Neil,

Your very interesting essay deals with photon polarization. I have a question that no one ever asks: Can a single photon really be anything other than circularly polarized, with spin +/-1? In my view, all fundamental particles are rotating vector fields with quantized spin. (See my essay "Watching the Clock: Quantum Rotation and Relative Times", esp. Endnote 2.) And indeed, all atomic transitions involving photon absorption or emission transfer this amount of angular momentum. This question is important because virtually all quantum optical experiments establishing quantum entanglement involve measurements of linearly polarized single photons. If instead, a linearly polarized state must be the superposition of two circularly polarized photons, then the entire block of evidence for quantum non-locality is in question. Any thoughts on the subject?

Alan

Thanks, Alan, I will look at your essay. Yes, photons can be considered superpositions of R and L circular states - yet theory says we always "find" a photon as having either () or (-) spin (hbar or -hbar, sorry don't have time to hash out LaTeX here.) Yes, it makes sense for a photon from an atomic transition to be circular. Yet we can pass it through a linear filter and prove that the output (if it survives) is a superposition and not a circular state. I don't think non-locality is in question since the correlations of entanglement still can't be explained non-locally (more precisely, can't involve forbidden combinations of locality and realism.) The correlation of circular polarization is indeed not a true proof of NL, since it's a simple binary correspondence to satisfy conservation.

However, I presented reason to believe that the concept of straightforward manifestation of spin is an over-simplification. Detection of a linear state by filtering (especially if very indirectly) does not logically require actual change of the expectation value of AM of the system. I think that change in an intervening element like a HWP is even less credible.

The detailed argument is in the essay, yet for a start consider the asymmetry of the reverse process: would we really expect circular states detected "as linear" (say by filters or calcite analyzers) to *not* transfer their angular momentum? And if they did, then I repeat from my essay: "Yet why should linear detected "as circular" prompt change in angular momentum, yet circular detected "as linear" continue to exert the effects of circular?" If my hypothesis is correct, then a UO could indeed distinguish between a mixture of R,L versus a mixture of H, V - although it would require waiting for very rare runs of apparent R or L detections for the H, V mixture.

Neil

"In this author's view, being unable in principle to find out everything about the world's contents implies that "bit" (information) is derivative and subsidiary to "it" (real objects.)".

Logically (ie in principle) we could find out everything, because what we can know (which is the equivalent of physical existence) is limited by the physical process which enables knowing. Though in practice I doubt we will ever achieve it, but that is a different point. I presume your statement is not an allusion to all the possible alternatives that might exist, but we can never know, as that involves belief, not science. However, that is not what causes 'bit' to be derivative. Information is information because it is representational of something else. It can be an it (ie real object), of itself. For example, light, vibration, noise, etc. And then one has to establish the extent to which it is valid information (more commonly known as knowledge), ie corresponds with physical existence, as invalid information is useless.

In respect of observation, the more pertinent question is what has observation (informed or otherwise) got to do with it. Observation (measurement) is a process which involves the receipt of physical input (eg a photon based representation of what occurred) which is converted into a perception of that input. So observation, or indeed any form of sensing, has no effect whatsoever on the physical circumstance. Other than, somewhat obviously, the input ceases to exist in that physical form as a result of that interaction. But then that occurs if the light had interacted with a brick instead. The only difference being a brick does not have the capability to process the input receivable. Observation cannot affect physical circumstance because the sequence order precludes it (ie the input is received, it already existed before the subsequent processing), and that processing is not a physical process, it does not involve an alteration in physical form. Apart from the simple fact that what is received is not the existential sequence (commonly known as reality) anyway, but a physically existent representation of it. So there is no interaction in observation between the observer and reality.

Put simply(!), whatever reality constitutes, it is physically independent of the mechanisms whereby it is detected. So why do we have a physical theory purporting to explain physical circumstance, where observation seems to be integral to existence, as opposed to just being the mechanism whereby we find out what happened?

Paul

    Jochen

    More precisely, just what have observers got to do with it (see my post below).

    Re information, as per your last post to me, this notion of designating everything as information is pointless. Everything provides us with information. And we can only have information, because we cannot 'directly access' reality. But unless some proper differentiation is invoked then the label 'information' becomes meaningless.

