Audio explanation of quantum computers

SciAm is hosting the Tech Talker on Detangling Quantum Computers:

For example, it is really hard for normal computers to find factors of prime numbers. [at 1:30]

It is just as hard for quantum computers to find factors of prime numbers. Primes do not have any nontrivial factors. Okay, I am nitpicking. I have heard this error many times.

At 3'00 to 3'30, it explains superposition as one observer measuring an electron as spin up at the same time another measures spin down.

No, that is impossible.

I am not sure it is even useful to talk about an electron being in a superposition of spin states. It always has a spin in some direction. Only if you force it into another direction does it look like a possibility of up or down in that direction.

And there is no mention of the fact that quantum computers are completely hypothetical fantasies, like time travel machines.

On a recent Slate podcast, I heard:

The word quantum is Latin for: (a) uncertainty (b) parallel (c) natural (d) what amount

The correct answer is (d). Other wrong answers might be "small" or "discrete"

Philosopher a fan of crackpot evolutionist

Biologist-philosopher Massimo Pigliucci did not like me trashing modern philosophers as having no worthwhile influence on physics, and wrote:

You have obviously read no philosophy of science whatsoever.

He did not like my reaction to this comment:

As for philosophical accomplishments, I can name two:
1) The Scientific Method — Science was not a separate field until recently; not until the 19th or 20th century, I believe. Galileo, Newton, Copernicus, Kepler, along with all the other ‘scientific minds’ of the Scientific Revolution, were natural philosophers. Science is the child of philosophy.
2) The Sex/Gender Distinction — Unless I am mistaken, it is a firmly held belief in various fields (feminism, anthropology, psychology(?), etc.), and a common belief among lay men, that there is a distinction between one’s reproductive role (sex) and the cultural, behavioral norms they must follow qua sexed person (gender). This distinction was introduced by Simone De Beauvoir, an Existentialist philosopher. This seems like a big accomplishment for philosophy.

I did suspect that this comment was a joke. Sure, the scientific method was big, but that goes back millennia. But the sex/gender distinction? Really? Is that the best philosophy has done in 300 years? The distinction is of interest to a few trannies, but not much anyone else.

Pigliucci is a big fan of Stephen Jay Gould, and wrote a 1998 5-star review of Gould's most famous book, The Mismeasure of Man:

Steven J. Gould is most famous among the general public for his collections of essays from his long Natural History series, "This View of Life". But the best of Gould's writing is perhaps to be found in his single-theme books. And The Mismeasure of Man is arguably the finest among them. The volume is about the long history of the search for scientific justification of racism, and the many faux pas that science has committed when it comes to the study of human intelligence. ...

He illustrates this with an array of definitely intelligent people whose brain sizes covered almost the whole gamut displayed by non-pathological individuals. However, this is indeed one of the troublesome aspects of this book and, I dare say, of Gould's writing in general. He dismisses contrary evidence or arguments so fast that one gets the impression of seeing a magician performing a trick. One cannot avoid the feeling of having being duped by the quickness of the magician's movement, instead of having observed a genuine phenomenon. In this particular instance, I can vouch for Gould as a biologist, but I'm not so sure that the general public is willing to trust him on his word. After having dismissed both craniometry and the aberrant work of Cesare Lombroso on the anthropological stigmata of criminals, Gould moves on to his main target: IQ and intelligence testing. ...

That is, the scores on each test are correlated to each other, because they all reflect one underlying quantity, which Spearman named "g", or general intelligence. Spearman therefore provided one of the two pillars of the eugenic movement: there seemed indeed to be one way to rank individuals by their intelligence with the use of one number: this was the score on the g-factor, instead of the score on any of the available IQ tests. Burt's major achievement was a supposed confirmation of the second fundamental piece of the puzzle eugenic puzzle: his studies of genetically identical twins suggested a high heritability (incorrectly read as a high level of genetic determination) of intelligence. So, not only do individuals differ in intelligence, but this is easy to measure and genetically determined. Environment, and with it education and social welfare, cannot alter the innate difference among individuals, genders, and races. QED Well, not really.

