This relates to the discussion where you’ve apparently participated, and I am not sure whether I can say more. I am quite content with the prediction of the theory, and don’t trust much the feeling of need of further verbal explanation here. If I were pressed to say something, I would say that probably the present formalism of quantum theory isn’t particularly well suited for human intuition. After all, I believe we will get better formalism in future, whatever it means.
The feeling that the collapse is needed somehow to mediate the bomb’s interaction with the detector falls to the same category with the belief that light must propagate in some medium, or a feeling that there must be some absolute time. Such intuitions are sometimes correct, more often wrong.
Based on my experience, most of the ordinary physicists don’t think interpretations of QM are a big issue. It isn’t discussed too often, people are content to do the calculations most of the time. Of course, this may be different among the first-rank researchers.
Just to clarify: in that discussion, I claimed that the bomb tester thought-experiment doesn’t pose any principal difficulty for Copenhagen relative to the standard variations on the double-slit experiment, so that might seem to contradict what I write here. What I meant to say there is that the main feature of the bomb-tester, namely the interaction-free measurement, is also featured in a less salient way in these classic though-experiments, so that Copenhagen also makes sense for the bomb tester if you accept that it makes sense at all.
But if I may ask, how would you reply to the following statement? “Consider the case when we have a dud bomb, and a case when we have a working bomb that doesn’t explode. There is an observable difference between what the detector shows in these outcomes, so replacing the dud bomb with a working one changed the system in a measurable way. We call this change—whatever exactly it might be—collapse.”
Do you believe that this statement would be flawed, or that it is, after all, somehow compatible with the idea that “the collapse is only a mathematical tool”?
Comparing a system with a dud to a system with a working bomb is comparing two different systems, or the same system in two instances with different initial conditions, and thus doesn’t relate to the collapse. I suppose you rather had in mind a statement: “Consider two experiments with a working bomb, and in one the bomb explodes, while in the second it doesn’t. There is an observable difference...”
Well, it is undeniable that there is a difference. The two systems were the same in the beginning and are different in the end. There are three conventional explanations. 1) The systems were different all way long, but in the beginning the difference was invisible for us (hidden parameters). 2) The difference emerged from a non-deterministic process before or during the measurement (collapse). 3) There is no difference, but we see only a portion of reality after the measurement, and a different one in each of the cases (many worlds).
I suggest fourth point of view: Don’t ask in what state the system is, this is meaningless. Ask only what measurement outcomes are possible, given the outcomes we had from the already performed measurements. If you do that, there is no paradox to solve.
There are three conventional explanations. 1) The systems were different all way long, but in the beginning the difference was invisible for us (hidden parameters). 2) The difference emerged from a non-deterministic process before or during the measurement (collapse). [...]
Actually, that’s the distinction I missed! The notion of “collapse” specifically refers to a non-deterministic process, not to a deterministic process that would at some point reveal the previously existing hidden variables.
I suggest fourth point of view: Don’t ask in what state the system is, this is meaningless. Ask only what measurement outcomes are possible, given the outcomes we had from the already performed measurements. If you do that, there is no paradox to solve.
That would basically be the “ensemble interpretation,” right? The theory tells you the probability distribution of outcomes, which you’ll see if you repeat the experiment prepared the same way a bunch of times (frequentism!), and that’s all there is to it. I do have a lot of sympathy for that view, as you might guess from the recent discussion of subjective probabilities, though I cannot say that my superficial understanding of QM gives me much confidence in any views I might hold about it.
The theory tells you the probability distribution of outcomes, which you’ll see if you repeat the experiment prepared the same way a bunch of times (frequentism!), and that’s all there is to it.
Well, the quantum probabilities are certainly frequentist. However, I don’t suppose strict Bayesians deny that there are probabilities with frequentist interpretation. I am also not sure about the label ensemble interpretation. It seems that its proponents somehow deny the validity of QM for small, non-ensemblish systems, which is a position I don’t subscribe to. After all, both collapse and many-world interpretations are no more Bayesian and no less frequentist than the ensemble one. The hidden parameters are deterministic, but have their own well known problems.
