In quantum physics, the no-communication theorem states that it is not possible to transmit information from one observer to another observer, whether entangled or not, by making a measurement of a subsystem of a total state, common to both observers.
Most people think that the theorem is important because it limits quantum entanglement, that separated events cannot be correlated in any way to lead to the possibility of communication.
However, the double-slit experiment [1] says that what one observer does (e.g. turn on a detector) influences what is detected at the other observer (e.g. the electron did not pass here).
What is your reference or position on this question, could the double-slit experiment be used to negate the no-communication theorem?
[1] https://www.researchgate.net/post/Is_it_better_tor_students_to_view_the_double_slit_experiment_as_three_different_cases_or_two?
@ Jacques Lavau At the moment we have a spectacular murder case here in Copenhagen that involves a submarine and tracking its trajectory before it sank is an important component, but I have not heard anybody talking about "a superposed state". Actually I have no idea how your talk about submarines should be relevant to the original question.
The question was whether an observer's decision about the use of a detector may lead to some communication to a (spatially separated) observer via some effect related to entanglement.
These quantum experiments do not contradict the "no-communication theorem". The decision by one observer to turn on a detector does not have an effect at the other observer. It is only the decision to turn on the detector + the observation of detection/non-detection that is correlated with something going on at the second observer and the detection/non-detection is not under control of observer 1. A correlation is established but the correlation is not the result of a causal effect propagating from one observer to the other observer. If the establishment of such a correlation is called communication then it is definitely a communication of a very different nature than what we normally call communication.
You all three live in vaporware, and words-traps.
Entangled representations exist : they are socially accepted ideations. But entangled states do not exist. The socially accepted representation is not a valid descriptor.
Your representations dwell in the newtonian macro-time of the laboratory and the newtonian macro-space of the laboratory. These statistical emergences have no pertinence in microphysics. The newtonian macro-time of the laboratory has no causal power in microphysics, where the waves are individual ones, each with one emitter and one absorber.
Whatever you say about double-split experiments, each photon or each electron travels from one emitter to one absorber, and it never transmutes into something corpuscular. Whatever your expectations and intentions about detectors.
To me a quantum state is a representation of our state of knowledge about the quantum system. If "the socially accepted representation" i.e. our knowledge is not a "valid descriptor", I do not know what would be a valid descriptor.
You and the winners of the Solvay meeting in 1927, came about fifteen milliards years too late to rule that the laws of physics should fit our anthropocentrism, and that the copenhaguist physicist should always place himself in the middle of the microphysical image.
I have summed up the fifteen surrepticious postulates they tought us, in front of the six postulates we have choosen instead.
First version on ResearchGate, and definitive version at , where my english is better corrected.
So we have no more need to censure lots and lots of embarrassing experimental facts, that shoot down the copenhaguist mythology. For instance the Ramsauer-Townsend transparency effect, proved in 1921.
The ambiguity of the word "state" fools the students. When you do not more know where is the submarine, then you state that the submarine "is in a superposed state". You had rather to recognise that your knowledge and the behaviour of a submarine are two different things.
What is the Dirac-de-Broglie noise and what you know about its results (the successful transactions) are two different things.
http://jacques.lavau.deonto-ethique.eu/Physique/15postulates.pdf
Article Fifteen surreptitious, copenhaguist and corpuscularist postu...
@ Jacques Lavau At the moment we have a spectacular murder case here in Copenhagen that involves a submarine and tracking its trajectory before it sank is an important component, but I have not heard anybody talking about "a superposed state". Actually I have no idea how your talk about submarines should be relevant to the original question.
The question was whether an observer's decision about the use of a detector may lead to some communication to a (spatially separated) observer via some effect related to entanglement.
Banesh Hoffmann scribit... the superposed state of the submarine...
If a special emitter must emit a couple of correlated photons, where the polarization of the second is complementary to the polarization of the first, then the transaction is between five partners, instead of the usual three :
One emitter,
two absorbers,
and the spaces and/or optical devices between them, between emitter and each absorber.
The laws of physics are not concerned at all about which of the absorption reactions is the first in the frame of your laboratory, with its newtonian macro-time and newtonian macro-space.
Your macro-time is a statistical emergence, as the entropy is, and has no causal power in microphysics.
However, the double split experiment is an ordinary experiment, where each photon has one emitter and one absorber, and passes through the two or more open slits. An ordinary transaction between three partners, for each photon (or electron if your device is for electrons).
