Too bad, the paper has been withdrawn due to a mistake :-/
...(continued)Maybe. But if your solution was not only self-consistent but also "single-world" then it would certainly contradict our theorem.
@Jonathan: I am unsure whether the concern you had is related to ($\star$), too, but I would anyway be interested to know whether it is this type of statements that you
If I had a self-consistent answer to that I'd be able to solve the measurement problem, no?
...(continued)OK, then we have identified the point where we disagree. Our assumption (QT) indeed corresponds to ($\star$), together with the understanding that the state is physically relevant.
Having said this, I am still curious to know how, in your opinion, experimenter F1 should derive her prediction ab
Yes, I would say so.
Could one then summarise your viewpoint as follows: Statement ($\star$) by itself is correct, but the state $\psi$ of the system is not the one that is physically relevant (i.e., we should not use it to deduce claims about the outcomes of future measurement on the system, for instance)?
...(continued)I think our point of disagreement is not $(\star)$ in itself, but rather the relevance of $\psi$ that enters this statement. I would also make the second bullet point stronger.
- When discussing erasure and subsequent measurements, one needs to keep track of both $E$ and $S$, even if they are no
...(continued)Yes, it may be easier to chat about this in person. But since I know a few who are following this discussion, let me at least summarise the points where I agree with you:
- In a scenario where experimenters are themselves subject to quantum measurements, it is not allowed to describe them using c
...(continued)The point I was originally trying to make was that the experimenter must be treated within the same framework as the system. The argument I was trying to make was that it is not always justified to treat the experimenter as classical (what I said above regarding the environment can be rephrased to t
...(continued)The example itself makes sense to me. However, I am unsure how it connects to the questions we were discussing.
Certainly, it illustrates that the statement ($\star$) mentioned earlier would be wrong if there was a non-trivial exchange Hamiltonian governing the interaction between experimenter a
...(continued)In a sense, yes, that's what I'm saying.
Let me take a situation that is very familiar to me: Cavity QED. We model a single-mode field inside a cavity with leaky mirrors by means of an interaction Hamiltonian like $\hat{H}_\text{int}=\mathrm{i}\hbar\int\mathrm{d}\omega\ \kappa(\omega)\bigl[\hat{b}(
...(continued)Just to make sure I got this correctly, are you saying that (at least in certain situations) the predictions we obtain when we use quantum theory depend on where we make the split between quantum system and measurement device? (This would raise the question whether there is a rule that tells us wher
...(continued)I won't attempt to solve the general problem. At least not without some beers.
My point was directed at the particular argument at hand.
- I have a laboratory $L$ inside which is a quantum system $S$ and an experimenter $E$
- $E$ performs some measurements on $S$, but $E$ is not treated as part
...(continued)I agree with what you wrote in the last paragraph — you may even regard this as an implication of our Theorem 1 (at least provided that you take SW for granted).
I nevertheless have difficulties making full sense of the position you take. If I understand it rightly, the ultimate conclusion would
...(continued)The ability to impose a "cut" and isolate a system (e.g., a single H atom) from its surroundings and treating that system as a quantum object disconnected from its surroundings, or connected to them solely by means of classical channels, is an extremely convenient fiction. But it is, at the end of t
...(continued)My previous statement must have been ambiguous. But when I wrote that an experimenter applies quantum theory to a system, I did not mean to imply that she applies classical theory to its surroundings. Rather, the idea was that she can use QT to study any arbitrary subsystem of the universe, provided
...(continued)My understanding of quantum theory is precisely that: It must be applied to the experimenter themselves as well as the apparatus. I come from the school of thought that believes that everything is quantum.
As per my previous comment, within this framework it may be possible that your paper could
Indeed, our argument is based on the idea that any experimenter is free to use quantum theory to describe the world *around* her (but not including herself). If I now understand correctly, you are saying that this is not in general a correct use of quantum theory. Did I get this correctly?
I don't think that QIC is to blame here. ECCC is also not indexed by google scholar for some strange reason. Try this paper http://eccc.hpi-web.de/report/2016/073/ for instance.
...(continued)You are perfectly right; that is exactly what confused me.
Personally, then, I feel slightly uneasy with saying that your property QT captures quantum mechanics, since I believe strongly that quantum mechanics must describe the state of the experimenter themselves. This is especially pertinent in
...(continued)I agree with what you are writing about $\psi_L$. While the state of the prepared system $S$ does not depend on whether $E$ remembers it, the state $\psi_L$ (which includes $E$) does.
I am not sure though what you meant when you wrote that $\psi_L$ is the "relevant object". Note that property QT
...(continued)Actually, the Bayesian perspective did not enter my mind.
I *almost* agree with the reformulation you give in your second paragraph. I say "almost" because of one detail that I feel is important in the context of your paper, and which for me is the key issue at stake here.
Suppose I have a lab
...(continued)I am not sure why you think that the state $\psi$ must change. But one guess I have (please correct me if I am wrong) is that you take a Bayesian perspective, in which case there may be an ambiguity in the interpretation of time t. So, maybe, you interpreted t as the time when the prediction was mad
...(continued)This paper somehow got published in QIC. Not that I would encourage anyone to read it, but let's say you wanted to...
Well, you would probably just [look up][4] the published version on Google Scholar.
What a bummer(!), it's not there... Maybe that's just because the paper's name has changed?
...(continued)Dear Renato, may I also join the chorus and thank you for being so accessible and willing to discuss your results publicly. I've been following this thread since its inception but have so far resisted contributing.