As for the frequentist-Bayes controversy, although I am probably more than you sympathetic to the Bayesian position, I have some sympathy for frequentism. I think both interpretation can coexist, with different sensible meanings of “probability”.
This relates to the discussion where you’ve apparently participated, and I am not sure whether I can say more. I am quite content with the prediction of the theory, and don’t trust much the feeling of need of further verbal explanation here. If I were pressed to say something, I would say that probably the present formalism of quantum theory isn’t particularly well suited for human intuition. After all, I believe we will get better formalism in future, whatever it means.
The feeling that the collapse is needed somehow to mediate the bomb’s interaction with the detector falls to the same category with the belief that light must propagate in some medium, or a feeling that there must be some absolute time. Such intuitions are sometimes correct, more often wrong.
Based on my experience, most of the ordinary physicists don’t think interpretations of QM are a big issue. It isn’t discussed too often, people are content to do the calculations most of the time. Of course, this may be different among the first-rank researchers.
Just to clarify: in that discussion, I claimed that the bomb tester thought-experiment doesn’t pose any principal difficulty for Copenhagen relative to the standard variations on the double-slit experiment, so that might seem to contradict what I write here. What I meant to say there is that the main feature of the bomb-tester, namely the interaction-free measurement, is also featured in a less salient way in these classic though-experiments, so that Copenhagen also makes sense for the bomb tester if you accept that it makes sense at all.
But if I may ask, how would you reply to the following statement? “Consider the case when we have a dud bomb, and a case when we have a working bomb that doesn’t explode. There is an observable difference between what the detector shows in these outcomes, so replacing the dud bomb with a working one changed the system in a measurable way. We call this change—whatever exactly it might be—collapse.”
Do you believe that this statement would be flawed, or that it is, after all, somehow compatible with the idea that “the collapse is only a mathematical tool”?
Comparing a system with a dud to a system with a working bomb is comparing two different systems, or the same system in two instances with different initial conditions, and thus doesn’t relate to the collapse. I suppose you rather had in mind a statement: “Consider two experiments with a working bomb, and in one the bomb explodes, while in the second it doesn’t. There is an observable difference...”
Well, it is undeniable that there is a difference. The two systems were the same in the beginning and are different in the end. There are three conventional explanations. 1) The systems were different all way long, but in the beginning the difference was invisible for us (hidden parameters). 2) The difference emerged from a non-deterministic process before or during the measurement (collapse). 3) There is no difference, but we see only a portion of reality after the measurement, and a different one in each of the cases (many worlds).
I suggest fourth point of view: Don’t ask in what state the system is, this is meaningless. Ask only what measurement outcomes are possible, given the outcomes we had from the already performed measurements. If you do that, there is no paradox to solve.
prase:
Actually, that’s the distinction I missed! The notion of “collapse” specifically refers to a non-deterministic process, not to a deterministic process that would at some point reveal the previously existing hidden variables.
That would basically be the “ensemble interpretation,” right? The theory tells you the probability distribution of outcomes, which you’ll see if you repeat the experiment prepared the same way a bunch of times (frequentism!), and that’s all there is to it. I do have a lot of sympathy for that view, as you might guess from the recent discussion of subjective probabilities, though I cannot say that my superficial understanding of QM gives me much confidence in any views I might hold about it.
Well, the quantum probabilities are certainly frequentist. However, I don’t suppose strict Bayesians deny that there are probabilities with frequentist interpretation. I am also not sure about the label ensemble interpretation. It seems that its proponents somehow deny the validity of QM for small, non-ensemblish systems, which is a position I don’t subscribe to. After all, both collapse and many-world interpretations are no more Bayesian and no less frequentist than the ensemble one. The hidden parameters are deterministic, but have their own well known problems.
As for the frequentist-Bayes controversy, although I am probably more than you sympathetic to the Bayesian position, I have some sympathy for frequentism. I think both interpretation can coexist, with different sensible meanings of “probability”.