Of course, the calculus and drawings we did in geometrical optics remain valid. What is new is that now we can calculate the width of the Fermat spindles centered on the geometrical rays we had already learned. Where the dephasing of the two ways is an impair multiple of the half period, then the transmittance of the optical device is null (or near so), and no (or nearly no) transaction can succeed. Null or near so (for transmittance) ==> nought or near so (successful transactions).
Hello all,
Thank you for your participation. As you know, Jacques can ask his own question in RG. This question is not that, it's whether an observer's own decision about the use of a detector may lead to communication to another (spatially separated, independent) observer, an observer that is just not "downstream" from the former one -- but it is peer. It's not the place to use words that are unacceptable by a scientific study, but to build, to mine the gold of truth using fair, polite, cogent public discussions.
Jacques, if you do not agree with this, you can continue to observe, or even join in, albeit in fair terms. Otherwise, life itself may become harder, even to all of us, life is a school.
Cheers, Ed Gerck
Ed, you want to stay in your blind alley, so stay in it.
I am trained as a professional finder, you do not have this professional training.
That's all.
"However, the double-slit experiment [1] says that what one observer does (e.g. turn on a detector) influences what is detected at the other observer (e.g. the electron did not pass here)."
May I respectfully correct this statement, adding important missing pieces:
"However, the double-slit experiment [1] says that what one observer does (e.g. turn on a detector) ALLOWS HIM TO INFER what is detected at the other observer (e.g. the electron did not pass here). THIS INFERENCE IS BASED ON THE INFORMATION OBTAINED PRIOR TO THE ACTUAL MEASUREMENT. SUCH INFORMATION IS COMMONLY CALLED, BUT IN GENERAL IS NOT LIMITED TO, 'QUANTUM STATE'."
Hello Plimak,
Yes, "influences what is detected" means "infer" at least part of the actual measurement. It is not a logical deduction, there is plenty of room for error. The inference is, thus, based on what you wrote, and other factors, prior to the actual measurement. I intended to catch all in a succinct form, it may be better for clarity to explicitly cover most of it, as you did. But the actual (surprise?) result is that what one observer does will influence what is detected at the other observer. They should be independent, it seems, from the formalism.
Cheers, Ed Gerck
Hi Gerck,
Observer 2 may infer what observer 1 sees, but observer 1 cannot find out if he is being watched or not. What he sees is independent on whether observer 2 is watching, or dead, or having a fling with his girlfriend. I would rather refrain from calling this influence. The right word is correlation.
@Plimak
It is not influence, so we do not call it influence.
It is not correlation in the usual sense, so we prefer to call it something else.
I propose to do most other scientists do and call it entanglement.
Hello Plimak, Peter, and all,
The term "influence" seems less committal, less biased. It could mean deduct (seems unlikely, but is possible), inference, correlation, entanglement, or something else, or all the above when seen intersubjectively. I preferred to be less committal and ask the RG community, so that is the unbiased question!
On Plimak's point, physics does not care at the moment with consciousness, so it does not matter if observer 2 is actually Alice, a photo detector, or dead, or not. The name should not depend on what we are not accounting for, and there is no model for dead, or fling with his girlfriend, in physics.
On Peter's point, entanglement would imply the negative pregnant question, if observer 1 can see it, why not observer 2? The numbers are arbitrarily named 1 and 2, after all; I could name them othwerwise in reverse order, or use complex numbers (no order possible). If both observers (i and -i) can see it, that could be entanglement as well. There is no preference, no preferred choice. If your reference frame is upside down you might use 1 where I used 2.
Cheers, Ed Gerck
@Harremoës&Gerck
Hi Colleagues,
I would rather stick with "influence" for something that transfers information and "correlation" for everything else. Yes we should distinguish classical correlation that is described within the notion of statistical ensemble, and quantum (EPR or Bell-type) correlation that is not.
As to "entanglement", it is a case rather than the case of quantum correlation. There are tons of others. E.g., antibunching, which correlates measuments in time rather than in space.
Hello all,
Quantum mechanics is not difficult to understand today, we evolved our thinking.
There is not only ONE way something can happen, you can consider ANY path. The theory calculates, by conservation laws, which end-result is obtained, and experimentation confirms.
Take the two-slit experiment, with electrons, here considered. Any path can be followed by the electron, the end-result is calculated, and experiment confirms. You can do it as many times as you like, the end-result is always the same. But you cannot choose or constrain the electron path; the problem is different, the end-result is different.
Cheers, Ed Gerck
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