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Is quantum mechanics a complete theory of nature? 
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#37
Mar1812, 03:30 PM

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At first that means they only talk about SPDC processes and completely ignore single photon sources which have been realized are definitely not amplified squeezed vacuum. Second, the similarity between SPDC and amplification of some vacuum modes of the em field is well known. Pretty much any spontaneous emission process can be understood as amplification of a vacuum mode. All in all the important point is that their claim of "Planckclassicality" being more important than the standard Glauber definition is not tenable. Apart from that the explanation that any SPDC process creates a field with a positive Wigner density is not tenable at all. See e.g. "Amplification of Quantum Entanglement" by De Martini (PRL 81, 2842–2845 (1998)) for a sketch of how the Wigner function of such a state actually looks like. Add the arguments Zonde presented and it becomes clear that the proposal of Marshall and Santos is just not in accordance with what actually happens. 


#38
Mar2112, 11:51 PM

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#39
Mar2312, 12:47 AM

PF Gold
P: 1,376

About other things  we do not need theory of everything to make testable statements. Strictly speaking all our theories about physics are incomplete. It's that scientific method does not allow conclusive proof of a theory. 


#40
Mar2312, 02:26 AM

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Is quantum mechanics a complete theory of nature? No.



#41
Mar2312, 12:05 PM

PF Gold
P: 1,376

Considering that there is no complete theories of physics in a sense that they give conclusive statements maybe it's more sense to talk about completeness or incompleteness of QM as consistency or inconsistency of theory.
I suppose that was the sense how Einstein was talking about incompleteness of QM  that different representations of the same physical situation within the theory are not in conflict with each other. 


#42
Mar2312, 06:06 PM

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#43
Mar2412, 10:48 AM

PF Gold
P: 1,376

There is nice letter where Einstein tries to explain his position  Einstein's Reply to Criticisms From there: This gives quite different picture than the one you are drawing. It's not about lack of another theory but about lack of metaphysical core for the theory that we could call model of reality. 


#44
Mar2512, 08:29 PM

P: 59

The Bell theorem is a mathematical rule describing the behavior of a mathematical model (the photon) in order to define a physical concept (locality). In order for qm to be consistent a physical model is needed to define a physical concept. 


#45
Mar2612, 01:51 AM

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#46
Mar2612, 04:55 AM

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#47
Mar2612, 05:17 AM

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#48
Mar2812, 09:18 AM

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#49
Mar2812, 09:53 AM

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#50
Mar3012, 04:57 AM

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#51
Mar3012, 05:03 AM

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#52
Apr112, 10:57 PM

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1. Taylor calculated photon number by comparing it with average light intensity, however the fluctuation of photon density in the light beam is and always will be unknown because detectors are not perfect recording devices. 2. Photographic emulsions depend on the developability of silver bromide crystals to record the arrival of photons. This occurs in two stages lasting approximately 106 sec, and is characterized by the ejection of an electron and subsequent neutralization of a silver atom. ( C.E.K.Mees & T.H. James, The Theory of the Photographic Process, (MacMillan, NY), 1966.) The chemical properties of the crystals together with quantum efficiency of film have been used to calculate the estimated number of photons required to develop a silver halide crystal and found to be approximately 100 photons. (P. Kowaliski, Applied Photographic Theory (Wiley, NY), 1972.) Taylor did not know this so his experiment is flawed. 3. A more recent study has found no interference fringes even after 336 hours of exposure with a photodetector, a finding which directly contradicts the idea that a photon interferes only with itself. (E. Panarella (1986). "Quantum uncertainties", in W.M. Honig, D.W. Kraft, & E. Panarella (Eds.) Quantum Uncertainties: Recent and Future Experiments and Interpretations, (p. 105) New York: Plenum Press.) If Loudon is unaware of these properties of film then how do I know that the photodetection process was properly analyzed? I have found no analysis of its physical properties in his book. The correct interpretation of antibunching and other quantum optical experiments is based on the physical nature of detections and is therefore suspect unless these questions can be resolved. 


#53
Apr112, 11:36 PM

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nortonian, rather than getting bogged down in the weeds of how we know a photon detection is really a photon detection, let me ask you this. The proof in the Herbert link I gave you just involves correlations of detector clicks, whatever is causing those clicks. The point of the proof is that no local hidden variable theory can explain the correlations of detector clicks predicted by QM. Do you agree with this conclusion?



#54
Apr212, 02:12 AM

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