Comments by "Lepi Doptera" (@lepidoptera9337) on "Why is quantum mechanics non-local? (I wish someone had told me this 20 years ago.)" video.

  1. The universe is 100% local. It is also 100% real. :-)
    2
  2. Bell wasn't wrong wrong. He made a non-relativistic derivation about a phenomenon that follows trivially from relativity. If you read his actual paper, you will find a few sentences at the end where he makes exactly that remark. He already knew that his paper was useless because there was a much, much tighter bound on these correlations, which happens to be exactly what standard quantum mechanics predicts. The universe is either relativistic and then Bell is unnecessary or it's not relativistic. The latter does, of course, have catastrophic consequences for everything else in physics.
    2
  3. Yes, that's complete bullshit. ;-)
    2
  4. Yes, but you have to spread them out over the entire universe. In essence you will arrive at a complicated version of superdeterminism, if I am not mistaken.
    2
  5. Yes, because it is completely wrong. ;-)
    2
  6. No. Gravity propagates at the speed of light.
    2
  7. Bell is right. He was especially right at the end of his article that nobody seems to read. ;-)
    2
  8. Yes, that's also complete bullshit. ;-)
    2
  9. Superposition doesn't have a physical reality, it's just a mathematical property of the theory. What does have a physical reality is that qbits don't have any state at all until measured. It is NOT true that they have a classical state that just hasn't been revealed, yet. This is nothing special, by the way. Dice have the same property. Dice have a well defined state in the set of outcome states only while they are resting on the table. As soon as we are giving them non-zero kinetic energy in the rest system of the table their motion can not be described with one of the six outcome states anymore. So even dice don't have a state while they are still rolling. The situation gets worse in quantum mechanics because quantum mechanical systems are relativistic and their future depends on physics that in the present is happening in spacelike separated regions of spacetime. That physics is simply not defined in the here and now.
    2
  10. Non-locality has never been observed. Does that stop anybody from talking about it in a religious setting? No, of course not. ;-)
    1
  11. Superdeterminism is bullshit. ;-)
    1
  12. There can be no non-locality. Non-locality automatically violates relativity. The main ontological problem here is that wave functions are not even physical properties. Most people, many quantum mystics included, don't seem to realize that.
    1
  13.  @Morberticus  Yes, what people call non-locality is non-separability of certain states. Non-locality simply doesn't exist, non-separability is an absolute necessity. One can't satisfy any of the conservation laws without it. It is only subtle for people who never got further than their first introductory quantum mechanics class into the subject. Everybody else will recognize this to be part of the trivial preliminaries to real physics.
    1
  14. What is spooky about YOU building a machine that can only measure A, B and C but not D and then D never coming out of the machine? :-)
    1
  15.  @marcozec5019  One has to understand measurement as a real, hands on, expensive lab hardware kind of process. It is not some "esoterical, mathematical, philosophical" abstract. A typical quantum mechanical measurement apparatus is like a spectrometer, which consists of an aperture/grating system that separates different wavelengths of light, followed by a detector, which could be a photodiode, a CCD camera, a photomultiplier tube or just the unaided human eye. It turns out that we can build many different kinds of spectrometers of this kind, that select different properties of the light. The most simple grating is a single slit, which detects if light is coming through one particular spatial region. The next kind is a lens followed by a single slit, which detects if light is coming from a certain direction. The first kind of measurement is a position measurement, the lens makes it a momentum measurement. With an input slit and a fine physical grating we arrive at a true spectrometer that measures the energy distribution in the incoming light. We can add a "temporal aperture" and then get time dependent distributions as well. What never changes is the actual detector, which always removes energy from the electromagnetic field. What the math of the theory describes (in an abstract way) is the particular physical effect of our physical apertures/lenses/gratings etc.. This is almost never mentioned in theory textbooks. For that you have to study experimental physics textbooks which explain "how" a particular measurement can be done with actual physical means. There is, unfortunately, no trivial correspondence between experimental hardware and the operator calculus that we can find in theory books. There simply can't be because there are no "ideal" experiments. A quantum mechanical "measurement operator" can, at most, be crudely approximated with actual lab hardware and there is a lot of art and hard work to that experimental process. Most of the "fundamental problems" in quantum mechanics stem from the different kinds of approximations that we have to make to get from real hardware to the operator calculus. They exist in the theory but they don't exist in reality because the limits of the theory that cause the perceived problems are being made obsolete by the actual physical processes that are happening in an actual measurement. One can learn some fundamental insight from that, as well, but they are usually lost in the theoretical literature which suffers a little bit from naval gazing. If all you do all day long is to look at the structure of the ideal theory, all you will ever find are the problems with the theory, whether they are actually present in reality or not. Most of them are not.
