Off-topic. Greatest snowfall in Jerusalem since 1992. President Peres teaches the Israeli how to keep snowmen from getting cold.
The main result is that there is no consensus on anything. I was actually pleased because I was expecting that there would be a consensus on the wrong answers because that "subdiscipline" of physics is completely screwed; instead, the correct answers were mostly the strongest ones. What did they ask?
Randomness of quantum processes (e.g. decay of nuclei) is:
- 64%: fundamental
- 48%: irreducible
- 9%: only apparent
- 0%: masking a hidden determinism
At any rate, in politics, 64% for "fundamental randomness" would be a solid majority.
Do objects have well-defined properties before measurements?
- 52%: yes, in some cases
- 48%: no
- 9%: undecided
- 3%: always
At any rate, at least roughly 1/2 of the folks has an idea about this important point which is not too bad.
Einstein's view on quantum mechanics is:
- 64%: wrong
- 12%: will be shown wrong
- 12%: we don't know
- 6%: will be shown right
- 0%: is right
Bohr's view on quantum mechanics is:
- 30%: we have to wait
- 27%: wrong
- 21%: correct
- 9%: will be shown right
- 3%: will be shown wrong
A similar split appears when it comes to the measurement problem:
- 39%: solved (now or later) in a different way
- 27%: a pseudoproblem
- 27%: none of the above
- 24%: a severe difficulty threatening QM
- 15%: solved by decoherence
But if you don't care where exactly this boundary lies, you may simply assume that the boundary is somewhere. The microscopic world clearly needs the full quantum mechanics; and for some large objects, the classical logic if not physics becomes acceptable. Bohr et al. knew that so they pretty much postulated this dichotomy – one that we may derive more clearly by decoherence today. If you don't care about the location of the boundary and you're OK with the previous answer "no objective reality prior to the measurement", I think that you must conclude that the measurement problem is a pseudoproblem.
What is the message of the violation of Bell's inequalities?
- 64%: local realism is untenable
- 52%: unperformed experiments have no results
- 36%: some notion of nonlocality
- 12%: action at a distance in the physical world
- 6%: let's not jump the gun, take loopholes seriously
Quantum information is:
- 76%: fresh air in quantum foundations
- 27%: we need to wait
- 6%: useful for applications but of no relevance to foundations
- 6%: neither useful nor relevant
The answer "fresh air" could also be fine in the sense that the quantum-foundation people may be stuck with rubbish and crackpot non-quantum theories trying to "explain" quantum mechanics – so if they do something that isn't wrong, e.g. quantum algorithms, it's a breath of fresh air. But I am not sure whether this was what was meant by the "fresh air".
We must also wait and see to decide whether they will be constructed and whether it will be soon etc. If something will stop us for a very long time, we could also say that they're not "useful". So all answers have some potential to be OK. Much of it depends on the next question:
When will we have a working and useful quantum computer?
- 9%: within 10 years
- 42%: 10-25 years
- 30%: 25-50 years
- 0%: 50-100 years
- 15%: never
Some unusual complaints against the quantum computation were recently discussed by Scott Aaronson: response to Dyakonov, Zork's blogorhythm
Right interpretation of state vectors:
- 27%: epistemic/informational
- 24%: ontic
- 33%: a mix of epistemic and ontic
- 3%: purely statistical as in ensemble interpretation
- 12%: other
I believe that all the people who answer "ontic" really mean that the wave function is conceptually a set of classical degrees of freedom. That's why this answer is just wrong. All other answers may be partly OK. Epistemic/informational is OK as a "negation" of the wrong "ontic" answer". However, "epistemic" could also lead one to believe that there exist other hidden variables not included in the wave function – i.e. that the wave function is an incomplete description. That's wrong as well. The wave function isn't "ontic" in the classical sense but it's as complete – and, in this sense, as close to "ontic" – as you can get. So you could vote for some "mix" or for "other" which means that you're not quite satisfied with any answer that was given.
