Wednesday, April 27, 2016

Questioning quantum supremacy

KWRegan writes:
Gil Kalai is a popularizer of mathematics as well as a great researcher. His blog has some entries on Polymath projects going back to the start of this year. He has just contributed an article to the May AMS Notices titled, “The Quantum Computer Puzzle.” ...

Quantum supremacy has a stronger meaning than saying that nature is fundamentally quantum: it means that nature operates in concrete ways that cannot be emulated by non-quantum models. If factoring is not in BPP — let alone randomized classical quadratic time — then nature can do something that our classical complexity models need incomparably longer computations to achieve.

Kalai says:
Quantum computers are hypothetical devices, based on quantum physics, which would enable us to perform certain computations hundreds of orders of magnitude faster than digital computers. This feature is coined “quantum supremacy”, and one aspect or another of such quantum computational supremacy might be seen by experiments in the near future: by implementing quantum error-correction or by systems of noninteracting bosons or by exotic new phases of matter called anyons or by quantum annealing, or in various other ways. ...

A main reason for concern regarding the feasibility of quantum computers is that quantum systems are inherently noisy. We will describe an optimistic hypothesis regarding quantum noise that will allow quantum computing and a pessimistic hypothesis that won’t. ...

Are quantum computers feasible? Is quantum supremacy possible? My expectation is that the pessimistic hypothesis will prevail, leading to a negative answer.
I agree with Kalai that the quantum computer is the perpetual motion machine of the 21st century.

Monday, April 25, 2016

European Quantum Manifesto

SciAm reports:
The European Commission has quietly announced plans to launch a €1-billion (US$1.13 billion) project to boost a raft of quantum technologies—from secure communication networks to ultra-precise gravity sensors and clocks.

The initiative, to launch in 2018, will be similar in size, timescale and ambition to two existing European flagships, the decade-long Graphene Flagship and the Human Brain Project, although the exact format has yet to be decided, Nathalie Vandystadt, a commission spokesperson, toldNature. Funding will come from a mixture of sources, including the commission, as well as other European and national funders, she added.

The commission is likely to have a “substantial role” in funding the flagship, says Tommaso Calarco, who leads the Integrated Quantum Science and Technology centre at the Universities of Ulm and Stuttgart in Germany. He co-authored a blueprint behind the initiative, which was published in March, called the Quantum Manifesto. Countries around the world are investing in these technologies, says Calarco. Without such an initiative, Europe risks becoming a second-tier player, he says. “The time is really now or never.” ...

High-profile US companies are already investing in quantum computing, and Chinese scientists are nearing the completion of a 2,000-kilometre long quantum-communication link — the longest in the world — to send information securely between Beijing and Shanghai.

In Europe, the flagship is expected to fuel the development of such technologies, which the commission calls part of a “second quantum revolution” (the first being the unearthing of the rules of the quantum realm, which led to the invention of equipment such as lasers and transistors).
No, there is no practical utility to quantum communication or quantum computing.

Scott Aaronson and others comment on Candian PM Trudeau's description of quantum computing.

Here is my own attempt at a brief 35-second explanation:
Quantum mechanics is a system for tracking the potential observations of atoms, and other phenomena on that scale. In particular it allows calculating probabilities of multiple possibilities, even tho single outcomes are observed.

A quantum computer is a conjectural machine to do computations from interpreting those multiple possibilities as separate realities that can each contribute to what appears to be an almost-magic parallel computation. Despite almost a billion dollars in investment, no such speedups have been achieved.

Thursday, April 21, 2016

Two Dogmas of Empiricism

Modern philosophy of science is mainly characterized by its denial of truth. Philosophers are always arguing that everything is subjective, or that math has no foundation, or that the scientific method is invalid, or that philosophical musings are just as good as experimental results. They just had a conference devoted to non-empirical physics, whatever that is.

A core anti-truth document is the 1951 essay, Two Dogmas of Empiricism, by Harvard philosopher and logician W. Quine.

The essay is widely praised, and even "regarded as the most important in all of twentieth-century philosophy".