    1
  16. It doesn't do anything for you because it doesn't expose any important phenomena that can not be understood more easily on other systems.
    1
  17. You don't have to believe that. Non-locality automatically violates relativity but no such violations have ever been found. Locality is one of the hardest facts in science.
    1
  18. Actually, it takes no time at all to travel between stars. What such travel does, though, is to prevent us from returning to our own present (or near future). We can only return to our own far future. If that is a concern to you, then just don't travel. If you don't care, then there is no fundamental problem with going anywhere in the Milky Way. The technological problems will be solved within a century or so.
    1
  19. Yes, it was always just correlation. Nothing to see here. There never was. ;-)
    1
  20. No, that's not how it works. For starters you don't have particles. You have systems that do or do not have quanta of energy. In case of an entangled photon pair the system is the physical vacuum and there are two quanta worth of energy in there. There is no difference between the two. To nature they are completely indistinguishable. So if one of these quanta get measured, i.e. the energy gets removed from the field, the there is one more quantum of energy left. Because of angular momentum conservation the total angular momentum of those two quanta has to add up to zero, which causes a correlation between the two measurements.
    1
  21. I should probably give you some attention, then. ;-)
    1
  22. There are no particles and you aren't flipping any non-existing particles. If people would pay better attention in school when we explain to them that "quanta are small amounts of energy", then there would be way less confusion.
    1
  23. You are talking to a wall. Quantum mystics like Sabine don't understand the phenomenology. ;-)
    1
  24. So you were simply not paying attention in school. :-)
    1
  25. Imagination doesn't get you very far in science. It usually gets you an F. Like... right now. ;-)
    1
  26.  @zidaneabderahim7131  You have to pay attention in school and then go into the lab a couple times. At least. More lab is better. :-)
    1
  27.  @zidaneabderahim7131  Physics isn't theory. Physics is experiments like those at CERN. If theory would work, then the Greek philosophers would have solved the problem a long time ago. They didn't. That you don't understand what the SE does is because you haven't been in the lab. I have talked to plenty of real, very gifted theoretical physicists who didn't understand it and you are definitely not even one of those.
    1
  28.  @zidaneabderahim7131  If theory would work, then the Greek philosophers would have solved this a long time ago. They didn't. That's why we need experimental facilities like CERN. What you said about this is total nonsense. Please try to educate yourself. I can't do that for you. That is YOUR responsibility.
    1
  29. Yeah, physicists are considering none of that. ;-)
    1
  30. The spin projection we measure is the only spin projection there is. The system doesn't have a spin projection before the measurement takes place.
    1
  31.  @atklm1  Let me repeat this, again. There is no spin projection before the measurement. The only "reality" in quantum mechanics is the reality created by measurements. That is no different from classical mechanics, by the way, except that there it doesn't matter if we pretend that things that have never been seen "exist" or not. That logical error has no lasting consequences in classical mechanics. In quantum mechanics it leads to contradictions. The result of a measurement is NOT random. We know what happens when we introduce random variables in physical systems: they create dissipative phenomena and they destroy energy and momentum conservation. None of that happens in quantum systems, which means that it can NOT be random. The result of a measurement is instead correlated (entangled) with the state of the measurement system. We can not know precisely what that state is because that would require another measurement and so forth ad infinitum. The microscopic explanation for why this can't be any other way can be found in relativity: every quantum system is entangled with the future, which means that the "local, present state" is necessarily uncertain unless all of the future is known. I think we have plenty of evidence that the future is not knowable.
    1
  32.  @Thomas-gk42  It wasn't my laboratory. CERN belongs to the EU and the US national labs that I worked for belong to the US government. Not let me give you some more attention. You are clearly lonely. ;-)
    1
  33. There is no measurement independence. Quantum mechanics explains in detail how the outcomes have to depend on the kind of measurement we are performing.
    1
  34.  @Thomas-gk42  Only to those who don't understand physics. ;-)
    1
  35.  @Thomas-gk42  Let me give you some more attention. :-)
    1
  36. Both. ;-)
    1
  37. Photons don't pass these filters, at all. A photon is a small amount of energy that an external system emits into or absorbs from the electromagnetic field. So if the filter does not absorb any energy, then there is no photon to speak about. If it does absorb a photon's worth of energy, then that energy is gone from the field, i.e. it does not "go through". Part of the problem with quantum mechanics is that most explanations do not contain this aspect of quanta but they treat them as if they were classical objects, which exist independently of their detection. That, however, is not what quanta are.
