring numbers which are thousands of bits long) using fault-tolerant quantum computing is not likely to happen for a while, because of the large number of physical qubits needed. To run algorithms involving thousands of protected qubits we’ll need a number of physical qubits which is in the millions, or more [56].
So a quantum computer that tells us something we didn't already know is decades away. Or impossible.

Monday, October 7, 2019

Many-Worlds does not solve measurement

Dr. Bee has a podcast on The Trouble with Many Worlds:
The measurement process therefore is not only an additional assumption that quantum mechanics needs to reproduce what we observe. It is actually incompatible with the Schrödinger equation.

Now, the most obvious way to deal with that is to say, well, the measurement process is something complicated that we do not yet understand, and the wave-function collapse is a placeholder that we use until we will figured out something better.

But that’s not how most physicists deal with it.
Actually, I think it is. Quantum mechanics was created by positivists, and their attitude is to go with what we've got, and not worry too much about purely philosophical objections.
Most sign up for what is known as the Copenhagen interpretation, that basically says you’re not supposed to ask what happens during measurement. In this interpretation, quantum mechanics is merely a mathematical machinery that makes predictions and that’s that. The problem with Copenhagen – and with all similar interpretations – is that they require you to give up the idea that what a macroscopic object, like a detector does should be derivable from theory of its microscopic constituents.

If you believe in the Copenhagen interpretation you have to buy that what the detector does just cannot be derived from the behavior of its microscopic constituents.
The positivists would go along with saying that the theory is all about the predictions, but would never say that you are not supposed to ask about the measurement process. Positivists do not tell you what not to do. They talk about what works.

She is completely correct that the collapse is observed. Some people complain that Copenhagen is goofy because the collapse is unnatural, but all interpretations have to explain the apparent collapse somehow.
The many world interpretation, now, supposedly does away with the problem of the quantum measurement and it does this by just saying there isn’t such a thing as wavefunction collapse. Instead, many worlds people say, every time you make a measurement, the universe splits into several parallel words, one for each possible measurement outcome. This universe splitting is also sometimes called branching. ...

And because it’s the same thing you already know that you cannot derive this detector definition from the Schrödinger equation. It’s not possible. What the many worlds people are now trying instead is to derive this postulate from rational choice theory. But of course that brings back in macroscopic terms, like actors who make decisions and so on. In other words, this reference to knowledge is equally in conflict with reductionism as is the Copenhagen interpretation.

And that’s why the many worlds interpretation does not solve the measurement problem and therefore it is equally troubled as all other interpretations of quantum mechanics.
She is right that Many-Worlds does not solve the measurement problem, and really has to have its own sneaky collapse postulate like Copenhagen, even tho the whole point of Many-Worlds was to avoid that.

However the situation with Many-Worlds is worse than that. Any physical theory could be turned into a Many-Worlds theory by simply introducing a universe splitting for each probabilistic prediction. This can be done with Newtonian celestial mechanics, electromagnetism, relativity, or anything else.

With any of these Many-Worlds theories, you can believe in them if you want, but the split universes have no observable consequences except to reduce or kill the predictive power of your theory. Any freak event can be explained away by splitting to another universe.

So Many-Worlds does not, and cannot, explain anything. It is just smoke and mirrors.

A reader asks:
What is your explanation as to why many people who are obviously very smart, such as Max Tegmark, David Deutsch, Sean Carroll, etc, subscribe to the many-worlds interpretation?
Why do so many smart people tell lies about Donald Trump every day?

I wrote a whole book on how Physics has lost its way. There is now a long list of subjects where prominent Physics professors recite nonsense. I hesitate to say that they are all con men, as many appear to be sincerely misguided.

Friday, October 4, 2019

Google scooped by unconventional p-bit computer

It is funny how quantum computing evangelist Scott Aaronson is flummoxed by being scooped by a rival technology:
Nature paper entitled Integer factorization using stochastic magnetic tunnel junctions (warning: paywalled). See also here for a university press release.