No, this book is crackpot stuff. It has no scientific merit, and is wrong on almost every level. You can read the Wikipedia article for details.

Yes, there is overwhelming evidence that there are innate differences among individuals, and a lot of work on how much can be attributed to genetics and how much to the environment. Very few traits are entirely genetic or environmental. This stuff is not particularly controversial, except for Gould fans.

Pigliucci posts a lot of good essays and interviews, and of course he is on the warpath against pseudoscience and creationism. But he is just another philosopher of science with a warped idea of science.

Against quantum realism

Lubos Motl writes:

All the major "realist" attempts to reform the foundations of quantum mechanics – de Broglie-Bohmian mechanics, Ghirardi-Rimini-Weber-like collapse theories, and Everett-style many worlds – are known to suffer from serious diseases. To a large extent, "realism" itself is the problem.

I am still willing to admit that there is no truly "rock-solid proof" of the statement that "there cannot be any realist reinterpretation or 'improvement' of quantum mechanics".

The quest for "realism" in physics is an Einsteinian disease, and led me to write my book on the subject.

We have 80 years of theoretical and experimental evidence, all pointing to the supposedly-realist models of quantum mechanics being wrong. Isn't that enuf?

A Nature article reports:

The bizarre behaviour of the quantum world — with objects existing in two places simultaneously and light behaving as either waves or particles — could result from interactions between many 'parallel' everyday worlds, a new theory suggests. ...

Charles Sebens, a philosopher of physics at the University of Michigan in Ann Arbor, says he is excited about the new approach. He has independently developed similar ideas, to which he has given the paradoxical name of Newtonian quantum mechanics. ...

The next step for the team will be to come up with ways in which their idea can be tested. If the many-interacting-worlds approach is true, it will probably predict small differences from quantum theory, Wiseman says.

This is the game plan. Refuse to accept 1930 physics. Pretend that the world is more like your Newtonian intuitions. Except add some bizarre parallel universes or other nonsense that would be stranger and more non-intuitive than quantum mechanics. Find some way to test it in order to disprove quantum mechanics. Then discover that quantum mechanics still works, just like in 1930. This story has played out a thousand times. Reporting this is like reporting someone's idea for a perpetual motion machine.

It is bizarre that these models are even called realist. Bohmian mechanics supposedly tells you where the electron is, but then requires you to believe that the electron has a sort of guardian angel that has a magical and nonlocal influence on it. The many-worlds requires vast parallel universes that can never be observed.

Webster's defines realism:

1: concern for fact or reality and rejection of the impractical and visionary
2a : a doctrine that universals exist outside the mind; specifically : the conception that an abstract term names an independent and unitary reality
b : a theory that objects of sense perception or cognition exist independently of the mind — compare nominalism
3: the theory or practice of fidelity in art and literature to nature or to real life and to accurate representation without idealization

I guess the idea is that the Copenhagen interpretation of quantum mechanics makes predictions based on our knowledge of the system, and is therefore in the mind. A theory that posits unobservable ghosts would be outside the mind, and therefore realist.

This is backwards. Realism, to me, means accepting what is demonstrably observed, and not living in some fantasy world of unobservables.

So I say that quantum mechanics is realist because it is based on observables and verifiable predictions. Everyone else says that quantum mechanics is an inadequate theory because it is not realist, and it needs to be made realist by hypothesizing unobservable and magical hidden variables or pilot waves or parallel universes.

I can't blamed de Broglie for having some of these ideas in 1923. They were intensely debated in the late 1920s, and thought to be settled then. But it appears that no amount of evidence will convince the Einsteinian physicists who insist that there is a missing ingredient to quantum mechanics that is going to make it realist.

