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Originally posted by Observer99
Originally posted by Jezus
The next level of this experiment is the delayed erasure.
They used the detectors and before looking at the pattern on the back wall (wave or particle pattern) they deleted the information. What they found was that deleting the information after measurement had the same effect as not measuring at all, a wave pattern.
If they keep the information (but don't look at it) it is a particle pattern.
This proves that the measurement does not collapse the wave function but the existence of information does.
Provide a link to this outlandish claim. I'd be very interested if it were true, but right now it's just words on a screen by someone on ATS.
Originally posted by Jezus
The next level of this experiment is the delayed erasure.
They used the detectors and before looking at the pattern on the back wall (wave or particle pattern) they deleted the information. What they found was that deleting the information after measurement had the same effect as not measuring at all, a wave pattern.
If they keep the information (but don't look at it) it is a particle pattern.
This proves that the measurement does not collapse the wave function but the existence of information does.
Originally posted by CLPrime
It's true. ...
We have presented a quantum eraser that uses a Young double slit to create interference...We recovered interference using the entanglement of photons s and p.
We have also investigated this experiment under the conditions of delayed erasure, in which the interfering photon s is detected before photon p. In as much as our experiment did not allow for the observer to choose the polarization angle in the time period after photon s was detected and before detection of p, our results show that a collapse of the wave function due to detection of photon s does not prohibit one from observing the expected results.
So even though these experiments do have some strange and unexpected results, we actually don't see the interference pattern in the total pattern of signal photons at the primary detector. We can only deduce the pattern from a subset of that total. These experiments are done with entangled photons, and we have already shown that entanglement is a strange phenomenon that can allow certain things to happen faster than the speed of light. However, even in these experiments, the information is still not available faster than light:
In the delayed choice quantum eraser discussed here, the pattern exists even if the which-path information is erased shortly after, in time, the signal photons hit the primary detector. However, the interference pattern can only be seen retroactively once the idler photons have already been detected and the experimenter has obtained information about them, with the interference pattern being seen when the experimenter looks at particular subsets of signal photons that were matched with idlers that went to particular detectors.
The total pattern of signal photons at the primary detector never shows interference, so it is not possible to deduce what will happen to the idler photons by observing the signal photons alone, which would open up the possibility of gaining information faster-than-light (since one might deduce this information before there had been time for a message moving at the speed of light to travel from the idler detector to the signal photon detector) or even gaining information about the future (since as noted above, the signal photons may be detected at an earlier time than the idlers), both of which would qualify as violations of causality in physics.
I think you're asking the right questions. I don't have an answer and I'm not sure anybody really does, but I think it might be fair to say that we don't fully understand quantum entanglement yet, and since these experiments involve entangled particles, we have to admit that we don't know exactly what is going on with the entanglement, or what Einstein called "spooky action at a distance". I suspect someday we'll understand entanglement a whole lot better than we do today and when we do, these experimental results with entangled photons will hopefully make more sense to us.
In this case, we must ask, is the particle truly reacting to our observation of the information, or is it reacting to the existence of the information, itself? And, does it react to the destruction of that information, even when the information is destroyed in its future?
Originally posted by traditionaldrummer
The Double Slit Experiment is currently and vigorously being used as the leverage to pass through all manner of new age/metaphysical claims. Although it's a common tactic to use quantum mysteries as a kind of foundation for mystical nonsense I'm unsure why this particular experiment is currently being paraded around with such enthusiasm.
In the case of this thread the DS experiment is used to justify a claim that "we live in a simulation". I'm very skeptical that the experiment indicates any such thing.
I don't know about that. The string theorists who say that may in some cases still be in the physics department, but what I hear them saying is they might get moved to the math department instead of the physics department, unless they can come up with some scientific proof.
Originally posted by Frira
So, physicists tell us the math suggests (or even proves) that at least eleven dimensions exists instead of only four...
Originally posted by CLPrime
In this case, we must ask, is the particle truly reacting to our observation of the information, or is it reacting to the existence of the information, itself?
Originally posted by CLPrime
And, does it react to the destruction of that information, even when the information is destroyed in its future?
Originally posted by Arbitrageur
There's nothing wrong with the math. It's the lack of experimental verification that's the problem.
Originally posted by CLPrime
String Theory is pure math, with very little, if any, testable physics.
Originally posted by CLPrime
reply to post by Frira
Math is great. I love math, too. But, math is not physics. There might be several ways to mathematically describe the universe, but, if none of them can be physically tested or applied, then what good are they?
That's the problem with String Theory. It's all bones, no meat. Until we perfect inter-dimensional travel, it's got no testable hypotheses or practical applications.
Now, the double-slit experiment. I mentioned earlier that the condition-specific wave-particle duality idea, itself, is a little outdated. Here's what the current picture of wave-particle duality is:
All particles are formless, point-like regions described solely by a set of quantum numbers and other intrinsic properties (like charge and energy/mass). They behave probabilistically, so their location at any given instant is defined only by how "probable" it is that the particle is located there. This can be seen most clearly in electron probability clouds, which define the most likely location for an electron "orbiting" the nucleus of an atom. They don't move in predictable ways - one instant, they could be on one side of the atom, while, the next instant, they could appear on the other. All we can truly say is how "probable" it is for the electron to be at any given location.
And this applies to all particles. Even photons travelling in a straight line. In this case, however, the probability forms a wave through space, and the result is that the photon appears to travel in a wave-like manner, when, in fact, it is travelling "straight" through a wave-shaped probability cloud (like ripples on a pond, where the crests represent regions where the photon is most likely to be, and the troughs represent regions where the photon is least likely to be). This wave-shaped probability cloud is called the wave-function.
In the double-slit experiment, it is the wave-function which interferes with itself when passing through the slits, and the photons are then bound to follow this interference pattern.
All these experiments do, then, is destroy and/or restore the wave-function, which is different than destroying and/or restoring the photon's own interference pattern.
Originally posted by CLPrime
reply to post by Frira
Of course, the idea here is that a photon (and every other particle) is a wave and a particle at the same time. Though, the term "particle" is a little misleading. It used to be a physical object. Now, it's just point in space having spin, charge, and mass. And the location of this point in space at any given time is defined by the wave-function.
Personally, I think we'd be having better luck coming up with working quantum theories if we started thinking of the wave-function as what's real and not the particle, itself. Both exist, but the particle is merely information contained at a point in space... the wave function defines the physical existence/location and motion of that information.
In general, I'm quite open to the possibility of a limited anthropocentric universe (in fact, my life is based on belief in such a universe), but we need to be careful if we're going to try to use physics (especially quantum mechanics) to prove such a concept.edit on 22-6-2011 by CLPrime because: (no reason given)
Originally posted by tetsuo
Free will...
Originally posted by Frira
I also suspect a primary misconception I am holding is that the wave properties are of the thing. I suppose the reality is that wave refers to an artifact of the effect of the thing upon space. But I cannot reconcile that to the experiment except to say I prefer the idea that space was effected by the measurement rather than the photon. Now that I think about it-- that works a lot better with the erasure phenomenon as well.