 |
|
|
|
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Am 18.09.2011 18:27, schrieb Darren New:
> On 9/18/2011 1:02, Patrick Elliott wrote:
>> The *real* trick is the fact that you can create conditions
>> where you "know" what the outcome will be, instead of just looking
>> into the
>> box to find out.
>
> That's exactly what the quantum eraser does, and if you don't look at
> the result, you don't get interference. That's precisely the point I'm
> making. You get interference at time T by taking a measurement at time
> T+D, where D is a timelike separation from T.
Something's wrong there, because it would allow me to define a protocol
to transfer information back in time:
- At time T+D, I decide wheter I take a measurement or not depending on
some information.
- At time T, I check whether I get interference or not, which tells me
whether I'll be measuring at T+D, which in turn gives me the desired
information.
Last not least, I could even base my decision whether to take a
measurement or not on whether I get interference or not - which would
obviously cause a problem with causality.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On 9/18/2011 9:27 AM, Darren New wrote:
> On 9/18/2011 1:02, Patrick Elliott wrote:
>> The *real* trick is the fact that you can create conditions
>> where you "know" what the outcome will be, instead of just looking
>> into the
>> box to find out.
>
> That's exactly what the quantum eraser does, and if you don't look at
> the result, you don't get interference. That's precisely the point I'm
> making. You get interference at time T by taking a measurement at time
> T+D, where D is a timelike separation from T.
>
Well.. Yes and no. The quantum eraser "changes the conditions" withing
that D time frame, such that the transition to a state is interrupted,
by inserting a new set of conditions that allow for the prior quantum
state. Since the transition never took place, no state change happened.
Basically, it is the equivalent of deciding, at the last possible
instant, to not open the hypothetical box, to look inside. That you
rigged the box lid, before hand, such that the result "must" be what you
wanted, doesn't change the fact that you never really opened it, so your
"rigged" conditions never came into play (or, rather, in this case, you
jiggled the poison container, but didn't break it).
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On 9/18/2011 9:25 AM, Darren New wrote:
> Again, this is contradicted by experimental evidence.
>
> Unless you have something else to point to, that shows where an
> experiment where the scientists took a measurement but then didn't look
> at it still caused the collapse?
>
:head desk: ?? This is nonsense. You can't take a measurement without
causing a collapse *period*. Try talking to an actually physicist about
that, and not Depok Chopra. Measurement, by definition, means that your
test particle had to have an effect on another particle. It is not
possible to do that, without both particles affecting *each other*, thus
triggering the collapse. The measurement *is* the observation, and the
test equipment *is* the observer. That some other later on read a
computer screen, and went, "Yup, the particle hit the detector.", is
irrelevant to the result. It was already "observed" by the measuring device.
Or, do you have some magical way to "measure" this stuff, which somehow
doesn't involve particle collisions?
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On 9/18/2011 15:31, Patrick Elliott wrote:
> Well.. Yes and no. The quantum eraser "changes the conditions" withing that
> D time frame, such that the transition to a state is interrupted, by
> inserting a new set of conditions that allow for the prior quantum state.
Right.
> Since the transition never took place, no state change happened.
Right. Indeed, that's the point of the experiment. That it is *not* the
case that the particle went through one slit or the other or both.
You said
> A real cat would already invalidate the experiment, as would anything
else you might use, like a sheet of radiation sensitive material
But that's clearly not the case, if what you're measuring is whether the
particle went through one slit or the other or both or neither.
Other than that, you're pushing the analogy too far for me to track what
you're talking about.
--
Darren New, San Diego CA, USA (PST)
How come I never get only one kudo?
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On 9/18/2011 15:38, Patrick Elliott wrote:
> Measurement, by definition, means that your test
> particle had to have an effect on another particle.
No. That's the entire point of using an entangled particle. The particle
you're checking for interference is never touched by the rest of the experiment.
> It is not possible to do
> that, without both particles affecting *each other*, thus triggering the
> collapse.
Yes. And that's the funky part, now isn't it? I'm not sure why you first
bang your head on the desk, then agree with me.
> The measurement *is* the observation, and the test equipment *is*
> the observer. That some other later on read a computer screen, and went,
> "Yup, the particle hit the detector.", is irrelevant to the result. It was
> already "observed" by the measuring device.
Yes, in this case. Again, I'm not sure why you seem to be disagreeing with me.
> Or, do you have some magical way to "measure" this stuff, which somehow
> doesn't involve particle collisions?
Yes. You split the particle into an entangled pair via spontaneous
down-conversion, then you interact with only one of the pair. Indeed, that's
the whole point of the experiment: you're *not* interacting with the
particle whose behavior changes based on whether you interact with the other
particle. Hence, it is nonsensical to say "the particle knows what slit it
went through" or something like that.
--
Darren New, San Diego CA, USA (PST)
How come I never get only one kudo?
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On 9/18/2011 4:32 PM, Darren New wrote:
> On 9/18/2011 15:31, Patrick Elliott wrote:
>> Well.. Yes and no. The quantum eraser "changes the conditions" withing
>> that
>> D time frame, such that the transition to a state is interrupted, by
>> inserting a new set of conditions that allow for the prior quantum state.
>
> Right.
>
>> Since the transition never took place, no state change happened.