    Paul

    Paul, you would need to study more quantum mechanics to see how important observation is. I can't really summarize how that works out, but my article attempts to show that we can at least find out more than standard theory posits. Note that even if you say "the reality" would be there anyway", we still need a way to find out what that is. To some extent you have been vindicated, in that "interaction-free measurements" are now appreciated and used.

    • [deleted]

    • Post #11

    Why cannot we ' directly access' reality by oprning our eyes?

    • [deleted]

    • Post #12

    As probably the most uninformed observer likely to read your essay could I please point out to you that a light is a light is a light. Light does not consist of invisible photons, klingons, croutons or carryons that can or cannot behave in positive or negative unpredictable ways. Man made particles have nothing to do with reality. Only unique real snowflakes occur. All fabricated particles have to be unique. Why cannot you understand that if nature only produces unique states, men could only produce unique states? There is only one of anything, once. There is no such thing as real scientific information. There is no such thing as real layman information. All information is abstract and has nothing to do with reality because only unique real events take place that cannot be deciphered by any abstract code.

      Joe

      Because the physical input you receive is light, and that is not the reality, it is a physically existent representation thereof. It was created as a result of an interaction with it, and light has features which make it good at representing. Hence the evolution of sight. If light was just random, or bizarre, then sight would not have rendered the possessor an advantage, ie he would not have seen the big monster coming and been eaten anyway!

      Precisely how good light is as an accurate and comprehensive representation of what occurred is a question concerning the physical properties of light, how it intereacts and how it conveys, and what influences it i susceptible to whilst travelling.

      Paul

      Neil

      It is not a matter of how important observation is, in order to discern what occurred, but that that process cannot affect the physical circumstance.

      Paul

      Neil

      This is difficult to follow in this format.

      Very early on there is a false statement, ie any two events with the same properties are identical. If they are two then they cannot be identical!! The properties, whatever that relates to, are the same. But I doubt very much anyway if an exact same set of circumstances could re-occur. This smacks of similarities being drawn at a level of conception that is higher than what actually exists. So as a methodology for categorisation, then ok, but not as a depiction/explanation of physical existence.

      And physical existence is not a series of events, it is a sequence of physically existent states. And within any given stateh there can be no form of change, otherwise it cannot exist. This is the only route out of the conundrum that existence involves existing but also difference. It therefore has to be a sequence of discrete states. That is why he then confuses time and timing. Time is not a succession of moments, that is the timing system. Time is the rate at which alteration occurs in realities.

      Paul

      Paul, Joe: I can't blame you for wanting to apply philosophical intuitions and deduction thereof to what you think the universe is like, but our intuitions are often wrong. Science is above all about "finding out" through often deep and difficult experiments, rather than working out what reality must be like through basic practical observations and reflection. We live in an unexpected universe. I still appreciate your interest.

        Neil

        There is nothing philosophical about what I am saying, or indeed what Joe has just said. They are generic statements, ie facts devoid of the detailed form. See the wood for the trees is the expression.

        And hasn't it ever struck you that the substantiation of some science as being counter intuitive rings an alarm bell?

        Science is not about "finding out", if the start premise is wrong, ie does not correspond with how physical existence must occur. Like for instance, asserting that the activity of observation has an affect on the physical circumstance, asserting that existence occurs relatively, asserting that there is time in a physical reality, not differentiating the existential sequence from the existential representation thereof (eg light), not understanding that physical existence can only occur in one definitive physically existent state at a time, etc, etc.

        Paul

        Joe

        Your essential point is correct. Physical existence comprises a sequence of discrete, definitive, physically existent states. We know there is existence, and that that involves difference. And the only way out of that conundrum is sequence. Of course one can invoke all sorts of beliefs, but this is supposed to be science. And we can only have knowledge of what occurred (this is another answer to your question above about opening our eyes.

        But, because we are in an existentially closed system (we only know because of a physical process), what we do know can be validated, albeit within that confine and then ultimately we can deem that knowledge to be the equivalent of the physical existence knowable to us. In simple language, we know all there is to know.

        Paul

        Neil, I just finished reading your very interesting and well thought out essay. You argue that "it from bit" is impossible because we cannot know all information about a state. Is "it from qubit" or "quit from qubit" possible?

        And light creates all real odors, sounds, tastes and tactile impressions. Who knew?