    1
  38. That sounded like total nonsense. I have generated many individual photons. ;-)
    1
  39. There is nothing to verify. All of physics is perfectly local. You can find it in every introductory chapter of virtually every quantum field theory book. If the world was not local, then your iPhone would have an ansible, but on the downside the universe would not exist. ;-)
    1
  40. That's the difference between probability theory (it has a linear measure) and quantum mechanics (with a quadratic measure). We aren't looking for objects at all here. Quanta are small amounts of energy. Energy doesn't behave like an object, not even in classical physics.
    1
  41. ​ @rossholst5315  What are you trying to do? Model a classical system like a falling ball with quantum mechanics? For that you have to solve the SE for that potential, then approximate your object with something like a very narrow Gaussian at some point in the potential and then solve the time evolution for that potential. Can be done, has been done (e.g. for particle in a box systems, linear harmonic oscillators, gravitational potentials, the Kepler problem etc..). The classical dynamics can be recovered to some extent for the case of very large quantum numbers. The wave function of that solution will oscillate extremely rapidly because n is so high and the classical solution is basically the result of averaging around these rapid oscillations. This is not how nature creates reality, though. That happens through continuous weak measurement. The relevant search term is "Mott Problem".
    1
  42.  @rossholst5315  A simple quantum system doesn't oscillate at all. It exchanges energy irreversibly with its environment. What oscillates is the quantum mechanical ensemble of the system, if we go to high enough excitations, and a large number of coupled quantum systems like a laser. Oscillation is an emergent phenomenon. The mental model that photons are passing the filters is simply wrong. There are no photons in the free field. Photons are the irreversible energy exchanges at source and detector. Copenhagen makes this completely obvious, most people are simply not paying attention to its structure.
    1
  43.  @rossholst5315  How much energy passes through these filters can be predicted perfectly fine with Maxwell's equations. There is no quantum mechanics here. There are only tons of people who don't understand physics. :-)
    1
  44.  @rossholst5315  If you want to understand this, then the best place is in the lab. Once you experience the "clicks" of a quantum detector, quantum mechanics will become a lot more obvious. :-)
    1
  45. About what? Entanglement? You can probably read up on entangled states in most newer textbooks on quantum mechanics. Whether it will help you to understand... that I am not sure about. Most textbooks will give you the math but none of the physics that you need to understand these phenomena.
    1
  46. I don't know what books you are reading, but in actual quantum mechanics textbooks quantum mechanics is fully local but there are non-separable states. The locality is needed to satisfy special relativity and the non-separability is caused by special relativity in return. Anybody who tells you differently is simply lying to you. You are welcome to go to the library and read the books yourself.
    1
  47. They are no more causally connected than the envelopes in the classical example. What trips us off is that we assume that systems are in a specific state at all times. That's just not so. Imagine having two dice. One only has sides with even numbers. The other one has sides with odd numbers only. Separate them randomly and send them far apart just like the envelopes. Did either of the two dice have a definitive face value during shipping? No. Will there be a correlation between outcomes once both receivers start throwing them? Yes, because we can still tell that the other person received the even numbered one if we throw ours just once and get an odd number as outcome.
    1
  48. The wave function never collapses. The wave function is a description of an infinite number of repetitions of the same experiment. It says absolutely nothing about an individual experiment. Your argument with light cones is the correct way of looking at it. The two measurements in this system can have spacelike separation, in which case they can't have a causal connection (some observers will see A before B and others will see B before A). That is all there is to it. Relativity rules out any other solution.
    1
  49. What's up with the SEO bots today? ;-)
    1
  50. @ Your post didn't have any meaningful content, which is typical for SEO bot postings. ;-)
    1
  51. @ Nobody can. That is very typical of SEO bot postings. They are made with a random text generator. ;-)
    1
  52. Because of angular momentum conservation.
    1
  53. @ The total angular momentum is conserved. This includes the angular momenta of the measurement systems. People who talk about entanglement all day long usually forget that the measurement systems also have to be included. So, no, if you just look at the measured angular momenta (or, better, the spin projections), then it's not even conserved because for two measurement systems that have their projection axes rotated by 90 degrees the correlation between the measured spin projections is zero. However, if you were to measure the total angular momentum of the two measurement systems AFTER the measurements, then you would find the total unchanged, even if the measurement results seem to contradict that.
    1
  54. There are no hidden variables. Both you and Einstein could have seen this immediately in an ordinary spacetime diagram, but neither of you took the time to think about this thoroughly.