The authors report building a new kind of computer based on asynchronously updated “p-bits” (probabilistic bits). A p-bit is “a robust, classical entity fluctuating in time between 0 and 1, which interacts with other p-bits … using principles inspired by neural networks.” They build a device with 8 p-bits, and use it to factor integers up to 945. They present this as another “unconventional computation scheme” alongside quantum computing, and as a “potentially scalable hardware approach to the difficult problems of optimization and sampling.”

A commentary accompanying the Nature paper goes much further still — claiming that the new factoring approach, “if improved, could threaten data encryption,” and that resources should now be diverted from quantum computing to this promising new idea, one with the advantages of requiring no refrigeration or maintenance of delicate entangled states. (It should’ve added: and how big a number has Shor’s algorithm factored anyway, 21? Compared to 945, that’s peanuts!)

Since I couldn’t figure out a gentler way to say this, here goes: it’s astounding that this paper and commentary made it into Nature in the form that they did. This is funny. While Google is keeping mum in order to over-dramatize their silly result, a rival group steals the spotlight with non-quantum technology.

Aaronson is annoyed that this is non-quantum technology making extravagant claims, but exactly how is the Google quantum computer effort any better?

Apparently Google refuses to compete in any meaningful way, as Aaronson says
How large a number Google could factor, by running Shor’s algorithm on its current device, is a semi-interesting question to which I don’t know the answer. My guess would be that they could at least get up to the hundreds, depending on how much precompilation and other classical trickery was allowed. The Google group has expressed no interest in doing this, regarding it (with some justice) as a circus stunt that doesn’t showcase the real abilities of the hardware.
A circus stunt? Obviously the results would be embarrassingly bad for Google.

Others have claimed to use quantum computers to factor 15 or , but those were circus stunts. They failed to show any evidence of a quantum speedup.

An interesting quantum computer result would factor numbers with Shor's algorithm, and show how the work scales with the size of the number.

Also:
But as I explained in the FAQ, running Shor to factor a classically intractable number will set you back thousands of logical qubits, which after error-correction could translate into millions of physical qubits. That’s why no can do it yet.
And that is why we will not see true quantum supremacy any time soon. All Google has is a fancy random number generator.

Thursday, October 3, 2019

How there is mathematical pluralism

Mathematics is the study of absolute truth.

It is common for non-mathematicians to try to deny this. Sometimes they give arguments like saying that Goedel proved that mathematical truth is not possible. Goedel would never have agreed to that.

Mathematician Timothy Chow writes:
I would say that virtually all professional mathematicians agree that questions of the form “Does Theorem T provably follow from Axioms A1, A2, and A3?” have objectively true answers. ...

On the other hand, when it comes to the question of whether Axioms A1, A2, and A3 are true, then I think we have (what I called) “pluralism” in mathematics.
That is correct.

There are some axioms for the existence of very large cardinals, and some disagreement among mathematicians about whether those axioms should be regarded as true. But there is not really any serious disagreement about the truth of published theorems.

Other fields, like Physics, are filled with disputes about what is true.

Monday, September 30, 2019

Classical and quantum theories are similarly indeterministic

Nearly everyone accepts the proposition that classical mechanics is deterministic, while quantum mechanics is probabilistic. For example, a recent Quanta mag essay starts:
In A Philosophical Essay on Probabilities, published in 1814, Pierre-Simon Laplace introduced a notorious hypothetical creature: a “vast intelligence” that knew the complete physical state of the present universe. For such an entity, dubbed “Laplace’s demon” by subsequent commentators, there would be no mystery about what had happened in the past or what would happen at any time in the future. According to the clockwork universe described by Isaac Newton, the past and future are exactly determined by the present. ...

A century later, quantum mechanics changed everything.
I believe that this view is mistaken.

I don't just mean that some classical theories use probability, like statistical mechanics. Or that quantum mechanics sometimes predicts a sure result.