        Philip, thanks. True, I think that "it" is in some sense "greater" than "bit" because we can't know everything about the universe - in particular, quantum states. There is also an asymmetry between observers of different degrees of "in the know." For example, Alice the PO can create a qubit of a certain polarization aR beta L. It is known to her and anyone she wants to tell, which can be demonstrated by certainty of match testing. To that extent, an undisturbed qubit is fully actualized by the information characterizing it. [Note: I gave up on symbols etc. in these comment boxes, it doesn't correspond to the simple rules I expected.] But Bob, a UO who doesn't know what this state is, must guess by applying simple binary tests which destroy the information.

        Note however that once the qubit escapes and begins being buffeted and distorted by the environment, Alice can lose control of her inside information and even she is not able to know for sure the nature of the qubit. (Note: I don't think this process in any way explains collapse of the wave function or definite outcomes, see my first FQXi essay.) My own techniques might allow Bob to find more about that one photon, or distinguish mixtures previously considered equivalent, but the fullness of the universe's events is still going to be beyond the reach of either Alice or Bob. Hence the universe is indeed to some extent "acataleptic" in a general sense. It is more than *anyone's* information. I am only helping to democratize between relative levels of privilege.

        I agree with the asterisked part of this Smolin quote from the reference above:

        "The most radical suggestion arising from this direction of thought is the insistence on the reality of the present moment and, beyond that, the principle that all that is real is so in the present moment. To the extent that this is a fruitful idea, *physics can no longer be understood as the search for a precisely identical mathematical double of the universe. That dream must be seen now as a metaphysical fantasy that may have inspired generations of theorists but is now blocking the path to further progress.* Mathematics will continue to be a handmaiden to science, but she can no longer be the Queen."

        PS - Not sure re "quit" - typo or neologism?

          interesting point about the mathematical double. Smolin confuses the issue by talking about things like evolution that cannot be well explained in mathematical terms. There are indeed many parts of science that are not served well by mathematics and there may be more of that in physics than people expect. E.g. I think people have had too high an expectation that low energy physics of standard model can be derived from a fundamental theory. On that much I agree with Smolin.

          However I dont yet see a reason to abandon the idea that the underlying laws of physics are described by some yet to be discovered mathematical formalism, even if some things depend on the solution of the equations rather than the equations themselves. The effectiveness of maths in physics points in that direction and it seems to me that the only alternative is to allow an element of the supernatural in which case science is really doomed. I would be interested if anyone can see it another way.

          In his book Smolin talks about "metalaws" and a principle of universality that may explain them. This is so similar to my ideas that I wonder if he got that from me. It is not clear if he accepts that at this level of metalaws the mathematical principle holds.

          Hmmm. Well, I wouldn't say the trans-mathematical nature has to be imagined as "supernatural", just "non-realist" - not the sort of realism we expect. We already have the oddity of random muon decay (supposedly identical "structureless particles" with differing lifetimes, which is an absurdity in deterministic terms. Quantum randomness in general can be described en masse but the individual events cannot be predicted in principle. I don't accept MWI or the guise of "continued Schroedinger evolution," so that is genuine randomness. MAth functions cannot create literal randomness since their results are bound by logical necessity. We must use seeds in pseudorandom generators etc.

          Philip, Neil - in relation to Smolin, determinism, math and computability:

          According to Lee Smolin (and his Loop Quantum Gravity) self-organized critical systems are statistical systems that naturally evolve without fine tuning to critical states in which correlation functions are scale invariant (Ansari H.M., Smolin L. Self-organized criticality in quantum gravity. arXiv:hep-th/0412307v5).

          I would support the view of Smolin in the meaning that the universe is a dissipative coupled system that exhibits self-organized criticality. This structured criticality is a property of complex systems where small events may trigger larger events. This is a kind of chaos where the general behavior of the system can be modeled on one scale while smaller- and larger-scale behaviors remain unpredictable. The simple and well known example of that phenomenon is a pile of sand.

          When QM and GR are computable and deterministic, the Universe evolution (as naturally evolving self-organized critical system) is non-computable and non-deterministic. It does not mean that computability and determinism are related. Roger Penrose proves that computability and determinism are different things (Penrose R. The Large, the Small and the Human Mind. Cambridge University Press, 1997. p.120).

          To summarize my view: the actual Universe is computable (however only in Lyapunov time) but its evolution is non-computable.