    1
  55. So you are telling us that you are an expert in bullshit? I doubt even that. ;-)
    1
  56.  @Thomas-gk42  Copenhagen tells you all you need to know about quantum mechanics structurally. If you don't understand why, then you didn't study the topic carefully enough.
    1
  57.  @iyziejane  I got an award for excellence once. It's called a "physics PhD" title. Did you get one of those, too? ;-)
    1
  58. We have that. "Quanta are small amounts of energy.". Six words. "Observations are irreversible energy transfers.". Five words. "Quantum mechanics is a partition of unity that obeys relativity.". Ten words. Dude, your DK Is showing. Shove it back in. It's ugly. ;-)
    1
  59.  @dimitriospolymeros1497  Awh, Dude, now you are just feeling sorry for yourself, like every other kid who failed in high school and never recovered from the humiliation. High school neurosis trolls are a dime a dozen. You guys are boring like hell. :-)
    1
  60. You should bet your house on that. What could go wrong? :-)
    1
  61.  @STONECOLDET944  You should bet your house on Christ, too. That you won't tells me absolutely everything I need to know about you. ;-)
    1
  62.  @STONECOLDET944  Why are you feeling so sorry for yourself, right now? I wasn't the one who started it by posting bullshit. ;-)
    1
  63. Yes, you are missing a class on special relativity. There are no such thing as "before" and "after" in a relativistic universe.
    1
  64.  @physikus1123  Dude, most events are spacelike separated. That you feel uncomfortable with that doesn't mean you can exclude them. If you do you are missing the actual physical reason behind quantum mechanics. You need to develop a working intuition for relativity. ;-)
    1
  65.  @physikus1123  You were asking what you are missing. The answer is that you are missing a special relativity class. The reason behind the tensor product structure of quantum mechanics is special relativity. It allows for non-separable states that are nonetheless local (otherwise they would massively violate relativity and we would all have ansibles in our phones... except that we wouldn't even be here because the universe would have spontaneously self-combusted if energy could spread infinitely fast). :-)
    1
  66.  @physikus1123  Sabine has no clue about physics. Why is that even a question? ;-)
    1
  67.  @physikus1123  Yes, that's another 1+ million people who have no clue about physics. I am not a subscriber. I am, however, a physics PhD. Just how stupid do you want to appear here? ;-)
    1
  68. Statistical independence is testable.
    1
  69.  @Thomas-gk42  Let me give you some more attention. ;-)
    1
  70. Then somebody gives away that they didn't listen carefully when special relativity was explained to them. "At the same time" does not exist unless both events are happening at the same location. The timing of spatially separated events depends on the observer. For events with spacelike separation both event orders ("A before B" and "B before A") can be observed by different observers.
    1
  71. It's trivial. The only quanta you can measure are the quanta that the measurement system can absorb. If your measurement system consists of a spectrometer that can only absorb wavelengths between 500-1000nm, then it's impossible to get a measurement result of 1500nm. ;-)
    1
  72. You need to become more discerning in the kinds of people you listen to. ;-)
    1
  73. Absolutely nothing. She just likes to peddle that nonsense. :-)
    1
  74. Take a cake. Cut it into two randomly sized pieces. Put them together. What do you have? An whole cake. Cut two different randomly sized pieces. What do you have? The same whole cake. Do it again and again and again. Will you ever get anything other than the whole cake? That is what entanglement is. A kindergartener can understand that, don't you think? :-)
    1
  75. None of this has anything to do with statistics.
    1
  76.  @jonaswox  Yes, that is bullshit. If you roll dice and the outcome is "1", that's not statistics and it's certainly not probability. It's a cold, hard fact. If you roll dice ten times and the outcomes are two "1s" etc., then you have a statistical measure for that statistical sample outcome. To get from there to probability you have to take a giant leap of abstraction and assume that you can repeat the same experiment an infinite number of times AND that all repetitions are completely independent of each other. At that point you have left the realistic level because no experiment can be repeated independently an infinite number of times. And now you have a serious problem, because if you actually try to fit probability theory to physics naively then you will notice that it does not (and can not) obey any of the conservation laws and with that it's dead in the water as a microscopic theory. The correct microscopic theory still retains the same assumptions about experimental repeatability and independence but it is NOT probability theory but something completely different called "quantum mechanics", or, to put it more precisely, it's the unitary representation theory of the Poincare group.
