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vzn
vzn
12:59 AM
@ThomasKlimpel thx for ref. by calling it a "diatribe" am not downplaying it, it looks like a fun read... the kind that few serious physicists would take very seriously... am a huge schroedinger fan, think hes a superhero. ok, it has no refs to "copenhagen" and no refs either, my main immediate question.
 
 
3 hours later…
More Anonymous
More Anonymous
3:55 AM
@vzn Most practioners of QFT know Copenhagen is problematic
13
A: What is the Copenhagen interpretation of quantum field theory?

Arnold NeumaierThe Born rule (and hence any discussion of collapse in the sense of the Copenhagen interpretation) is relevant only when an observer has made a distinction between a (tiny, observed) system and its (huge, observing) environment (= everything else, containing in particular the measurement equipmen...

 
 
6 hours later…
glS
glS
9:45 AM
look, I don't know your background, but that's just not what the paper is saying. I am used to say things in a way that gives the impression that I'm not as confident of what I'm saying than I actually am, as that's usually a good idea, but allow me to stop understating things for a moment here: there is not a chance in hell that they are claiming to be observing new physics in that paper. That's just not how the abstract would be written if that was the case.

Now, they might of course still be observing new physics without realising it (spoiler: they are not), but they certainly aren't sa…
I haven't had the chance to go through ACM's answer properly yet, as I think I'll also need to read a bit more into the paper for that. But it did lead me to read up again a little bit about "weak measurements", as that's something that never actually clicked for me.

Isn't a "weak measurement" just a projective measurement with a projector whose trace is larger than 1? In other words, something like having a four-level system and asking a question like "is the state in one of the first two levels?" (possibly generalising this idea to continuous variable systems). Or is it more complicated …
 
Mithrandir24601
Mithrandir24601
@glS I think you could formulate a weak measurement like that, although a more typical construction would be to weakly couple whatever you're measuring to some other system, then project the other system
but yeah, the important bit is that you're not fully collapsing (hence, not fully 'measuring') the system
 
 
7 hours later…
vzn
vzn
4:32 PM
@Mithrandir24601 ok can you clarify why this is "misleading terminology from weak measurements"? am not too familiar with weak measurements but now my main question is about |D> which is a "DARK" state. doesnt standard QM fundamentally not talk about "DARK" states because they are by definition unmeasureable? also am looking into/ thinking about the rabi driving after ACM mentioned it, and think part of his answer might be off on it.
@glS seems youre getting emotional about this. maybe you could define what you mean by "new physics." maybe there is some disconnect here. by some definitions, there has been no new physics in over a century. by other definitions, they happen daily. can you give any example of new physics less than 1decade old?
meanwhile, have been reading up on wikipedia entries myself and finding lots of related material, eg
Weak measurement
In quantum mechanics (and computation & information), weak measurements are a type of quantum measurement that results in an observer obtaining very little information about the system on average, but also disturbs the state very little. From Busch's theorem the system is necessarily disturbed by the measurement. In the literature weak measurements are also known as unsharp, fuzzy, dull, noisy, approximate, and gentle measurements. Additionally weak measurements are often confused with the distinct but related concept of the weak value. == History == Weak measurements were first thought about...
 
Mithrandir24601
Mithrandir24601
@vzn You can't say that something is or is not in any given state, unless you've just projected onto that state and are ignoring errors
(Or have projected onto some state, performed an operation which you know gives you a certain state, then ignored errors)
If you're inferring what a state is, you're not projecting onto it, you're saying that 'if we were somehow able to know what the state is without interacting with it in any way, this is what we'd measure the state to be, on average'
This isn't what the state actually is
Point being that if you say 'the state is ...' without some kind of projection involved somewhere, you've already made certain assumptions about how quantum physics works, so it's a totally false argument to use this to say '[this interpretation] is wrong', because that's an assumption of your statement, not a result
 
vzn
vzn
5:11 PM
@Mithrandir24601 as you highlighted, they are not talking "specifically" about interpretations at all in their writeup, its experimentally focused. its the popsci articles that extracted it immediately. but are you saying |D> is not technically a QM state, because there is no observable associated with it? are we in agreement on this?
 

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