If by this you mean that currently QM does not imply/indicate/suggest that something is real, then I understand. I was going beyond QM saying something must exist, but that is not a supportable viewpoint in this QM forum (as should be). Saying it does not exist is likewise not supportable.
I don't think I am confused. I think people are being loose and fast with their definitions.
For example, you stated
Which implies there is something that is being interacted with as it is measured.
I fully understand that IN QM the real things are the observations, and that, currently, QM...
We can create a QM system with a defined state out of real objects, but, once we do that, those objects no longer exist? I can understand that QM is saying nothing about the nature of the system beyond what will happen when it is measured/*/, but how can that be interpreted as not existing?
It seems, since we can describe and produce systems in which we can mathematically represent the state of a system before and after observation/interaction/measurement, that therefore something exists in a real sense just before the measurement/*/. That seems obvious (to ignorant me). Is QM...
What you said: If the Schrodinger equation for the system says they are in superposition while entangled with the environment, then they are (obviously).
I'm just saying that achieving that superposition in the lab would be "difficult", an unscientific subjective judgement. Are you saying...
I thought that decoherence indicated that one has pretty much pinned down the relationship between a thingy and its entangled environment. It appears like a classical state, but there is no such thing as a classical state (if you are accepting no-collapse decoherence). At the scope of a card...
This paper has some biological examples
Experimental motivation and empirical consistency
in minimal no-collapse quantum mechanics
Maximilian Schlosshauer
http://arxiv.org/abs/quant-ph/0506199v3
I just want to state my view to see if it is in line with what the experts think. (not a pet theory, just my understanding)
Roughly, Things can have superpositions of states at scales where they are not interacting a lot with other things. A particle can have a superposition of states until it...
Note that when you say 4lb = 4lb, you are saying the number of pounds are equal. You have assigned units, which makes it "more understandable" in a way. When you say 2 = 2 with no units its difficult to say what a standalone 2, with no units, represents other than the value or state 2. So how...
He explains it in this lecture. Maybe it will help.
http://vega.org.uk/video/programme/46
You might watch http://vega.org.uk/video/programme/45 first (or not)
It isn't so much that "one can know" which slit, but that the particle going through a slit becomes different than a particle through the other slit, so they are no longer coherent. The loss of coherence means no interference pattern. When you learn the math you will see easily that if the...
All you can really say is that when you measure a particle it will show one of the expected values with probablities as predicted. No one know why. It is the basis of QM. You can go on to call it collapse, world splitting, or whatever, but that becomes religion.
Personally I like the...
Are you asking for experimental verification of Bell Inequality Violation? There are many writeups available through Google.
http://en.wikipedia.org/wiki/Bell_test_experiments (up to 18Km)
If that isn't what you are asking, please try again.
That is not exactly correct. Rather, one can say that in a simplistic entangled two particle system in which each particle will be measured, measuring 1 particle will give you information about what the other particle will give when measured. The measurements will always correlate. Measuring...
If you want to cheat (jump ahead) try this lecture series on entanglement. It covers the material and presents the math in a uniquely intuitive way (Matrix approach).
http://theoreticalminimum.com/courses/quantum-entanglement/2006/fall
and some lecture notes are here...
I agree, but isn't it true that if you limit the system to a simple two particle system where the first is measured and then the second is measured, the second particle will behave just as if it were no longer entangled with the first. (deliberately avoiding entanglement swapping,etc)
When I read this it seemed like what they are describing is 2 photons with the appearance of being bound, not actually bound. Their progress through the medium is controlled by the medium in such a way that they exit together, but then there is no "bound" characteristic other than their...
No. When you measure the first particle, the second is merely no longer entangled. Not entangled does not mean there is no superposition. Don't mix up entanglement and superposition, or connect them in such a way. The second particle still behaves in a QM way the same as any particle...
The former. There is no preferred orientation for the measurement of the first particle, it will always be random, either up or down. After the first measurement the second particle will be the opposite. The math says it works that way, and experiments confirm. Violation of Bell's inequality...
That sentence is confusing for me. Specifically the phrase "the specific quantum state of entanglement was not determined..." If particles are entangled, say for spin, then measuring one of the pair gives you information that the other particle will have complementary spin. That is, the...
I'd rather address this problem as : How does the classical emerge from the quantum mechanical?
One way to approach it is decoherence.
http://www.scribd.com/doc/140961861/Decoherence-Essay-ArXiv-Version
This paper is a good one too:
http://arxiv.org/pdf/quant-ph/0506199.pdf Jump to...