>
> Right. Indeed, that's the point of the experiment. That it is *not* the
> case that the particle went through one slit or the other or both.
>
> You said
> > A real cat would already invalidate the experiment, as would anything
> else you might use, like a sheet of radiation sensitive material
>
> But that's clearly not the case, if what you're measuring is whether the
> particle went through one slit or the other or both or neither.
>
> Other than that, you're pushing the analogy too far for me to track what
> you're talking about.
>
What I am saying is that, in the case of the quantum eraser, you are
rigging things so that the event doesn't happen, or a different one
does. I think the confusion here is where the "observation" takes place,
and where the measurement does. In this case you have sort of decoupled
them. You are creating an "observer", which is affected by the particle,
and in turn begins collapsing its state, then you introduce a new
"observer", which either erases the result, or changes it to something
else, then you "measure" what happened as a result. The term "observer"
becomes more ambiguous in this case. A proper term would have been
"interactor", i.e., the thing that alters the state. The confusion
arises in that a) that isn't really a word, and b) they opted for the
misleading term "observer", when talking about how the state collapses.
In reality, the measurement doesn't have to happen when the first
observation takes place. It may not even be possible to measure that
interaction at all, save as a consequence of it having happened. Q.E.D.
Whether you measure the system or not, doesn't effect if something
happened, since measurement and interaction/observation are rarely
simultaneous, in *any* experiment, nor is the act of measuring critical
to the result.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On 9/18/2011 4:36 PM, Darren New wrote:
>> It is not possible to do
>> that, without both particles affecting *each other*, thus triggering the
>> collapse.
>
> Yes. And that's the funky part, now isn't it? I'm not sure why you first
> bang your head on the desk, then agree with me.
Not the entangled particles, I mean what ever "particle" in the device
you are using the trigger the effect desired, and which ever one of the
the entangled pair you are playing with, to produce that result. You
don't get an effect in a vacuum (well, you do, but the odds of a
collisions are a lot damn less likely lol), you have to have the
particle pair you are testing with "interact" with something. That
interaction, as I said in the other post, is almost never, if ever, the
measuring device. So, measurement is irrelevant to the problem.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On 9/19/2011 17:02, Patrick Elliott wrote:
> What I am saying is that, in the case of the quantum eraser, you are rigging
> things so that the event doesn't happen, or a different one does.
Right. Indeed, that's the point.
> the confusion here is where the "observation" takes place, and where the
> measurement does.
In a system where the measurement device isn't performed by a living
organism (i.e., most anything except the cat thought experiment) I don't
think it's useful to decouple those terms.
> the thing that alters the state.
And in the case of the quantum delayed choice eraser, what is "the thing"
that alters "the state"?
> b) they opted for the misleading term "observer", when
> talking about how the state collapses.
That's the problem. Nobody could come up with a reason that the state would
collapse at all. I'm not sure even now it's a solved problem.
--
Darren New, San Diego CA, USA (PST)
How come I never get only one kudo?
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On 9/19/2011 17:06, Patrick Elliott wrote:
> you have to have the particle pair you are testing
> with "interact" with something. That interaction, as I said in the other
> post, is almost never, if ever, the measuring device.
I don't understand how you decouple the two. You shoot a photon at a
photomultiplier. The photomultiplier emits a click. The interaction causes
the measurement. I don't know how you take a measurement without an
interaction of *some* sort, and I don't know how you interact with something
without taking a measurement unless you entangle your state with the device
with which you're interacting.
--
Darren New, San Diego CA, USA (PST)
How come I never get only one kudo?
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On 9/19/2011 6:11 PM, Darren New wrote:
>> the thing that alters the state.
>
> And in the case of the quantum delayed choice eraser, what is "the
> thing" that alters "the state"?
>
If what you are doing is "undoing" the stat change, then its still the
same thing as would have changed the state, uh.. sort of.. Yeah,
confusing, but its not quite so big of a problem as it first appears.
Something is still "effecting" the state, even if the "effect" is to
prevent a transition into one that is collapsed.
>> b) they opted for the misleading term "observer", when
>> talking about how the state collapses.
>
> That's the problem. Nobody could come up with a reason that the state
> would collapse at all. I'm not sure even now it's a solved problem.
>
I tend to think that they are either confusing themselves. There is no
reason it wouldn't. But, we think about things with language. So, if you
are using the wrong bloody language, it creates all sorts of errors in
thinking.
In principle, as long as a particle is isolated from influences that
"can" collapse the state, it won't. But, its an unstable arrangement,
and you can't even be certain to maintain it in a vacuum, given some
small odds that a virtual particle will happen to pop in and mess with
things. In a practical sense, it simply means that, if you don't alter
its unstable state, then it will change state when it hits something
else, just not what ever it was you where intended to "measure" it with.
After all, in this case, you are dealing with a photon, and your
"detector" is only in one very small area. If the thing hits something
where you can't see it, it still hits something, eventually, and..
without state collapses, the world would be awfully full of random
photons, which happened, by chance, to split, forming entangled pairs,
and yet where never "observed" in the sense described.
Personally, I consider the confusion over what happens if you don't
"see" it happen to be complete nonsense, like arguing that noise doesn't
happen if a tree falls without a observer, yet discounting that the
impact, and subsequent vibrations, still do. The distinction is absurd,
even if technically correct.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
|
|