I mean that determinism is not a genuine difference between classical and quantum mechanics.

A couple of recent papers by Flavio Del Santo and Nicolas Gisin make this point.

One says:
Classical physics is generally regarded as deterministic, as opposed to quantum mechanics that is considered the first theory to have introduced genuine indeterminism into physics. We challenge this view by arguing that the alleged determinism of classical physics relies on the tacit, metaphysical assumption that there exists an actual value of every physical quantity, with its infinite predetermined digits (which we name "principle of infinite precision").
Also:
Classical physics is generally regarded as deterministic, as opposed to quantum mechanics that is considered the first theory to have introduced genuine indeterminism into physics. We challenge this view by arguing that the alleged determinism of classical physics relies on the tacit, metaphysical assumption that there exists an actual value of every physical quantity, with its infinite predetermined digits (which we name "principle of infinite precision"). Building on recent information-theoretic arguments showing that the principle of infinite precision (which translates into the attribution of a physical meaning to mathematical real numbers) leads to unphysical consequences, we consider possible alternative indeterministic interpretations of classical physics. We also link those to well-known interpretations of quantum mechanics. In particular, we propose a model of classical indeterminism based on "finite information quantities" (FIQs). Moreover, we discuss the perspectives that an indeterministic physics could open (such as strong emergence), as well as some potential problematic issues. Finally, we make evident that any indeterministic interpretation of physics would have to deal with the problem of explaining how the indeterminate values become determinate, a problem known in the context of quantum mechanics as (part of) the ``quantum measurement problem''. We discuss some similarities between the classical and the quantum measurement problems, and propose ideas for possible solutions (e.g., ``collapse models'' and ``top-down causation'').
Another:
Do scientific theories limit human knowledge? In other words, are there physical variables hidden by essence forever? We argue for negative answers and illustrate our point on chaotic classical dynamical systems. We emphasize parallels with quantum theory and conclude that the common real numbers are, de facto, the hidden variables of classical physics. Consequently, real numbers should not be considered as "physically real" and classical mechanics, like quantum physics, is indeterministic.
The point here is that any deterministic theory involving real numbers becomes indeterministic if you use finitary measurements and representations of those reals. In practice, all those theories are indeterministic.

Also, any indeterministic theory can be made deterministic by including the future observables in the present state. Quantum mechanical states are usually unknowable, and people accept that, so one could add the future (perhaps unknowable) being in the present state.

Thus whether a physical theory is deterministic is just an artifact of how the theory is presented. It has no more meaning than that.

Tuesday, September 24, 2019

Did Google achieve Quantum Supremacy?

I have readers turning to my blog to see if I have shut it because of the humiliation of being proven wrong.

I refer to papers announcing that Google has achieve quantum supremacy. You can find links to the two papers in the comments on Scott Aaronson's blog.

I am not conceding defeat yet. First, Google has withdrawn the papers, and refuses to say whether it has a achieved a breakthru or not. Second, outside experts like Aaronson have apparently been briefed on the work, but refuse to comment on it. And those who do comment are not positive:
However, the significance of Google’s announcement was disputed by at least one competitor. Speaking to the FT, IBM’s head of research Dario Gil said that Google’s claim to have achieved quantum supremacy is “just plain wrong.” Gil said that Google’s system is a specialized piece of hardware designed to solve a single problem, and falls short of being a general-purpose computer, unlike IBM’s own work.
Gil Kalai says that the Google and IBM results are impressive, but he still believes that quantum supremacy is impossible.

So it may not be what it appears to be.

Aaronson had been sworn to secrecy, and now considers the Google work a vindication of his ideas. He stops short of saying that it proves quantum supremacy, but he implies that the quantum supremacy skeptics have been checkmated.

Probably Google is eager to make a big splash about this, but is getting the paper published in Science or Nature, and those journals do not like to be scooped. The secrecy also helps suppress criticism, because the critics usually don't know enuf about the work when the reporters call.

