Thursday, July 10, 2014

Four quantum interpretations defended

Physicist Sean M. Carroll explains a video with four major interpretations of quantum mechanics:
The other participants are David Albert, Sheldon Goldstein, and RĂ¼diger Schack, with the conversation moderated by Brian Greene. The group is not merely a randomly-selected collection of people who know and love quantum mechanics; each participant was carefully chosen to defend a certain favorite version of this most mysterious of physical theories.

David Albert will propound the idea of dynamical collapse theories, such as the Ghirardi-Rimini-Weber (GRW) model. They posit that QM is truly stochastic, with wave functions really “collapsing” at unpredictable times, with a tiny rate that is negligible for individual particles but becomes rapid for macroscopic objects.

Shelly Goldstein will support some version of hidden-variable theories such as Bohmian mechanics. It’s sometimes thought that hidden variables have been ruled out by experimental tests of Bell’s inequalities, but that’s not right; only local hidden variables have been excluded. Non-local hidden variables are still very viable!

RĂ¼diger Schack will be telling us about a relatively new approach called Quantum Bayesianism, or QBism for short. (Don’t love the approach, but the nickname is awesome.) The idea here is that QM is really a theory about our ignorance of the world, similar to what Tom Banks defended here way back when.

My job, of course, will be to defend the honor of the Everett (many-worlds) formulation. I’ve done a lot less serious research on this issue than the other folks, but I will make up for that disadvantage by supporting the theory that is actually true. And coincidentally, by the time we’ve started debating I should have my first official paper on the foundations of QM appear on the arxiv: new work on deriving the Born Rule in Everett with Chip Sebens.
QBism is essentially the same as the Copenhagen interpretation, as promoted by Bohr and Heisenberg around 1930.

GRW has the virtue of being potentially testable, but there is no evidence for it yet. Albert likes it mainly out of a philosophical rejection of positivism, and a belief that GRW somehow better satisfies his beliefs in scientific realism.

The argument for Bohmian mechanics is even more philosophically misguided. It is based on a belief that a theory of nonlocal hidden variables with action-at-a-distance is somehow more scientific that a theory based on observables and experiment. The truth is nearly the opposite.

The many-worlds interpretation adds mysterious unobservable parallel universes, without any scientific payoff.

Quantum mechanics has certain paradoxes, but so do other theories. Relativity has the twin paradox, the reality of the length contraction, and the fact that two events can appear simultaneous to one observer, and not to another.

We do not have reputable physicists running around complaining that relativity does not match their intuitions. Relativity explains the observations, and if it upsets your intuitions, then there is something wrong with your intuitions.

Likewise quantum mechanics matches the observations. For Albert, Carroll, Greene, and Goldstein to complain that it is not scientifically realistic or has some other philosophical defect, they are just showing their stubbornness to accept what was established in 1930.

Lumo explains:
The many worlds "interpretation" doesn't allow us to calculate – or imprint – the generally different probabilities of different outcomes into the "strands" of the film. Even the fans of this religion admit it's the case but some of them say that they are "working on a fix" which is supposed to be enough. (A similarly "modest" fix makes Genesis compatible with all the detailed data about the cosmic microwave background, the DNA, and genetics.)

What they don't realize is that the inability of this theory or "interpretation" to calculate any probabilities isn't just a moderate vice or disadvantage. It is a complete, rigorous proof that this philosophy has nothing to do with the empirical data or science whatever and people who are defending it don't have the slightest clue what they are talking about. Everything that modern science predicts are probabilities or their functions. If your ideas don't predict any probabilities, they don't predict anything at all. They have nothing to do with science.

Moreover, there can't be any fix. There can't even exist a candidate theory that would "extract" the probabilities from something else.
You might think that that an event would be consider more probable if it occurs in most of the parallel universes. However the MWI advocates deny any scientific meaning to counting the universes. Mitchell Porter explains:
If you are a many-worlds theorist, and you want to explain e.g. why QM says event A is twice as probable as event B, the logical explanation is that event A is twice as common as event B, when all the parallel worlds are considered. But Deutsch, Wallace, and now Carroll and Sebens, all reject this approach.

Carroll and Sebens explicitly recommend against trying to count parallel worlds / branches of the wavefunction. For example, on page 15 they speak of “the unrealistic assumption that the number of branches in which a certain outcome occurs is well-defined”.
They simply don't believe in probabilities of outcomes because they believe all outcomes happen. They are denying modern science as we know it, and so are Albert, Greene, and Goldstein.

Lumo writes again:
The people who are trying to revive the objective reality – whether they are assuming Bohmian "real particles plus guiding waves" or various forms of "objective GRW-like collapses" or "many worlds" or any other classical visualization what's going on – are not closer than proper quantum mechanical physicists to genuine science. Instead, they are stubbornly defending the indefensible, a notion (of the objective reality) similar to a tooth fairy that cannot be extracted from our real perception of observations and that may actually be shown to be wrong by a careful enough (but not excessively complicated) analysis of several representative processes in the microscopic world.
I would not phrase it that was, but I do think that belief in those interpretation is rooted in some faulty idea about what science is all about. Instead of accepting that science is about observations, they have a belief that science is about hidden variables instead.


  1. "Martha, have you seen my left sock?"

    "No dear, it was there on the bed a moment ago. I can't see it now, it must have either
    (A.) Returned to the void when its probability wave collapsed.
    (B.) Diverged into another parallel universe where it now exists.
    (C.) Quantum tunneled to China,
    (D.) Dark matter. Dark Energy. Dark whatever.
    or (E.) Our cat must have stolen it and dragged it off to that damn box of his again."

    "oh. found it."

    "Where was it?"

    "I wasn't wearing my glasses, I just couldn't see it".

    "Oh. Damn it honey, all my hard work! Take your glasses back off and pick one of my alternatives before I lose my grant!"

    The above dialogue was presented for the purpose of illustrating modern quantum mechanics if applied to every day life. If you have no idea where something is, or if your detector or test fails to register your subject, please put down the bullshit explanations that pretend actual things are waves on graphs made of numbers that can be hand waved (also known as magic) into and out of existence. The moment you entertain the second hand calculation of probability as the suitable basis of existence and mechanical process, you have left reality far behind you.

    Put on your big boy pants, your glasses, and look at the man behind the god damn curtain the 'experts' are telling you not to pay attention to.

  2. "Instead of accepting that science is about observations"'re still living in 1930. What, Mr. Administrator, your bullshit metrics have determined that my ranking is too low? Well, FU, don't you realize science is about observations. I've been told that quantum mechanics is a mathematical framework for the probabilistic description of noncommutative information. I do not observe any properties of a quantum system or a system at all. The pure state of a classical system defines an objective reality. My complaint is that quantum mechanics is not a physical theory in itself

  3. Mr Administrator: "These are not the results we are looking for. This is not compatible with accepted theory. You are fired"

    Oh I see, Mr. Administrator. Science is just another oligarchy. Have fun in your "All we need is a bigger computer that will solve everything" world of ponzi science. The quantum computer fiasco will follow the same line of comedy that is currently being enacted with the ever bigger energy device called ITER. Just saying "I don't know" is a felony in science. Progress is filling the 50 million electronic landfills called science journals with more trash. See ya.