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entropy1
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In MWI, would you say that a measurement puts the observer in superposition of being in the various worldlines?
If I said "yes" to that, would I be correct?
If I said "yes" to that, would I be correct?
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entropy1 said:In MWI, would you say that a measurement puts the observer in superposition of being in the various worldlines?
The different worlds containing the different outcomes after Unitary evolution of the wave function?PeterDonis said:What worldlines are you talking about?
entropy1 said:The different worlds containing the different outcomes after Unitary evolution of the wave function?
I see this as a straight forward question.
entropy1 said:I would still like an anwer on the question in my OP.
Oh I see haha. Sorry.PeterDonis said:The term "worldlines" is normally used in relativity to mean something very different. That's why I was confused.
Ok thanks. That makes the thing less clear to me but that doesn't have to be a bad thing, to the contrary.PeterDonis said:With the clarification above, the answer to your OP question is that it is based on a false premise. The different outcomes are not in different "worlds" in the MWI. (Yes, that means the MWI is misnamed.) There is just one "world", in which the observer is entangled with the observed system. As is true of any entangled state, neither the observer nor the observed system has a well-defined state by itself. Only the full combined entangled state of observer + observed system is well-defined.
entropy1 said:is there in MWI no collapse?
So that leaves me wondering: do we get an entanglement between a single measurement device and the single thing it measured, or do we have to speak of more than one measurement device, since we get all possible pointer outcomes.PeterDonis said:With the clarification above, the answer to your OP question is that it is based on a false premise. The different outcomes are not in different "worlds" in the MWI. (Yes, that means the MWI is misnamed.) There is just one "world", in which the observer is entangled with the observed system. As is true of any entangled state, neither the observer nor the observed system has a well-defined state by itself. Only the full combined entangled state of observer + observed system is well-defined.
entropy1 said:do we get an entanglement between a single measurement device and the single thing it measured, or do we have to speak of more than one measurement device, since we get all possible pointer outcomes.
entropy1 said:Does the entanglement force us to experience a single outcome that depends on how we got entangled, for instance: if we get outcome A on the measurement, does that mean we got entangled with the particle being in state A? And likewise for the other possible measurement outcomes?
entropy1 said:the particles that make up the measurement setup are the particles that will get entangled with the observed particle, we speak of one machine, and thus of that one machine getting in superposition of outcomes, right?
entropy1 said:Could one also say that the particle got entangled with the observer? (I think not)
Thanks. Your answer is appreciated. With "one machine" I mean that there is no magical multiplication of the number of particles that makes up the measurement machine.PeterDonis said:What do you mean by "one machine" here?
entropy1 said:With "one machine" I mean that there is no magical multiplication of the number of particles that makes up the measurement machine.
So I think one could assert that the spawning of a copy of the universe is no multiplication of particles since the "new" universe is effectively isolated from its original. Or perhaps one could not speak of particles as ontological entities. I don't know what you mean actually by that question.PeterDonis said:What does "magical manipulation" mean?
entropy1 said:the spawning of a copy of the universe
entropy1 said:I don't know what you mean actually by that question.
I agree and that is my point in this case.PeterDonis said:Does not happen. We've already been over this. There is only one "universe"--one quantum system with one wave function that undergoes unitary evolution. Unitary evolution can't "copy" anything.
I looked it up: I ment (and wrote): "magical multiplication" (of which I think is implausible ). Perhaps there is a miscommunication.PeterDonis said:I thought it was obvious: I don't know what you mean by "magical manipulation", so I was asking you to clarify. Surely you realize that "magical manipulation" is not a standard physics term.
entropy1 said:I ment (and wrote): "magical multiplication"
entropy1 said:I agree
entropy1 said:think one could assert that the spawning of a copy of the universe is no multiplication of particles
Still a misunderstanding. You asked:PeterDonis said:You can't assert that "the spawning of a copy of the universe is no multiplication of particles" unless you believe that there is a "spawning of a copy of the universe". But there isn't.
Or, to put it another way, you were basically saying: "the universe gets copied, but particles don't get multiplied". But that doesn't make sense. If the universe does get copied, everything in it has to get copied too. So it has to be both, or neither. In fact it is neither.
So I anwered:PeterDonis said:What does "magicalmanipulationmultiplication" mean?
by means of response to that, meaning: if you (PD) mean to say that spawning a universe (if we would assert that, which we do not) is no "magical multiplication", then I quess... etc. In fact we are agreeing that there is no magical multiplication.entropy1 said:So I think one could assert that the spawning of a copy of the universe is no multiplication of particles since the "new" universe is effectively isolated from its original.
entropy1 said:by means of response to that, meaning: if you (PD) mean to say that spawning a universe
entropy1 said:In fact, my point is that the measurement machine does not magically multiply itself (into different branches).
PeterDonis said:There is just one "world"
entropy1 said:The particles that make up the machine represent all possible measurement outcomes according to MWI.
It is a miscommunication. You should read my response as: "Well, if you say that, why not say this and this?", not as my personal opinion, which we tripped over because I started the sentence with "So I think...(that if you say that...)". Perhaps it should have read: "So, I then think..." Besides that English is not my natural language. This hypothetical formulating can be confusing.PeterDonis said:Which makes no sense since I had already said in this thread that there is no such "spawning". Why would you answer a straightforward question by assuming a hypothetical you already know to be false?