This site gives an enlightning (for me, anyway) view of the math required for physics.
http://superstringtheory.com/math/ Don't forget to go to pages II and III.
Susskind's lecture on entanglement at theortical minimum.com is simplified mathematically and may give you interesting starting...
I'm confused (which is nothing new, BTW, it's one of my hobbies). Maybe we are talking past each other. Let's start with a simple spin entangled system. In a simple entangled two particle system if I measure one particle, it is no longer entangled with the other particle and the other...
I don't understand why you think covering the slit at one end causes decoherence at the other end. At one end the particle goes through 1 slit with no interference pattern. At the other end the partner particle still goes through two slits and interferes. Whether or not there is interference...
I may be connecting two incompatible concepts, but are you simply noticing the pi/4 intersection points of the correlation curves for entangled vs classical systems? Look at the graph on this page.
http://en.wikipedia.org/wiki/Bell%27s_theorem
In a simple system where you measure the first electron and then measure the second electron, the first measurement effectively breaks the entanglement and the second electron behaves simply as an electron with spin opposite the first electron.
In reality it may be more complex than that...
The only thing you can know about the system is that when Bob measures his particle it will correlate with Alice's result. As said previously, Alice measuring does not "cause" anything.
Say she measures in the X axis. She will get + or -. If Bob measures in X he will get the opposite (+...
Maybe I am missing the whole point, but when you measure the first particle you no longer have an entangled system. The second particle is just an electron with a state. You can find out things about it or do tricky experiments or play weird games by knowing the results of the first...
"But, when the polarizer at Dp is put in place its polarization apparently matches one or the other of the quarter wave-place polarizations, "
I don't think so -- it is diagonal.
They are simply using coinicidence detection between the idler and the target to only count entangled pairs. The first experiment could have said, "only measure coincidence detections of entangled pairs", but they just assume you are only measuring entangled pairs. The first is a summary, the...
I think the second explanation is saying the same thing as the first. Place a diagonal polarizer in the path and then record coincident detections. The first explanation just assumed you recorded coincident detections. Coincident detections are just to filter for only entangled pairs. But...
"So shouldn't the shot-out electron be constantly collapsing as it travels towards the slits? But then GRW entails that there can never be interference patterns!"
I think that assumption is broken. There cannot be interference patterns if the "particles" are not in the same state when they...
I don't think anybody is saying it provides data transmission of any kind. Do you understand the game being played, and what constitutes winning? I think it is simply a way to exploit the statistical correlations that are different than classical correlations in order to get a correlation that...
I'm just to the point of beginning to understand the density matrix view so it will be a bit before I can understand what you mean by "it isn't really" (in one of those preferred basis states) and how that is controversial. It seems like that is actually a good thing, in that "fuzziness" hasn't...
Sorry, I missed this post.
Is the mathematics of the effect of decoherence different between a interaction that leaves "accessable" information vs one that is not accessable? I don't see how the encoding of the information changes the significance of the fact that a change in state of the...
I'm not quite sure how to interpret your view "observation should be replaced by decoherence". Do you mean that observation causes decoherence and decoherence means observation has occured, or something else.
If one accepts your view, can one replace the word decoherence with the word...
I think this is an accurate description of how it works. I too have a semantics problem with the "know which path" concept (the word "know" or "identify" has too many connotations). If anything happens that makes the final state from one path different from (orthogonol to) the other then the...
The wikipedia article states "Decoherence occurs when a system interacts with its environment in a thermodynamically irreversible way." Doesn't observation always causes decoherence? Isn't decoherence always caused by some sort of "observation"? Can you say that observation is any interaction...
I don't dispute the theory as outcomes of observations. I'm just quibbling about the words for what constitutes an observation. What thermodynamically irreversible interaction would not constitute an observation? Would not, in fact, leave a mark in your "macro world"?
@KenG -- really, read Bertrand Russell's "The Problems of Philosophy". It gives you a solid framework for the issues you are raising. Totally outside the world of QM.
As for the question I didn't answer, I consider it obvious that it is a question no one has an answer for. I felt the paper...
You need to read some basic philosophy. Try "The problems of philosophy" by Bertrand Russell. It is available on the web. It explains objectivism. What is "real" what can we "know", what "exists" independent of us?
How you can read the Schlosshauer paper and not relate to classical...
I just stumbled across "Experimental motivation and empirical consistency in minimal no-collapse quantum mechanics" .(schlosshauer) http://arxiv.org/pdf/quant-ph/0506199v3.pdf
Puts it all in perspective for me. Doesn't leave much room for hocus-pocus interpretations.