The title says "two dogmas", but the essay says that they are the same. The dogma is that empirical knowledge can be distinguished from other kinds.

He concedes that some knowledge is true by simple logic, without recourse to empirical investigation, like:
(1) No unmarried man is married.
But then he has a giant brain freeze trying to classify this:
(2) No bachelor is married.
This seems to be true by definition and logic, because "bachelor" is synonymous with "unmarried man". But then he complains:
But it is not quite true that the synonyms 'bachelor' and 'unmarried man' are everywhere interchangeable salva veritate. Truths which become false under substitution of 'unmarried man' for 'bachelor' are easily constructed with help of 'bachelor of arts' or 'bachelor's buttons.' Also with help of quotation, thus:
'Bachelor' has less than ten letters.
Therefore he argues that it is impossible to distinguish logical and empirical truths, and also that the whole program of scientific reductionism is invalid.

That's it. The argument is that stupid. Of course there are distinctions between logical and empirical truths, even tho the issues drive philosophers nuts. See my defense of logical positivism.

The English language is not as precise as mathematical logic. There are lots of synonyms in English, but that does not mean that they are substitutable in all contexts. Sometimes you need a little context to understand which meaning of a term is being used. This is a trivial observation. Those who praise this essay are morons. Or they are leftists who are ideologically opposed to objective truths.

Tuesday, April 19, 2016

Politician on quantum computing

A reader pointed out that Canada's dopey leader tried to explain quantum computing:
Justin Trudeau’s appeal may have just found a new dimension.

The Canadian Prime Minister was asked about the deployment of airstrikes against ISIS at a press conference on April 15, but the reporter had inserted a joke about quantum computing beforehand.

Trudeau took the bait, and launched into an explanation of the quantum computer.

“Normal computers work by …” Trudeau said, before he was greeted by an outburst of laughter. “Don’t interrupt me. When you walk out of here, most of you will know more about quantum computing.”

Then he proceeded to give a brief summary of what makes quantum computing different from normal computing.

“Normal computers work…either there’s power going through a wire or not. It’s one or a zero. They’re binary systems,” Trudeau said. “What quantum states allow for is much more complex information to be encoded into a single bit.”

“A regular computer bit is either a one or a zero — on or off — a quantum state can be much more complex than that because, as we know, things can be both particle and wave at the same time, and the uncertainty around quantum states allows us to encode more information into a much smaller computer.”

“Don’t get me going on this or we’ll be here all day,” Trudeau said at the end of his explanation, to cheers from the crowd.
He began a Master's degree in environmental geography before entering politics, so that gives him the ability to talk science, I guess.

No, a quantum computer will never be a smaller computer, even if one is ever built.

It is wishful thinking to say that uncertainty means more information.

Monday, April 18, 2016

PR problem: writing on the evils of Darwinism

Pseudoscience philosophy professor Massimo Pigliucci writes:
What can be done in order to help philosophy out with its PR problem, other than attempting to educate some prominent physicists and perhaps gently nudge toward retirement those senior philosophers who suddenly begin to write about the evils of “Darwinism”?
It is funny how these leftist-atheist-evolutionists think. Philosophers can say that the world is not real, or that there is no free will, or that there are zillions of unobservable parallel universes, or that there is no causality in fundamental science, and he says that is all just good modern enlightened thinking. But if anyone questions any aspect of Darwinism, then he should be purged from the society of respectable philosophers.

Pigliucci admits that philosophers get no respect, but blames it on the ignorance of physicists.

No, the problem with modern philosophers is that they are ignorant of modern science, and they deny that science is progressing towards truth.

Friday, April 15, 2016

Bee on essentials of quantum mechanics

Bee and Lumo are mostly in agreement on what quantum mechanics is about. Rather than nitpick, I emphasize where they are right, and most of the popular explanations are wrong.
Quantization doesn’t necessarily imply discreteness
Common explanations say that everything must be discrete, that the world is made of particles, and that even spacetime must be grainy.

Quantum mechanics says that eigenvalues are observed, and the spectrum can be continuous or discrete. Photons are not really discrete; they are just observed that way when emitted or absorbed by atoms because of the energy spectrum of electron orbitals.