Ah, that makes it even more clear (and you already said it, yes). The rest we agree about.PeterDonis said:Wrong. A correct statement would be: "the particles that make up the measurement device (I prefer that term to "machine" since the latter does not make clear what you are talking about) are entangled with the particles that make up the measured system". Neither the measurement device particles nor the measured system particles on their own "represent" anything since they are entangled. Only the full entangled system of measurement device plus measured system does.
So I'm wondering: (If you say that,) is the "whole system" then representing/consisting of all the possible (applicable) measurement outcomes? (Just to be clear on this)PeterDonis said:Wrong. A correct statement would be: "the particles that make up the measurement device (I prefer that term to "machine" since the latter does not make clear what you are talking about) are entangled with the particles that make up the measured system". Neither the measurement device particles nor the measured system particles on their own "represent" anything since they are entangled. Only the full entangled system of measurement device plus measured system does.
entropy1 said:You should read my response as: "Well, if you say that, why not say this and this?"
entropy1 said:I see now that you said that, but I did not read it today, I just proceeded in this thread today because I didn't want to start a new one.
entropy1 said:is the "whole system" then representing/consisting of all the possible (applicable) measurement outcomes?
As I said, it is a miscommunication, or maybe a little stack of miscommunications.PeterDonis said:And you should not even be asking "if you say that" if I have already said "not that". You can't expect me to read you as asking something I have already contradicted in an earlier post.
You responded:entropy1 said:If the particles that make up the measurement setup are the particles that will get entangled with the observed particle, we speak of one machine, and thus of that one machine getting in superposition of outcomes, right?
I responded:PeterDonis said:What do you mean by "one machine" here?
Your question:entropy1 said:Thanks. Your answer is appreciated. With "one machine" I mean that there is no magical multiplication of the number of particles that makes up the measurement machine.
If there is one machine, then I mean by that there is no magical multiplication.PeterDonis said:What does "magicalmanipulationmultiplication" mean?"
meaning: "Well, if you put in question that there is no magical multiplication, one could well say that..."entropy1 said:So I think one could assert that the spawning of a copy of the universe is no multiplication of particles since the "new" universe is effectively isolated from its original. Or perhaps one could not speak of particles as ontological entities. I don't know what you mean actually by that question.
Ok.PeterDonis said:And, as you should now realize, that is a bad idea. We have discussions in threads for a reason. You should not just ignore the information in previous posts before making new posts.
entropy1 said:As I said, it is a miscommunication, or maybe a little stack of miscommunications.
entropy1 said:I started
I think I actually did read back the thread. I think I was eager and focused formulating the new question. It probably would have been better if I'd started a new thread.PeterDonis said:You just need to read previous posts before making new ones.
entropy1 said:It probably would have been better if I started a new thread.
entropy1 said:I think one could assert that the spawning of a copy of the universe is no multiplication of particles
So you're saying it is a question of bad use of the English language? I have said what I meant by that sentence.PeterDonis said:Even then my response to your question would have been the same, basically: "there is no spawning of universes, so your statement doesn't make sense".
You say you meant your statement as a hypothetical--"what if this were the case"--but your statement was this:
That is not a hypothetical; it's just a flat statement. A hypothetical would be something like this:
"What if multiple copies of the universe were spawned when a measurement was made? Could we still say there was no multiplication of particles?"
entropy1 said:So you're saying it is a question of bad use of the English language?
I could agree with that.PeterDonis said:Given your description of what you actually intended to say, yes.
Meaning that there is one machine and one universe that don't get multiplicated (magically).entropy1 said:Thanks. Your answer is appreciated. With "one machine" I mean that there is no magical multiplication of the number of particles that makes up the measurement machine.
PeterDonis said:Does not happen. We've already been over this. There is only one "universe"--one quantum system with one wave function that undergoes unitary evolution. Unitary evolution can't "copy" anything.
So, my question do the particles of the measurement device represent the outcome, and in fact all possible outcomes simultaneously?PeterDonis said:Of course, since the wave function contains all possible measurement outcomes.
entropy1 said:do the particles of the measurement device represent the outcome, and in fact all possible outcomes simultaneously?
entropy1 said:thanks for taking the effort to educate me.
The Many-Worlds Interpretation is a theory in quantum mechanics that suggests that every possible outcome of a measurement or observation exists in a separate parallel universe. This means that instead of a single universe, there are multiple universes branching out with every possible outcome.
Observer superposition in MWI is the idea that the observer, or the person making a measurement or observation, also exists in multiple parallel universes. This means that the observer's consciousness is split into different versions, each experiencing a different outcome of the measurement.
Unlike other interpretations of quantum mechanics, such as the Copenhagen interpretation, MWI does not require the collapse of the wave function upon observation. Instead, it suggests that all possible outcomes of a measurement exist simultaneously in different universes, including the observer's experience of the measurement.
Currently, there is no direct evidence to support the MWI theory. However, some scientists argue that the theory is consistent with the laws of quantum mechanics and can explain certain phenomena, such as the double-slit experiment, which other interpretations struggle to explain.
If MWI is true, it would mean that there are an infinite number of parallel universes, each with slightly different versions of ourselves and our reality. This could have significant implications for our understanding of the universe and our place in it, as well as potential applications in fields such as quantum computing and time travel.