I chose not to label the "ensemble interpretation" as correct because the ensemble interpretation makes the claim that only the statistics of the huge repetition of the very same experiment may be predicted by quantum mechanics. This is a very "restricted" or "modest" claim about the powers of quantum mechanics and this modesty is actually wrong. Even if I make 1 million completely different experiments, quantum physics may predict things with a great accuracy.
Imagine that you have 1 million different unstable nuclei (OK, I know that there are not this many isotopes: think about molecules if it's a problem for you) with the lifetime of 10 seconds (for each of them). You observe them for 1 second. Quantum mechanics predicts that 905,000 plus minus 1,000 or so nuclei will remain undecayed (it's not exactly 900,000 because the decrease is exponential, not linear). The relatively small error margin is possible despite the fact that no pair of the nuclei consisted of the same species!
So it's just wrong to say that you need to repeat exactly the same experiment many times. If you want to construct a "nearly certain" proposition – e.g. the proposition that the number of undecayed nuclei in the experiment above is between 900,000 and 910,000 – you may combine the probabilistically known propositions in many creative ways. That's why one shouldn't reduce the probabilistic knowledge just to some particular non-probabilistic one. You could think it's a "safe thing to do". However, you implicitly make statements that quantum mechanics can't achieve certain things – even though it can.
The observer is:
- 39%: a complex quantum system
- 21%: should play no fundamental role whatsoever
- 55%: plays a fundamental role in the application of the formalism but plays no distinguished physical role
- 6%: plays a distinct physical role (soul collapses wave function...)
While the observer is clearly just another complex physical system and plays no distinguished physical role (so the third answer is also OK), it may play a role in the application of the formalism. However, in synergy e.g. with the consistent-histories approach, we may attribute the "subjective choices" to the consistent histories themselves (a framework listing the questions) rather than the observer as an object. For this reason, it looks legitimate to me if someone says that the observer plays no fundamental role whatsoever.
The denial of the "complex quantum system" by 61% of the participants is the most shocking feature of the answers here.
Reconstruction of quantum theory:
- 15%: gives useful insights and has/will supersede the interpretation program
- 45%: gives useful insights but we still need an interpretation
- 30%: cannot solve the quantum foundations
- 27%: will lead to a deeper theory than QM
- 12%: don't know
I also think that the very hypothetical strategy of "reconstruction" is a misunderstanding of the scientific method in general. The right wisdom about Nature can't be directly "reconstructed" by any well-defined procedure. In science, one has to formulate hypotheses at the beginning, and then test them. The "guesswork" (which can't be mechanical) is a necessary part of the process; the creativity and ingenuity of the physicists matters exactly because the "guesswork" matters. This is related to various logical arrows: the evolution of the Universe is a consequence of the laws of physics, not vice versa, so to determine the laws of physics from the observations of the evolution is an "inverse problem" that simply can't have a straightforward solution. It has to be "inferred" by Bayesian inference. That's why the answers always depend on some priors, too, although the dependence may become weak enough once a sufficient amount of evidence is collected and processed.
- 0%: consistent histories
- 42%: Copenhagen
- 0%: de Broglie-Bohm pilot wave
- 18%: Everett many worlds/minds
- 24%: information-based
- 0%: modal
- 9%: objective collapse, GRW or Penrose
- 6%: quantum Bayesianism
- 6%: relational quantum mechanics
- 0%: ensemble interpretation
- 0%: transactional interpretation
- 12%: other
- 12%: no preferred one
How often have you switched interpretation?
- 33%: never
- 21%: once
- 21%: several times
- 21%: no preferred interpretation
Does the choice of interpretation depend on philosophical prejudices?
- 58%: a lot
- 27%: a little
- 15%: not at all
Superpositions of macro- different states are:
- 67%: possible in principle
- 36%: will eventually be realized
- 12%: in principle impossible
- 6%: impossible because of collapse theory
In 50 years, conferences on quantum foundations:
- 48%: will still be organized
- 15%: probably no
- 24%: who knows
- 12%: I organize one no matter what
The authors also discuss some correlations between the answers, probably kind of obvious ones... TRF readers voted overwhelmingly "NO", just like I did.