Read my motto. Nature is continuous.

Many of the quantum gravity folks are eager to argue that everything is discrete. The new best-selling Rovelli book concludes that "space is granular, time does not exist, and things are nowhere". No, this is a misrepresentation of quantum mechanics.
There is no spooky action at a distance
People claim that spooky action was proved by Einstein or Bell or quantum computers. Nope.

This recent paper on Bell interpretations says that the conventional view is that Bell experiments prove spooky action at a distance. So does this recent blog post. This conventional view is wrong.
Schrödinger’s cat is dead. Or alive. But not both.
A more interesting question is whether quantum computers can do a super-Turing computation based on qubits being on and off at the same time. I argue that it is impossible. Those who say it must be possible based on quantum mechanics are suffering from an extension of the Schroeding cat fallacy.

Wednesday, April 13, 2016

A theory is not a hunch

The NY Times theory:
Misconception: It’s just a theory.

Actually: Theories are neither hunches nor guesses. They are the crown jewels of science.

One day, it’s Megyn Kelly who has a theory about why Donald J. Trump hates her.

Another day, the newly released trailer for the next Star Wars movie inspires a million theories from fans about who Rey’s parents are.

And on Twitter, someone going by the name of Mothra P.I. has a theory about how cats can assume a new state of matter:
I have a theory, that cats are actually in a liquid state some of the time, as demonstrated here...
— Mothra P.I. (@Hardywolf359) April 2, 2016
In everyday conversation, we tend to use the word “theory” to mean a hunch, an idle speculation, or a crackpot notion.

That’s not what “theory” means to scientists.

“In science, the word theory isn’t applied lightly,” Kenneth R. Miller, a cell biologist at Brown University, said. “It doesn’t mean a hunch or a guess. A theory is a system of explanations that ties together a whole bunch of facts. It not only explains those facts, but predicts what you ought to find from other observations and experiments.”
In my experience, physicists use the word "theory" quite lightly, and call things theories when there is not a shred of evidence.

Scientists use the term just like the general public.

Neither use the word to mean a "hunch". In the above layman examples, a theory is not a hunch.

I might say: I have a theory for how Trump might win the nomination. That means I have some plausible scenario for how it might happen, but not that I necessarily believe it.

I might say: Feynman had a theory that there is only one electron in the universe, going forward and backward in time. Again, this is not a hunch, but a possible way of thinking about matter that might be a consistent alternative.

I might say: I have a theory that Hillary Clinton takes orders from Wall Street bankers. Again, I don't necessarily believe it, but I will be on the lookout for when she acts against the interests of those bankers, to see whether this is a useful model of her policies. It could be a useful model, even if she never talks to bankers.

I might say: Some physicists have a theory that we live in a simulation. This doesn't tie together any facts, or explain facts, or predict anything. It is just a stupid thought experiment.

I might say: Lisa Randall has a theory that dark matter wiped out the dinosaurs. That offers an explanation, but the evidence is so weak that I am not even sure that she believes it herself.

To indicate that something is a crackpot notion, sometimes people use the term "conspiracy theory". For example, someone might say that there is a conspiracy theory that physicists are promoting super-powerful RSA-breaking quantum computers as the inevitable consequence of proven quantum mechanics. I do not really agree with that usage, because it puts the emphasis on the secret agreement to deceive, and there may not be one.

It makes more sense to say that there is a conspiracy theory that the Moon landing was faked. Such fakery would have required a massive secret agreement. It is the conspiracy allegation that makes it a crackpot notion, not saying that it is a theory.
Dr. Miller is one of the few scientists to have explained the nature of theories on a witness stand under oath.

He is a co-author of a high school biology textbook that puts a strong emphasis on the theory of evolution. In 2002, the board of education in Cobb County, Ga., adopted the textbook but also required science teachers to put a warning sticker inside the cover of every copy.

“Evolution is a theory, not a fact, regarding the origin of living things,” the sticker read, in part.