Sean M. Carroll is one who believes that quantum mechanics is missing realism:

But despite its triumphs, quantum mechanics remains somewhat mysterious. Physicists are completely confident in how they use quantum mechanics -- they can build theories, make predictions, test against experiments, and there is never any ambiguity along the way. And nevertheless, we're not completely sure we know what quantum mechanics really is. There is a respectable field of intellectual endeavor, occupying the time of a substantial number of talented scientists and philosophers, that goes under the name of "interpretations of quantum mechanics." A century ago, there was no such field as "interpretations of classical mechanics" -- classical mechanics is perfectly straightforward to interpret. We're still not sure what is the best way to think and talk about quantum mechanics.

This interpretational anxiety stems from the single basic difference between quantum mechanics and classical mechanics, which is both simple and world-shattering in its implications:

According to quantum mechanics, what we can observe about the world is only a tiny subset of what actually exists.

Attempts at explaining this principle often water it down beyond recognition. "It's like that friend of yours who has such a nice smile, except when you try to take his picture it always disappears." Quantum mechanics is a lot more profound than that. ...

Most modern physicists deal with the problems of interpreting quantum mechanics through the age-old strategy of "denial." ...

At some point, however, we need to face the music.

For him, facing the music means believing in unobservable parallel universes.

The idea that we can only observe a tiny subset of reality is just a mystic belief. Or religious. Jesus said, "My kingdom is not of this world." John 18:36. Maybe so, but physics can only deal with what is of this world.

DNS troubles

This blog was down for a couple of days, because of technical server issues. It should be back up when you read this.

Paradigm shift book is still highly cited

Nature magazine has published the Google Scholar top-100 cited list, and near the top is the 1962 philosophy book The Structure of Scientific Revolutions. It popularized the paradigm shift.

This book dominated modern philosophy of science, but it is garbage. Its main arguments are to deny that science makes progress toward truth, deny that new scientific theories are adopted from quantitative evidence, and deny that scientists are rational.

Philosophers and other anti-science academics love this book because it undermines the validity of science. Science crackpots also love this book also, because it presents science as driven by fads. Instead of arguing that their theories are superior in some way, they can just gripe that they are out of fashion.

MIT debate on multiverse

A couple of MIT physics professors debated whether we live in the multiverse:

Arguing in favor was Max Tegmark, a cosmologist at MIT. His MIT colleague, Frank Wilczek, (winner of the Nobel for his work on the strong force) took the opposing position. ...

And then there's the many-worlds interpretation, in which the wavefunction keeps working, but reality breaks, or at least fragments a bit. In this view, there are particles in every location the wavefunction predicts we'll find them. It's just that those locations end up in different universes once the measurement happens. So, as soon as someone makes a measurement, they split the Universe into multiple universes, each with the particle in a different location specified by the wavefunction. ...

Wilczek was a bit more detailed in his criticisms. He's perfectly happy to accept the wavefunction's existence, but feels that "many worlds is metaphysical baggage added on." His main issue is that all the worlds but one aren't accessible to our experience, and therefore can't be explored scientifically. "I am very worried about ascribing full credence to something other than reality," Wilczek said.

Tegmark for his part, thought that was a very narrow view. "This has less to do with QM than the way we perceive reality," he said, later adding, "it's partly 'what's real is what we can observe,' which seems like an ostrich with its head in the sand." But scientifically, Tegmark said that "If Schroedinger's equation applies to every system, no matter how large, we should have many worlds."...

If inflation is right—and most physicists think it is—then the Universe we see is only a small fraction of the whole. And, if you could somehow go past the observable universe, you'd come to a region where inflation is an ongoing process, rapidly expanding space and ultimately creating additional universes.

"If space is infinite, and the odds of being you is not zero—which it's not, since you exist—then you must exist in other places," Tegmark said. "Maybe you'll first find a Shmioneer Works, but if you keep looking, you'll find another [you]." And this weirdness is a necessary outcome of a theory that most physicists agree on. So, in Tegmark's view, you can't dismiss the many worlds interpretation just because it's weird.

The reason for rejecting the multiverse is not that it is weird. It is no weirder than a lot of religious beliefs that people have.