The paper claims quantum supremacy on the basis of doing a computation that would have been prohibitive on a classical supercomputer.

That sounds great, but since the computation was not replicated, how do we know that it was done correctly?

Wikipedia says:
A universal quantum simulator is a quantum computer proposed by Yuri Manin in 1980[4] and Richard Feynman in 1982.[5] Feynman showed that a classical Turing machine would experience an exponential slowdown when simulating quantum phenomena, while his hypothetical universal quantum simulator would not. David Deutsch in 1985, took the ideas further and described a universal quantum computer.
So we have known since 1982 that simulating a quantum experiment on a classical computer can take exponential time.

At first glance, it appears that Google has only verified that. It did some silly quantum experiment, and then showed that the obvious classical simulation of it would take exponential time.

Is that all Google has done? I haven't read the paper yet, so I don't know. It is hard to believe that Google would claim quantum supremacy if that is all it is. And Google has not officially claimed it yet.

The paper says:
The benchmark task we demonstrate has an immediate application in generating certifiable random numbers [9];
Really? Is that all? It would be more impressive if they actually computed something.

Monday, September 23, 2019

Debunking Libet's free will experiment

The anti-free-will folks often cite a famous experiment by Libet. It doesn't really disprove free will, but it seemed to show that decisions had an unconscious element.

Now I learn that the experiment has been debunked anyway. The Atlantic mag reports:
Twenty years later, the American physiologist Benjamin Libet used the Bereitschaftspotential to make the case not only that the brain shows signs of a decision before a person acts, but that, incredibly, the brain’s wheels start turning before the person even consciously intends to do something. Suddenly, people’s choices—even a basic finger tap—appeared to be determined by something outside of their own perceived volition. ...

This would not imply, as Libet had thought, that people’s brains “decide” to move their fingers before they know it. Hardly. Rather, it would mean that the noisy activity in people’s brains sometimes happens to tip the scale if there’s nothing else to base a choice on, saving us from endless indecision when faced with an arbitrary task. The Bereitschaftspotential would be the rising part of the brain fluctuations that tend to coincide with the decisions. This is a highly specific situation, not a general case for all, or even many, choices. ...

When Schurger first proposed the neural-noise explanation, in 2012, the paper didn’t get much outside attention, but it did create a buzz in neuroscience. Schurger received awards for overturning a long-standing idea.
This does not resolve the issue of free will, but it does destroy one of the arguments against free will.

It also throws into doubt the idea that we subconsciously make decisions.

Saturday, September 21, 2019

On the verge of quantum supremacy again

July news:
Google expected to achieve quantum supremacy in 2019: Here’s what that means

Google‘s reportedly on the verge of demonstrating a quantum computer capable of feats no ordinary classical computer could perform. The term for this is quantum supremacy, and experts believe the Mountain View company could be mere months from achieving it. This may be the biggest scientific breakthrough for humanity since we figured out how to harness the power of fire. ...

Experts predict the advent of quantum supremacy – useful quantum computers – will herald revolutionary advances in nearly every scientific field. We’re talking breakthroughs in chemistry, astrophysics, medicine, security, communications and more. It may sound like a lot of hype, but these are the grounded predictions. Others think quantum computers will help scientists unlock some of the greater mysteries of the cosmos such as how the universe came to be and whether life exists outside of our own planet.
It seems as if I post these stories every year. Okay, here we go again.

I am betting Google will fail again. Check back on Dec. 31, 2019.

If Google delivers as promised, I will admit to being wrong. Otherwise, another year of phony promises will have passed.

Maybe already. The Financial Times is reporting:
Google claims to have reached quantum supremacy
The article is behind a paywall, so that's all I know. If true, you can be sure Google will be bragging in a major way. (Update: Read the FT article here.)

Update: LuMo tentatively believes it:
Google's quantum computing chip Bristlecone – that was introduced in March 2018 – has arguably done a calculation that took 3 minutes but it would take 10,000 years on the IBM's Summit, the top classical supercomputer as of today. I know nothing about the details of this calculation. I don't even know what amount of quantum error correction, if any, is used or has to be used for these first demonstrations of quantum supremacy.