In 2004, several Cobb County parents filed a lawsuit against the county board of education to have the stickers removed. They called Dr. Miller, who testified for about two hours, explaining, among other things, the strength of evidence for the theory of evolution.
What the article does not explain is that appeal threw out the lawsuit, and rejected Miller's supposedly expert testimony. Here is the appeals ruling:
The court did rule that Dr. Kenneth Miller, co-author of Biology, would be permitted to testify for the plaintiffs, but only as a fact witness not as an expert. ...

(15) Dr. Miller testified about what the order describes as "the colloquial or popular understanding of the term [theory]." Does he have any qualifications to testify as an expert on the popular meaning of the word "theory"?
So while Miller did offer an explanation of the meaning of the term "theory", that testimony was explicitly rejected by the trial and appeals courts.

I don't know why evolutionists are so insecure about evolution being a theory, or why they are always lecturing us about a definition. They say we have a misconception, but they are refuted by their own examples.

Evolution is an unbrella term that include various concepts, ranging from the trivially obvious to wild speculation. Apparently the leaders in the field are trying to trick us into accepting all of it by telling us that it is a theory so it must be true.

Tuesday, April 12, 2016

Philosopher of pseudoscience attacks scientists again

Massimo Pigliucci has posted another rant against physicists who disrespect modern philosophers:
It is simply historically incorrect to claim that positivism may underlie the current disagreements between philosophers and physicists, because philosophers have not considered logical positivism a viable notion in philosophy of science at least since the 1960s, following the devastating critiques of people like Quine, Putnam and Kuhn. If physicists still think that positivism commands the field in philosophy then it is the physicists who need to update their notions of where philosophy is. When Weinberg states that “it seems to me unlikely that the positivist attitude will be of much help in the future” he is absolutely right, but no philosopher of science would dispute that — or has done so for a number of decades.
Positivism does underlie the disagreements.

Most scientists are positivists. They may be unfamiliar with philosophical definitions of positivism, but they broadly believe that they are using science to determine truths about the natural world, and positivism (and logical positivism) come closest to their views.

When scientists find out that philosophers rejected all of them in the 1960s, and replaced it with crackpot nonsense, then respect for philosophers disappears.

Pigliucci misrepresents the views of Steve Weinberg (and of the other scientists). Yes, Weinberg has some criticisms of positivism, but he still much more of a positivist than a follower of Quine, Putnam, Kuhn, or the other anti-science philosophers.

Much of academia today has degenerated into such anti-intellectual, anti-truth, anti-progress political nonsense that it is barely worth addressing. Philosophers have join the crackpots.

While Pigliucci trashes Larry Krauss for trying to show why the universe exists (and for trashing a philosopher who reviewed Krauss's book title instead of the book), Scott Aaronson presents his own answer:
My view is that, if we want to make mental peace with the “Why does the universe exist?” question, the key thing we need to do is forget about the universe for a while, and just focus on the meaning of the word “why.” ...

Admittedly, suppose there were a giant red button, somewhere within the universe, that when pushed would cause the entire universe (including the button itself) to blink out of existence. In that case, we could say: the reason why the universe continues to exist is that no one has pushed the button yet. But even then, that still wouldn’t explain why the universe had existed.
This sounds a little like his explanation for why quantum computers ought to be possible. He says that no one has found a giant red button to make them impossible.

Monday, April 11, 2016

Rovelli hits best-seller lists

A physics book has hit the best-seller lists:
Mr. [Carlo] Rovelli has been making some waves of his own. The 59-year-old theoretical physicist published a slim book “Seven Brief Lessons on Physics” in his native Italy in 2014. Since then, the book, which delves into quantum gravity and the heat of black holes, has climbed Europe’s best-seller lists and sold rights in 34 languages.

It joins a small cohort of breakout books in physics. Brian Greene’s “The Elegant Universe,” which introduced string theory to a broader public, was a Pulitzer Prize finalist in 2000, while Stephen Hawking’s classic 1988 “A Brief History of Time” has sold over 10 million copies world-wide. Other works aimed at nonspecialists are on the way. After the gravitational waves announcement in February, Knopf fast-tracked the release date for Janna Levin’s forthcoming book, “Black Hole Blues.” Originally scheduled for August, it will now come out later this month. ...

