Quantum Foundations of a Classical Universe

Greetings from sunny (for the moment) Yorktown Heights, NY, home of IBM’s Watson Research Center. I’m behind on respectable blogging (although it’s been nice to see some substantive conversation on the last couple of comment threads), and I’m at a conference all week here, so that situation is unlikely to change dramatically in the next few days.

But the conference should be great — a small workshop, Quantum Foundations of a Classical Universe. We’re going to be arguing about how we’re supposed to connect wave functions and quantum observables to the everyday world of space and stuff. I will mostly be paying attention to the proceedings, but I might occasionally interject a tweet if something interesting/amusing happens. I’m told that some sort of proceedings will eventually be put online.

Update: Trying something new here. I’ve been tweeting about the workshop under the hashtag #quantumfoundations. So here I am using Storify to collect those tweets, making a quasi-live-blog on the cheap. Let’s see if it works.

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26 Responses to Quantum Foundations of a Classical Universe

  1. Walker Guthrie says:

    If your talking about wave function and would like to see a nice classical model, you my find my short video interesting. It appears to be a variation of Euler’ contained column theory which produces cascading waves like the probability solutions to the wave equation.


  2. dmck says:

    Third paragraph of the meeting description: how is WHAT classically connected?

  3. Stewart says:

    A conference on issues that have not progressed in decades, with overpaid professors, all organized in order for everyone involved to feel important and to feel like they are contributing to society.

  4. Stewart says:

    Oh wait a minute. Some of those talks actually look interesting. Please disregard my comment above. I take it all back. I apologize.

  5. Quantum Foundations of a Classical Universe

    Of course a Classical Universe, up to the 20th century, was quite understandable. The present beliefs concerning the makeup of the universe is not quite so simple, via dark matter, dark energy, Inflation, Warped space, Quantum theory, etc. Regardless of how the universe is made up in fact, it would have a quantum foundation to it — of course. Would this foundation be related to Quantum Theory and Mechanics?

    I would bet two six packs of Guinness against most of today’s quantum theory but probably could not collect in at least 20 years. My intellectual thirst will remain unquenched until a simple, totally logical quantum theory is realized 🙂 Most believe this is impossible.

  6. Elbi Gilgen says:

    Adrian Kent was pretty rude in his latest paper…. are you going to ask him to take it Outside?

  7. Michael K Murray says:


    Better take it up with IBM and the John Templeton Foundation from the look of the conference description

    Financial and logistical support has been generously provided by IBM, and by the John Templeton Foundation through grant number 21484.

  8. JW Mason says:

    Elbi Gilgen-

    I assume you mean this: http://arxiv-web3.library.cornell.edu/pdf/1408.1944v1.pdf

    I also would like to see Sean’s response. Kent’s arguments seem convincing to me: Sean’s version of many worlds assumes that the hard problem has already been solved, and that we already have an objective basis for dividing the wave function into distinct branches.

  9. B^2 says:

    “Let’s discuss consciousness while waiting for stragglers to arrive. That way they won’t miss anything.” Did you talk about the fact that a human being uses 100W of power to produce consciousness ? I think the brain itself requires less energy than that but I’m including the body because it is needed to support the brain. I think Watson must have been posting on the last few threads. Alright let me think about these interesting questions from the beginning:

    When can a quantum state, pure or mixed, be said to be classical? Can this definition be made statically, or are dynamical considerations needed?

    Maybe we should just discuss quantum computing instead?

  10. Jiggawatt says:

    @B^2 we first should discuss degeneracy in quantum mechanics. For instance the number of times you used the word “think” (3 times) in the previous post would be an example of getting the same measurable eigenvalue from a dictionary. If you used a thesaurus it would act as another measurement to further specify the state of your thoughts.

    There are certain observables in quantum mechanics that do commute like the energy and momentum of a free particle. If two observables (energy, momentum, spin, position and beer) commute then there is no uncertainty in our measurements and we can measure observables together with as much certainty as we want. If we were to measure the momentum observable with greater certainty then our uncertainty in position would increase proportionally since the energy and momentum observables do not commute. It is possible to completely specify the state of a quantum system by using observables that do commute and ignoring the observable combinations that do not commute.

    A mixed state is an ensemble of pure states and I should note that the ensemble interpretation is not the most popular interpretation of quantum mechanics. A pure state is a state that is in a coherent superposition of basis states but one of the possible basis states is found with absolute certainty after a measurement. A mixed state is what we may consider to be classical and a pure state exhibits quantum properties like interference among the basis vectors.

    This is where the Schrodinger’s cat analogy is useful. The atom which is in a superposition of pure states determines if a cat (a large macroscopically cellular ensemble of mixed states) is dead or alive. To say that the cat is dead and alive at the same time is applying a pure state to a mixed state. And Schrodinger was trying to illustrate with this analogy that we should think about pure and mixed states differently. However, the Copenhagen interpretation has perverted this analogy into the cat being in a pure state superposition of dead and alive until a measurement is performed by an outside observer. In a mixed state both outcomes have equal probability so naively we may say that the state of dead and alive is 50/50 instead of a coherent superposition of both dead and alive states at the same time. At any moment the cat is either dead or alive and never dead and alive. However, as time goes on it is more likely that the cat is dead. It is possible to have pure states at larger scales, however, the point Schrodinger was making was that it is indeed stupid to apply a pure state to a mixed state. It would be like saying a cat was dead and alive at the same time which is obviously wrong.

    It is usually thermal noise which turns a pure state into a mixed state. And we should expect that a working quantum computer would be well insulated from noise or be able to maintain a pure states for long periods of time.