If you have a qualified guess, let us know – because while I have taught quantum computing (in one or two of the lectures of QM) at Harvard, I don't really have practical experience with the implementation of the paradigm.

If true, and I tend to think it's true even though the claim is remarkable, we are entering the quantum computing epoch.
I look forward to the details being published. Commenter MD Cory suggests that I have been tricked.

Friday, September 20, 2019

Physicists confusing religion and science

Sabine Hossenfelderwrites in a Nautilus essay:
And finally, if you are really asking whether our universe has been programmed by a superior intelligence, that’s just a badly concealed form of religion. Since this hypothesis is untestable inside the supposed simulation, it’s not scientific. This is not to say it is in conflict with science. You can believe it, if you want to. But believing in an omnipotent Programmer is not science—it’s tech-bro monotheism. And without that Programmer, the simulation hypothesis is just a modern-day version of the 18th century clockwork universe, a sign of our limited imagination more than anything else.

It’s a similar story with all those copies of yourself in parallel worlds. You can believe that they exist, all right. This belief is not in conflict with science and it is surely an entertaining speculation. But there is no way you can ever test whether your copies exist, therefore their existence is not a scientific hypothesis.

Most worryingly, this confusion of religion and science does not come from science journalists; it comes directly from the practitioners in my field. Many of my colleagues have become careless in separating belief from fact. They speak of existence without stopping to ask what it means for something to exist in the first place. They confuse postulates with conclusions and mathematics with reality. They don’t know what it means to explain something in scientific terms, and they no longer shy away from hypotheses that are untestable even in principle.
She is right, but with this attitude, she is not going to get tenure anywhere good.

Deepak Chopra wrote a letter to NY Times in response to Sean M. Carroll's op-ed. He mixes quantum mechanics and consciousness in a way that drives physicists nuts. They regard him as a mystic crackpot whose ideas should be classified as religion. But he is not really as bad as Carroll. It would be easier to test Chopra's ideas than Carroll's many-worlds nonsense.

Carroll is an example of a physicist confusing religion and science.

Wednesday, September 18, 2019

The politics of quantum mechanics

Lubos Motl writes:
You know, for years, many people who were discussing this blog were asking: What do axioms of quantum mechanics have to do with Motl's being right-wing? And the answer was "virtually nothing", of course. Those things really were assumed to be uncorrelated and it was largely the case and it surely should be the case. But it is no longer the case. The whole political machinery of raw power – at least one side of it – is now being abused to push physics in a certain direction.You know, for years, many people who were discussing this blog were asking: What do axioms of quantum mechanics have to do with Motl's being right-wing? And the answer was "virtually nothing", of course. Those things really were assumed to be uncorrelated and it was largely the case and it surely should be the case. But it is no longer the case. The whole political machinery of raw power – at least one side of it – is now being abused to push physics in a certain direction.
Maybe Motl is on to something.

Sean M. Carroll has written a preposterous book advocating the many-worlds version of quantum mechanics. It is being widely promoted in the left-wing news media, while right-wing sources either ignore or trash it. Is that a coincidence?

There is something about the left-winger that wants to believe in parallel universes. Carroll also says:
If the universe is infinitely big, and it looks the same everywhere, that guarantees that infinite copies of something exactly like you exist out there. Does that bother me? No.
I think that this is a left-wing fantasy. Do right-wingers about such unobservable egalitarianism? I doubt it.

Sunday, September 8, 2019

Carroll promotes his dopey new quantum book

Physicist Sean M. Carroll has a NY Times op-ed today promoting his stupid new book.
“I think I can safely say that nobody really understands quantum mechanics,” observed the physicist and Nobel laureate Richard Feynman. ...

What’s surprising is that physicists seem to be O.K. with not understanding the most important theory they have.
No, that is ridiculous.