At just under 100 pages, “Seven Brief Lessons” is what it purports to be: a primer on seven key ideas in modern physics. But it’s also poetic and broadly philosophical, with references to Shakespeare scattered throughout. Its final chapter, the author writes in his introduction, “asks how it is possible to think about our existence in the light of the strange world described by physics.”
I have discussed Rovelli before.

The book is filled with the usually Einstein idolotry, and the obsession with some sort of unified field theory to supersede general relativity and quantum mechanics. This kind of book gives a false idea of what physics is about.

Friday, April 8, 2016

More monster black holes

Conventional wisdom is that the strongest argument against the Standard Model of high-energy physics is the existence of dark matter. There is now very strong astronomy evidence that galaxies are held together by masses that we cannot see. The observable mass cannot account for all the necessary gravitational forces. The missing mass must be some sort of dark matter that is away from the center of the galaxy.

The consensus is that there must be some new invisible particle. Many thousands of physicists are looking for it at the CERN LHC and in exotic detectors.

But maybe there is no missing particle, the Standard Model is right, and the missing mass is in black holes?

NPR reports:
Scientists have discovered a supermassive black hole that may be the biggest ever spotted — and its location in a ho-hum group of galaxies suggests that cosmic monsters like this one might be more common than astronomers previously thought.

The newly discovered black hole is about 17 billion times more massive than our sun. Another black hole is currently listed in the Guinness World Records as the heaviest, because it may be as much as 21 billion solar masses. But the measurement of that black hole was not very precise and it might actually be less massive than the new one, which is described in this week's issue of the journal Nature.

"It has highest confidence of anything I've seen of being the largest black hole," says Karl Gebhardt, an astrophysicist at the University of Texas, Austin and expert on black holes. He was not involved in the study.

Astronomers know only of a few black holes that have reached this mind-boggling size. Garden-variety black holes that form at the end of a star's life are much, much smaller. The recent observation of gravitational waves, for example, detected ripples from the merger of two black holes that were each roughly 30 times the mass of the sun.

And then there are the so-called supermassive black holes that can be found at the center of galaxies, like the one in our own Milky Way. "I hate to call that one puny, but it has only 4 million solar masses, and we found one that is 17 billion solar masses," says Chung-Pei Ma, an astronomer at the University of California, Berkeley who led the research in the Nature study.

What strikes her is that this beast lives in what she called "a cosmic backwater," an average-looking group of galaxies. The only other known black holes that are about this size were found in dense clusters of very large galaxies.

"It's sort of like, you would expect to find skyscrapers at the center of Manhattan, but this one is more like finding a very, very tall building somewhere in a small town in the U.S. where you would not expect to see something so big," Ma says. "It gives the possibility that these monster black holes are much more common than previously thought."
There are also the medium-sized black holes that LIGO claimed to discover, and I mentioned the possibility that they may account for dark matter.

Black holes form from collapsing stars. So they are all bigger than our Sun. They can get bigger by swallowing up dust, stars, and other black holes. If there are giant monster black holes, then black holes must come in all sizes, from the star up to the monster.

The Wikipedia List of common misconceptions used to say that it was a misconception that black holes can act as cosmic vacuum cleaners. I sometimes objected, pointed to astrophysics papers describing black holes sucking up matter. The consensus was that it was still a misconception, because the black holes do not suck as much as people think. After many corrections, it now says:
Black holes, contrary to their common image, have the same gravitational effects as any other equal mass in their place. They will draw objects nearby towards them, just as any other planetary body does, except at very close distances.[185] If, for example, the Sun were replaced by a black hole of equal mass, the orbits of the planets would be essentially unaffected. A black hole can act like a "cosmic vacuum cleaner" and pull a substantial inflow of matter, but only if the star it forms from is already having a similar effect on surrounding matter.[186]
I think that this is wrong. Block holes act as cosmic vacuum cleaners much more than people think.

Black holes get to be big somehow. To get so large, they have to pull in matter at a much greater scale than stars ever do. Stars do not get to be so large.

