Thought Provoker
Posts: 530
Joined: April 2007
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Hi olegt,
Ok, I will concede the Afshar experiment lacks support of Penrose's OR (at least until I understand it better).
And since you seem to be more comfortable with me quoting Penrose I will do that after a minor side trip.
I sense something that is on the fringes of "standard QM". That is whether or not there is a common agreement on the existence of a hard threshold for coherence/decoherence.
From the Penrose co-authored paper Towards quantum superpositions of a mirror
| Quote | | In 1935 Schrodinger pointed out that according to quantum mechanics even macroscopic systems can be in superposition states [1]. |
With the citation...
"[1] E. Schrodinger, Die Naturwissenschaften 23, 807 (1935)."
During the Hawking/Penrose debate, Hawking seem to imply no hard decoherence threshold but, instead, referred to various environmental effects causing the collapse in the Schrödinger's Cat situation.
Here is what is said by BuckyBall experimenters in a paper titled Quantum interference experiments with large molecules
| Quote | B. Coherence and which-path information
We might believe that coherence experiments could be spoiled by transitions between the many thermally excited states. Obviously, this is not the case, as has been shown by our experiments. But why is this so? No matter what we do, we can only observe one of these qualities in its ideal form at any given time. If we tried to locate the particle during its passage through one of the two slits, say by blocking one of the openings, the interference pattern would disappear. This rule still holds if we do not block the slit, but manage to obtain which-path information for example via photons scattered or emitted by the molecules. Sufficiently complex molecules, in contrast to the electrons, neutrons, and atoms used so far, may actually emit radiation41,42 without any external excitation, because they have stored enough thermal energy when leaving the oven. According to Bohr’s rule, the interference pattern must then disappear if the molecules emit a photon with a sufficiently short wavelength which enables the experimenter to measure the location of the emitting molecule with sufficient precision. According to Abbe's theory of the microscope, the photon should have a wavelength shorter than twice the distance between the two slits.
What actually saves the experiment is the weakness of the interaction. The wavelength of the most probably emitted photons is about a factor of 100 larger than the separation between two neighboring slits. And the number of light quanta that actually leak into the environment is still sufficiently small—of the order of one, up to potentially a few photons—and cannot disturb the interference measurably. Therefore, even if the fullerene molecule emits a few photons on its path from the source to the detector, these photons cannot yet be used to determine the path taken by the molecule. In other words, the photon state and the molecule state
are not, or only very slightly, entangled because the two possible photon emission states from either path largely overlap. In a sense we may say that the fullerene has no ‘‘memory’’ along which path the emission occurred |
Is this the standard QM explanation?
Let's hear from Penrose starting on page 851 from The Road to Reality...
| Quote |
[The uncertainty of separated mass] directly leads, via Schrödinger's equation, to an absolute uncertainty E in the energy of the superposed states under consideration. The next step is to convert this expression for E into another (equivalent) mathematical form, which we can interpret as:
E = gravitational self-energy of the difference between the two mass distributions in the states |x> and |q>.
...
So what are we to do with our fundamental 'energy uncertainty' E? The next step is to invoke a form of Heisenberg's uncertainty principle... [where] the average lifetime T having an inbuilt time uncertainty, is reciprocally related to an energy incertainty, given by h/2T. ... According to this picture, any superposition like |Y> would therefore decay into one or the other constituent states, |x> or |q>, in an average timescale of
T = h/E
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Which means that massive objects do not stay in superposition as long as less massive objects.
olegt, at this point I'm not sure where our disagreements are. You confirmed my understanding of the Traveling Twin's shorter path through spacetime. While you balked at my use of quantum information, you appeared comfortable with Penrose's quanglement. I didn't get into the single wavefunction because it was obvious you would view that as just philosophical shading of standard QM like TIQM.
So now, I am expecting you to say something about Penrose's OR hypothesis needing experimental support.
I will respond to that after you do so.
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