The reasons for rejecting the multiverse are that (1) there is no evidence for it, and no prospects for getting any; (2) it does not solve any theoretical problems; and (3) it is methodologically incoherent, as it destroys the meaning of the Born rule.

If inflation is true, then it is reasonable to say that part of the universe is outside our observable horizon, and hence outside our possible knowledge. The scientific approach would be to acknowledge that there might be something out there, but leave it at that. To say that there are infinitely many copies of ourselves out there is strange and unscientific.

Tegmark is trying to trick you into one of the various paradoxes about infinity, but he has admitted that one of these paradoxes has driven him to conclude that no infinities occur in nature. So I don't know why he keeps bringing up infinities.

I am glad to see physicists debating the many-worlds MWI because it is a silly idea that cannot hold up under debate. It has become somewhat trendy for physicists to announce that they believe in it, but it is stupid on every level -- philosophically, mathematically, and physically.

Black holes in the movies

Dennis Overbye gripes about a new movie in the NY Times:

But the movie doesn’t deserve any prizes for its drive-by muddling of Dr. Hawking’s scientific work, leaving viewers in the dark about exactly why he is so famous. Instead of showing how he undermined traditional notions of space and time, it panders to religious sensibilities about what his work does or does not say about the existence of God, which in fact is very little. ...

But when it came to science, I couldn’t help gnashing my teeth after all. Forget for a moment that early in the story the characters are sitting in a seminar in London talking about black holes, the bottomless gravitational abysses from which not even light can escape, years before that term had been coined. Sadly, a few anachronisms are probably inevitable in a popular account of such an arcane field as astrophysics.

It gets worse, though. Skip a few scenes and years ahead. Dr. Hawking, getting ready for bed, is staring at glowing coals in the fireplace and has a vision of black holes fizzing and leaking heat.

The next thing we know he is telling an audience in an Oxford lecture hall that black holes, contrary to legend and previous theory, are not forever, but will leak particles, shrink and eventually explode, before a crank moderator declares the session over, calling the notion “rubbish.”

The prediction of Hawking radiation, as it is called, is his greatest achievement, the one he is most likely to get a Nobel Prize for. But it didn’t happen with a moment of inspiration staring at a fireplace. And in telling the story this way, the producers have cheated themselves out of what was arguably the most dramatic moment in his scientific career. ...

His discovery has turned out to be a big, big deal, because it implies, among other things, that three-dimensional space is an illusion. Do we live in a hologram, like the picture on a credit card? Or the Matrix?

None of this, alas, is in the movie. That is more than bad history.

Bad history, but I am sure that it would be bad physics either way. No one has shown that 3D space is an illusion. Hawking radiation from black holes has not been observed, and probably won't be. And he won't get that Nobel prize. (Possibly he might get some credit from some analogous radiation that is not from black holes, but I doubt it.) No we do not live in a hologram just because some funny stuff happens on the event horizon of a black hole.

Meanwhile, Sean M. Carroll raves about a new movie:

I haven’t seen it yet myself, nor do I know any secret scoop, but there’s good reason to believe that this film will have some of the most realistic physics of any recent blockbuster we’ve seen. ...

Kip recognized that a wormhole was what was called for, but also realized that any form of faster-than-light travel had the possibility of leading to travel backwards in time. Thus was the entire field of wormhole time travel born. ...

I know that Kip has been very closely involved with the script as the film has developed, and he’s done his darnedest to make sure the science is right, or at least plausible. (We don’t actually whether wormholes are allowed by the laws of physics, but we don’t know that they’re not allowed.) ...

And that’s not all! Kip has a book coming out on the science behind the movie, which I’m sure will be fantastic. And there is also a documentary on “The Science of Interstellar” that will be shown on TV, in which I play a tiny part.

I should reserve judgment until I see the movie. It will probably be entertaining. But if the plot uses wormholes for Earthlings to escape global warming and colonize another planet, then I would not call it realistic physics.

Update: Interstellar has some great reviews, but the Bad Astronomer hated the silly and nonsensical physics plot (relativity, black hole, wormhole).