Black holes date back to Michell and Laplace (1783), Schwarzschild (1916), Chandrasekhar (1931), and Penrose and Hawking (1960s). Didn't it occur to any of these guys that black holes might be essential for galaxy formation, and for stabilizing galaxy rotation? The science fiction writers probably worried about accidentally running into black holes, but didn't anyone else take the possibility that black holes were common and structurally essential to galaxies?

Wednesday, April 6, 2016

Aaronson says Goedel gremlins are dormant

Complexity theorist Scott Aaronson (of MIT, and now Texas-Austin) writes:
We can put the point even more sharply. The Austrian-born mathematician Kurt Gödel taught that, given any mathematical question that hasn’t been answered yet (except for questions that boil down to a finite calculation, such as whether White has a winning move in a chess game), it’s possible that the answer is unprovable from the usual axioms of mathematics. And yet, 85 years after Gödel uncovered this gremlin at the centre of mathematics, the fact is that it’s remained mostly dormant. Gödel’s Incompleteness Theorem rears its head only in specialised situations: ...

It didn’t need to be that way (or, maybe it did, but it’s not obvious why). A priori, Fermat’s Last Theorem, the Poincaré Conjecture, and pretty much every other statement of mathematical interest could have been neither provable nor disprovable: if true, then totally disconnected from all the other interesting truths, an island unto itself, with the only question (a question of taste!) being whether we should add it on as a new axiom. But it didn’t turn out like that.
No, this is not correct. There was never a possibility that Fermat's Last Theorem might be demonstrably independent of the axioms of set theory.

Any counterexample to FLT could be verified by a finite computation. Therefore the only possibilities were that FLT is provably true, true but not provable, and provably false. Any proof that FLT is independent of axioms would also be a proof that it is true about the integers.

While is it true that independence results are exceptional, the continuum hypothesis was certainly a mainstream math problem. It was the first of Hilbert's famous 1900 list of 23 open problems.

Lumo is flattered to be attaked in this essay, and disagrees with comments about the possibility of P=NP.

Aaronson gives the impression that mathematicians are solving the big questions, but his field of complexity became a real field over 40 years ago when everyone realized that P=NP was such an important question. A lot of really smart mathematicians and computer scientists have worked on it, without success.

And he specializes in the subfield of quantum computer complexity, and there is no consensus on whether a quantum computer is even possible.

Friday, April 1, 2016

Looking for the next Einstein

The Economist mag reports:
Next Einstein, the brainchild of Thierry Zomahoun, a Béninois administrator, is an attempt to scale up African science. At the moment, most African scientists work either in isolation or abroad. ...

Next Einstein is an attempt to overcome this fragmentation, by providing a continental congress at which African scientists can meet. The forum has grown out of the African Institute for Mathematical Sciences (AIMS), of which Mr Zomahoun is president. AIMS is a graduate school with branches in Cameroon, Ghana, Tanzania and South Africa, as well as in Senegal. It was founded in 2003 by Neil Turok, a South African who now directs the Perimeter Institute for Theoretical Physics. ...

AIMS concentrates on maths for two reasons. First, being a subject that requires little equipment beyond students’ brains, it is cheap to teach. Second, when Dr Turok was asking fellow African researchers which subjects would be most pertinent to the continental scientific Renaissance he hoped to trigger, most agreed that maths, which is fundamental to the rest of science, was the one to go for. ...

But, as Mr Zomahoun observes, 40% of the world’s children are African. Statistically, therefore, the chances that the next Einstein will come from Africa are good.
This may be a worthy project, but some myths are at work here.

There is a myth that Einstein was a mathematical genius who worked in isolation. Because he had an easy desk job with a lot of free time, he dreamed up some mathematical formulas for how the world ought to work. By some fluke, he was dramatically more intelligent that anyone else. It was not his DNA, because neither his parents nor his kids were very smart.

Probably new Einsteins are being born in Africa, India, and China today, but their genius is untapped. In we only get them laptop computers and internet connection, they would solve problems like global warming and black hole firewalls for us.

Or maybe not.