  11. B^2 says:


    I’m not sure if you’re right because everyone tells me that the cat is dead and alive at the same time not dead or alive. Would you be able to clarify your arguments using some mathematics? You seem to use the word state a lot perhaps a thesaurus would help you. I hope realize that eigenvector, eigenstate and eigenvalues have characteristic meanings in linear algebra. Also would you be able to explain Ehrenfest’s theorem to me? Would you mind explaining the Bloch vector too? If time and energy do not commute then are you suggesting that time and energy are observables? I thought time was a stubbornly persistent trick .

  12. Avattoir says:

    Jiggawatt – Everything I’ve read on what Schrodinger was up to with his cat thought experiment is consistent with how you’ve put it here; that Schrodinger was NOT with Heisenberg, Bohr’s former student, on ‘Team Bohr’ in the ongoing debate; rather, he came up with the cat idea correspondence with Einstein in the context of supporting ‘Team E’ (E for Einstein). Bohr championed the view that Heisenberg’s Uncertainty Principle meant that one couldn’t “determine” the location of an electron in advance of “measurement”, IOW that act of interfering with the system. Einstein enlisted Schrodinger for the proposition that measurement only DISCOVERED the objective position of the electron at a point in time, which would still have been it’s position at that point in time regardless the act of measurement. Bohr was declared the victor over Einstein by positing one could accurately forecast the probability of the electron being located in various positions.

  13. Kevin Henderson says:

    I noticed the conference is partly sponsored by the John Templeton Foundation. How, Who, and Why would be sponsored by them?

  14. Richard says:

    So I’m wondering what the outcome of the discussion was…Is it ontic or epistemic?

  15. John Barrett says:

    Why do I always get the feeling that I am the only person that really doesn’t see anything wrong with the Copenhagen Interpretation? I have always thought that it was more likely that the real problem lied with the Schrodinger Cat thought experiment. It may be that just the dead cat exist and doesn’t exist at the same time relative to the alive cat. Why does it have to be only dead and alive relative to the experimenter? When a particle decays it decayed and didn’t decay at the same time relative to what? The cat itself may only actually be in a state of superposition relative to some particle from the decay process. Then it may be just the particle looking around thinking, man that is one strange cat.

  16. Jiggawatt says:

    I thought this was an interesting tweet:

    “People admit there is no universal definition of “quantum fluctuations,” and are reluctant to propose any.”

    I was randomly clicking buttons when I found this short blurb from a documentary on freak waves . Is the amplitude of the wave related to the energy and entropy or is it a probability for a set of possible energy eigenvalues? I think in this example it is related to energy and entropy because the energy is randomly concentrated in one place, but luckily energy in this example is still conserved. How would you describe the ocean using coordinate patches?

  17. Jiggawatt says:

    Avattoir thanks for your reply. What is your favorite interpretation of quantum mechanics?

  18. Jiggawatt says:

    @B^2 I am a little busy writing soon to be rejected grant proposals. I would love to derive some equations for pure and mixed states. Give me a few days to find all of my notes and I’ll go through the motions of the equations with you.

  19. B^2 says:

    John Barrett ignore the down votes because what matters is that you are thinking about quantum mechanics. What is the cat’s body temperature?

    Kevin Anderson you forgot to mention that the Templeton prize is always to exceed the monetary value of the Nobel prize. I think the Templeton foundation is trolling the Nobel committee to pay the Nobel laureates more money. What I never understood is why a faith based foundation would want to support science with research grants. I think John Templeton may have understood that your return on investment is greater when you invest in a basket of equities. You might even say that an index mutual fund is an ensemble of stocks. Funding scientists without meddling in their work is a fantastic ethos because if a stock broker cannot pick hot stocks then how do we know what research investments will be important?

    Jiggawatt, my old nemesis, are you subtly implying that the cosmic microwave background is a thermal reservoir like the Earth’s ocean? How would stable states of bosons lead to an abundance of matter over anti-matter? It was a dark energy inflationary explosion of space-time and matter which created the universe. If there were a steady rate of anti-matter and matter coming into existence then every detector would be able to register a low level background radiation. We all know that the background radiation comes from the potassium atoms in bananas. There are some cosmic ray sources too, however, those gamma ray sources are definitely not the gamma rays produce when matter and anti-matter annihilate each other.

  20. Jiggawatt says:

    B^2 you’re right it was a dark energy inflationary explosion of matter in the empty background dependent minkowski space. Fred Hoyle, the father of the steady state theory, snarkily called George Gamow’s idea on the creation of the universe the big bang and the name stuck. It is similar to Schrodinger using his cat example and then other theorists (such as Bohr) applying it erroneously to the Copenhagen interpretation. Unfortunately, I was not an English professor , but I believe that is called irony.

    You’re right if we assumed that a CMB with no temperature variation was the state of maximum entropy then we would be able to calculate the amount of energy converted into matter. I’m not sure that energy being converted into mass has ever been observed experimentally though. If energy can be converted into mass than the energy variation in the CMB heat map seen here may help us to understand the creation of the universe. Although I am not sure if we have a similar heat map of the neutrino distribution of the universe since they are hard to detect.

  21. I enjoyed your tweets from the meeting, thank you. It’ interesting having Aaronson name and consciousness mentioned. I wonder if his office at MIT is near Max Tegmarks?

  22. Richard says:

    Wow, looks like this thread got attacked by a gang of haters.

    Go ahead, fellows, do your worst.

  23. Jesper Both Pedersen says:

    Great post and really fascinating. Thanks, Sean.

  24. Elbi Gilgen says:

    This system of hiding comments with too many thumbs down is really good. It directs one’s attention to the posts that are worth reading, ie the ones that get a lot of thumbs down.

  25. kashyap vasavada says: