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  1. A. Neumaier

    I How to derive Born's rule for arbitrary observables from Bohmian mechanics?

    I only claimed that it is a perceptible in the sense of the paper. The term is used only there, nowhere else.
  2. A. Neumaier

    A How do entanglement experiments benefit from QFT (over QM)?

    But before you had said, An ensemble of proton beams (prepared moving blops consisting of many protons) is not an ensemble of protons. Protons are never seen in the LHC experiments, prepared are the blops and measured are the traces of the collision products. In the spirit of the quote by...
  3. A. Neumaier

    A How do entanglement experiments benefit from QFT (over QM)?

    Nature ensures in perfect correlation experiments with entangled photon pairs (the ''certain experiments'') that whenever Alice measures $Ak$ to get ##a_k## then Bob measures $Bk$ and also gets ##a_k##, while for Bob it seems that his results are random. In spite of (and consistent with) the...
  4. A. Neumaier

    A How do entanglement experiments benefit from QFT (over QM)?

    Heisenberg didn't think of state reduction as being outside of quantum theory but (like most physicists since him) as being an aspect of it.
  5. A. Neumaier

    I How to derive Born's rule for arbitrary observables from Bohmian mechanics?

    But the argument (2) given there is for an idealized model case, where (in the interaction picture), the interaction has no off-diagonal terms in the selected basis. This seems appropriate only if the selected basis is invariant under the dynamics of the system alone (before the interaction...
  6. A. Neumaier

    I How to derive Born's rule for arbitrary observables from Bohmian mechanics?

    This is linearity, not unitarity. Unitarity seems to be lost in the assumption (3). Please justify this step from unitary dynamics.
  7. A. Neumaier

    I How to derive Born's rule for arbitrary observables from Bohmian mechanics?

    Are the three derivations mathematically equivalent? I looked at https://arxiv.org/pdf/1811.11643.pdf = since you are its author: This is not strictly on topic here but how do you reduce to position the color of an object (surely a perceptible) sitting at the macroscopic position x? It is...
  8. A. Neumaier

    I Bracket VS wavefunction notation in QM

    No. Many typical Dirac kets - such as ##|x\rangle## - are not vectors in a Hilbert space!
  9. A. Neumaier

    A How do entanglement experiments benefit from QFT (over QM)?

    Situations like these are precisely what induced Heisenberg 1927 to talk about state reduction (aka reduction of the state vector, aka collapse). That you don"t like the commonly used words for it doesn't mean that you don't make use of the same concept.
  10. A. Neumaier

    A How do entanglement experiments benefit from QFT (over QM)?

    I had done so in an earlier post to the same topic: It is a meaningful play with words. It means that something happens at a distance - namely that nature cooperates globally at long distance to ensure that the perfect nonclassical correlations predicted by quantum mechanics in certain...
  11. A. Neumaier

    B Continuity of photons

    What is strange?? What you wrote does not contradict what I wrote.
  12. A. Neumaier

    B Continuity of photons

    The detection failures are independent. But assuming 100%efficiency, two photons imply two detection events. This has nothing to do with correlations.
  13. A. Neumaier

    I Direct products of states

    In this case you need to rearrange the 4 entries of the matrix into a vector of length 4 in a way conforming to the content, usually rowwise or columnwise.
  14. A. Neumaier

    B Continuity of photons

    If only one photon is around at the time of measurement, there can be only one detection event. (But you seem to be discussing here the case of an entangled pair of photons, an idler photon and a signal photon. For this, there are two possible detection events.) No. One can detect a given...
  15. A. Neumaier

    I Direct products of states

    The simplest way to look at the tensor product of two Hilbert spaces of n-dimensional vectors representing two systems 1 and 2 is as a space of ##n\times n## matrices. n=2 for two spins. The general pure state is such a matrix ##\psi##, and the inner product is...
  16. A. Neumaier

    I How to derive Born's rule for arbitrary observables from Bohmian mechanics?

    Where can I find a reference to a derivation of Born's rule for arbitrary observables from Bohmian mechanics?
  17. A. Neumaier

    A How do entanglement experiments benefit from QFT (over QM)?

    BM has additional variables that makes the position basis preferred, and if one only looks at probabilities for position alone, these integrate to 1. In contrast to standard quantum mechanics, these are the only probabilities that matter in BM. Indeed, BM has no probabilities for spin or...
  18. A. Neumaier

    B Continuity of photons

    Nevertheless, the only correct B-level answer to the original question is no. The experimental evidence is overwhelming that a photon passing undetected a slit always results in zero or one screen point, never more. A zero count is due to detector inefficiencies. On the other hand, if the...
  19. A. Neumaier

    A How do entanglement experiments benefit from QFT (over QM)?

    Suppose a beam is split into a superposition of two beams. At positions where the two beams are very far apart, a beam dump collapse is obtained if one destroys one of the resulting beams (by position measurements there) and makes measurements on the other one. This is a bilocal activity created...
  20. A. Neumaier

    I Bracket VS wavefunction notation in QM

    Only in finite-dimensional Hilbert spaces. There kets may be viewed as column vectors (matrices with one column) = vectors of ##C^N##, bras as row vectors (matrices with one row) = covectors = linear forms, and the inner product is just the matrix product of these. But in order that the...
  21. A. Neumaier

    A How do entanglement experiments benefit from QFT (over QM)?

    Why does the beam dump define a subensemble with sz=+ℏ/2? Only because you collapse the superposition to something pure!
  22. A. Neumaier

    A How do entanglement experiments benefit from QFT (over QM)?

    The preparation of many independent systems may define an ensemble in the quantum case, but then it is not consistent with what you describe here: But a Stern-Gerlach experiment does not constitute a measurement: it is a unitary operation. Thus in such an experiment you are not sorting...
  23. A. Neumaier

    B Continuity of photons

    No. There is always some loss due to detector inefficiency. The 1-1 correspondence is just a convenient simplification.
  24. A. Neumaier

    A Bosonic Field operator in this exponential

    Taking the exponential of a distribution is ill-defined and needs a regularization to give it a meaning. The result is a state not described by the original Fock basis.
  25. A. Neumaier

    B Authorities in science

    That was indeed the context in which ftr posted his original query (if you follow the links in post #1 a few steps backward). But I don't really have a concern, I can live easily with the way science is done in our culture.
  26. A. Neumaier

    A How do entanglement experiments benefit from QFT (over QM)?

    The same. But your definition conflicts with your earlier usage of the word subensemble, which makes no sense with this meaning. Hence I wondered what you mean. Or does your notion of ensemble have some sort of temporal permanence so that it remains the same when you change its momentum through...
  27. A. Neumaier

    B How to teach beginners in quantum theory the POVM concept

    Nothing is wrong per se. But there is the blemish that you create your example in a way that presupposes Born's rule. The Gaussian used in the introductory lab to analyze a sample of measurement results has little to do with the Gaussian used to model a POVM. For in the POVM, all positions...
  28. A. Neumaier

    B Authorities in science

    What about the incidents recently discussed in Peter Woit's blog?
  29. A. Neumaier

    B Authorities in science

    Yes. tradition in the form of Lehrmeinung has a lot of authority. In the case of Copenhagen even though there always have been prominent opposing authorities, such as Einstein and Schrödinger.
  30. A. Neumaier

    A How do entanglement experiments benefit from QFT (over QM)?

    I know that you call it that. But I still do not know what properties of a physical setup makes it qualify as an ensemble in your sense. You are using the term without explaining what it should mean. I provided a detailed example for momentum measurement in the POVM thread.
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