Please correct me if I am wrong, but does not a full description of $\psi$ require
...(continued)looks like a nice paper. People have looked at how to do wavelets with quantum circuits and i don't see any of these papers referenced, i.e.
http://arxiv.org/abs/quant-ph/9702028
http://arxiv.org/abs/quant-ph/0001077
http://arxiv.org/abs/quant-ph/9909014
so how different are the quantum circuits
...(continued)Practicalities are indeed irrelevant here, so we can certainly focus on the last question you pose. But let me first restate more precisely what we use in our argument. In the special case of a system with trivial Hamiltonian between time t=0 and t=1, the relevant statement reads as follows: “If an
...(continued)I have a question, relates to:
However, since the non-gravitational physics has been accurately explained by the principles of quantum mechanics, it seems necessary that General Relativity is merged with quantum mechanics.
but the quantum principles at first emerged from boundary conditions in th
...(continued)Well, one answer to that question is that a memory recording (or recording of a preparation) is so redundantly encoded in the environment, that it is practically impossible to undo it. Of course, one could theoretically undo it, by performing the operation on all the copies of the information, which
Note that A and W carry out their measurements at the end of the experiment (i.e., there is no further measurement). The resulting entanglement is hence irrelevant.
...(continued)Interesting question. But doesn't “recording a value” mean that we prepare a system (the “memory system”) in a certain state and then assume that it will stay in that state? So, unless we make a distinction between “memory systems” and “normal quantum systems”, the potential problem you are mentioni
...(continued)Thanks. So, taking the example of a quantum contextuality proof where I undo one of the measurements, is it fair to say that the distinction you are making with your experiment, is that the thing which is undone is a preparation and not a measurement? Is it not just as problematic to ascribe values
...(continued)Thank you for clearing that up. But wouldn't the entanglement with A and W creates an external record of the states of F1 and F2' labs and bring me back to the same problem? That is, starting from $ |T\rangle |\downarrow \rangle |\text{ok} \rangle_{AW} $, to infer $ |T\rangle |\rightarrow \rangle |\
...(continued)Note that states of the form $|\downarrow\rangle_{F2}$ are meant to be states of the entire lab of experimenter F2. (I am sorry if this was unclear.) Hence, in the particular case you mention, the electron is automatically included in the description because it is within F2's lab. But you are of cou
...(continued)Hi. I'm also worried about erasing a measurement record but in the inferential step (26)=>(35).
The gist of the argument seems to lie entirely in these two terms of the Hardy state (ignoring the normalization): $$ |T\rangle |\uparrow \rangle + |T\rangle |\downarrow \rangle = |T\rangle |\rightarrow
...(continued)The crucial fact to notice is that the derivation of Eq. 25 relies entirely on standard quantum mechanics (applied from the viewpoint of F1): If a system is prepared in a state $\psi$ and subsequently evolves according to a unitary $U$ then its state will be $U \psi$ (and a measurement will give an
...(continued)Yes, exactly -- thanks for the prompt response. Lluis Masanes observed further that by invoking special relativity, one can have different observers who would make different statements about actual measurement records that would be consistent in their reference frame, but if they tried to get togeth
...(continued)at first I tried to satisfy the chiral symmetry, in that place, I thought that the chiral symmetry breaking is due to vacuum classical polarization, and this problem is solved by dual behavior of fields, some of these notes are in the first paper http://iiste.org/Journals/index.php/APTA/article/view
...(continued)Regarding your question about the measurement records: You are right that the values r, z, x, and w are not at the same time available. But r and z, for instance, can be accessed simultaneously (at time n:20), which justifies the statements involving only these two (e.g., our Eq. 26). The same holds
...(continued)Hi Renato, yours and Daneila's paper has generated a lot of discussion, and today, Will Matthews presented it to our group at UCL. A question: in deriving the contradiction are you not ascribing results to measurements which are later undone/erased? So at the end of the experiment, there is no measu
...(continued)Hi Marco,
Thank you very much for taking the time to reply to my message! I really appreciate it! I think I fully understand what you mean until now. We should state the notion of cone and the relation between our results and the notion of cone. We will try to give an objective and precise expres
Great figures! Looking forward to reading this one.
...(continued)at first I tried to remove x1=x2 from the propagation
https://www.docdroid.net/TYzB01L/the-time-stop-in-the-quantum-fields-fluctuation.pdf.html
the propagation modification is legal according to remove x1=x2
to satisfy the symmetries I related that modification to dual fields behavior, as I think
...(continued)Hi Bang-Hai,
thank you for your message, and my apologies: I have intermittent internet connection and a decently long reply of mine got lost because of that :-( Unfortunately I do not have the time to rewrite it in full.
What I meant is that people have known for quite some time about the du
...(continued)Hi Marco,
Right! Thank you for your mathematical explanations and clarifications, I really appreciate it! Could we add your pointing to our new version?
Frankly, we try to clarify more notions and results and connections among them, physically, not mathematically (It is also the reason that we ha
...(continued)I am not sure where this goes (I have only skimmed through the first part of the paper), but what the author seems to find unexpected is the notion of cone dual to a cone, and the fact that the cone of positive operators is self-dual, while entanglement witnesses are dual to separable operators, etc
Some of the figures in your bound entanglement paper look spookily like some of our graphs! Thanks for highlighting these connections Māris, I appreciate it.
...(continued)You introduce some very interesting concepts in this paper! I just wanted to point out some connections that might be interesting to explore.
**Hamiltonian complexity**
The density matrix in your eq. (2) looks exactly like 2-local Hamiltonian that encodes classical computation in its ground state
...(continued)Granted that it would yield a different story if A were to perform the interference experiment instead, but it's certainly a story quantum mechanics allows us to tell---and that story depends on $z$ being indefinite in value. And one could also tell a combined story, in which A randomly chooses whet
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