I assume that Feynman meant that it is hard to relate quantum objects to classical objects with a more intuitive understanding. Physicists grappled with the theory in the 1920s, and by 1935 everyone had a good understanding of it.
The reality is exactly backward. Few modern physics departments have researchers working to understand the foundations of quantum theory.
That is because the foundations were well-understood 90 years ago.
In the 1950s the physicist David Bohm, egged on by Einstein, proposed an ingenious way of augmenting traditional quantum theory in order to solve the measurement problem. ... Around the same time, a graduate student named Hugh Everett invented the “many-worlds” theory, another attempt to solve the measurement problem, only to be ridiculed by Bohr’s defenders.
They deserved to be ridiculed, but their theories did nothing towards solving the measurement problem, are philosophically absurd, and have no empirical support.
The current generation of philosophers of physics takes quantum mechanics very seriously, and they have done crucially important work in bringing conceptual clarity to the field.
Who? I do not think that there is any living philosopher who has shed any light on the subject.
It’s hard to make progress when the data just keep confirming the theories we have, rather than pointing toward new ones.

The problem is that, despite the success of our current theories at fitting the data, they can’t be the final answer, because they are internally inconsistent.
This must sound crazy to an outsider. Physicists have perfectly good theories that explain all the data well, and yet Carroll writes books on why the theories are no good.

The theories are just fine. Carroll's philosophical prejudices are what is wrong.

Carroll does not say what would discredit himself -- he is a big believer in many-worlds theory. If he wrote an op-ed explaining exactly what he believes about quantum mechanics, everyone would deduce that he is a crackpot.

Philosopher Tim Maudlin also has a popular new essay on quantum mechanics. He is not so disturbed by the measurement problem, or indeterminism, or Schroedinger's cat, but he is tripped up by causality:
What Bell showed that if A and B are governed by local physics — no spooky-action-at-a-distance — then certain sorts of correlations between the behaviours of the systems cannot be predicted or explained by any local physics.
This is only true if "local physics" means a classical theory of local hidden variables. Bell did show that quantum mechanics can be distinguished from those classical theories, but there is still no action-at-a-distance.

Update: Lumo trashes Carroll's article. Woit traces an extremely misleading claim about a physics journal editorial policy. The journal just said that it is a physics journals, and articles have to have some physics in them. Philosophy articles could be published elsewhere.

Saturday, September 7, 2019

Deriving free will from singularities

William Tomos Edwards writes in Quillette to defend free will:
[Biologist Jerry] Coyne dismisses the relevance of quantum phenomena here. While it’s true that there is no conclusive evidence for non-trivial quantum effects in the brain, it is an area of ongoing research with promising avenues, and the observer effect heavily implies a connection. Coyne correctly points out that the fundamental randomness at the quantum level does not grant libertarian free will. Libertarian free will implies that humans produce output from a process that is neither random nor deterministic. What process could fit the bill?
No, they are both wrong. Libertarian free will certainly does imply that human produce output that is not predictable by others, and hence random. That is the definition of randomness.

Quantum randomness is not some other kind of randomness. There is only one kind of randomness.

Then Edwards goes off the rails:
Well, if the human decision-making process recruits one or more irremovable singularities, and achieves fundamentally unpredictable output from those, I would consider that a sufficient approximation to libertarian free will. Furthermore, a singularity could be a good approximation to an “agent.” Singularities do occur in nature, at the center of every black hole, and quite possibly at the beginning of the universe, and quantum phenomena leave plenty of room open for them. ...

The concept of a singularity becomes important once again here because if you can access some kind of instantaneous infinity and your options are fundamentally, non-trivially infinite, then it would seem you have escaped compatibilism and achieved a more profound freedom.
Now he is just trolling us. There are no singularities or infinities in nature. You can think of the center of a black hole that way, but it is not observable, so no one will ever know. There certainly aren't any black holes in your brain.

Coyne replies here, but quantum mechanics is out of his expertise.