    1
  77.  @jonaswox  I am a retired physics PhD, kiddo. I have never used any philosophy in my entire life. I simply stuck to facts. ;-)
    1
  78. The two types of physical interactions are called "reversible" and "irreversible". Measurement outcomes are, by definition, the results of irreversible processes. They can not be undone. Before such an irreversible process takes place there simply is no outcome. The idea that a quantum mechanical system has a state before it is being measured is simply 100% false. The same is true for "random" systems like dice in a classical setting, by the way. We are not teaching any of this very well in school, and most people simply don't spend enough thought on it to figure it out on their own.
    1
  79. I would ignore it because it is total bullshit. ;-)
    1
  80.  @billgardiner4858  Well, that explains why you are spewing so much of it. ;-)
    1
  81. Because of relativity. If the two measurement events have a space-like separation, then there is no causal connection. We can always find two observers (traveling at different relative velocities) who will claim a different event order. One will say A came before B, the other will say B came before A. Since the outcomes are independent of those claims they can't depend on the order. In other words, we have to decide if we want to keep quantum mechanics local or give up on special relativity. If we keep special relativity, then quantum mechanics can not be non-local. There is a workaround against this argument, but that's super-determinism, i.e. nature can do whatever it wants but it always hides the violations from physicists. That's the "lying universe" interpretation. I find that both useless and questionable. The only other possibility would be to find an experimental violation of special relativity. So far that has not been seen.
    1
  82. Schroedinger was simply confused, as were most of the other founders. You can find early papers by Heisenberg in which he gets things completely right but later he "self-corrects" and falls back on wrong semi-classical explanations. Erring is human. Erring about non-intuitive effects (whether they are trivial if understood correctly or not) doubly so.
    1
  83. There is nothing strange about the explanations. It's all just a geometric partition of unity that happens to obey relativity in addition. ;-)
    1
  84. The total angular momentum of the two quanta is zero, which means that they have opposite spin, IF we measure them with measurement devices that are perfectly aligned. If they are not aligned, then the outcomes are NOT opposite.
    1
  85. Hidden variables were never a thing. The only thing that was a thing and still is are people who aren't paying attention in science class. In this particular case it is your failure to pay attention in your class on special relativity that gets the best of you. ;-)
    1
  86. The wave function never changes. You simply don't know what a wave function is. ;-)
    1
  87. We never "lost locality". She is just bullshitting you. That's also the corner where the superdeterminism bullshit comes from. ;-)
    1
  88. How much have you been drinking? ;-)
    1
  89. You just gave us a good reason why one shall not use ChatGPT to get answers to physics questions. ;-)
    1
  90.  @mellkiades  In science you shouldn't believe anything. You should have been paying attention in science class so YOU could understand it. You didn't. Water under the bridge. ;-)
    1
  91.  @AA-wb6qz  All AIs are repeating the nonsense they learned on the internet from people like you who don't understand. They just put you back into the echo chamber of your own failed education on this topic. ;-)
    1
  92. Quantum mechanics describes all known matter and radiation phenomena at the microscopic level correctly. If you don't know that, then you simply didn't study enough physics, yet. Study longer and harder. ;-)
    1
  93. They did? Somebody should tell them. ;-)
    1
  94. We give you the correct language for quantum mechanics in high school: "A quantum is a small amount of energy.". If you can remember that, then you can easily learn how it works and why it works the way it does.
    1
  95. Have you been drinking again? ;-)
    1
  96.  @mvoetmann1  Dude, every introductory textbook on quantum mechanics will tell you that velocity is not a well defined property in quantum mechanics. Momentum is... for free fields. So, less drinking, more textbook studying. ;-)
    1
  97. One does not need the SE to do quantum physics. Heisenberg's matrices work perfectly find and they are much easier to understand than the SE. The real crime is that we are basically teaching von Neumann's synthesis without explaining where it came from. The math is all correct but the student can not connect it to physics. That's not a conceptual problem, it's just shoddy teaching.
    1
  98. They stand for A and B. I agree. It's trite. :-)
    1
  99. That is why physicists don't think in terms of "information" to begin with. It has no meaning in these contexts.
    1
  100. Science is the rational description and explanation of natural observations. What you are talking about is more like creative writing.
    1
  101.  @crawkn  Math doesn't work to predict the next event in your photon, electron etc. counter. NEXT! :-)
    1
  102.  @crawkn  A probability is an abstract. It's not a reality and one can not make it one because that would require an infinite number of repetitions of the same experiment. You are actually making the very mistake that you are accusing scientists of. You don't know the difference between the model and reality. :-)
    1
  103.  @crawkn  You are arguing that scientists don't know what they are doing. I am a scientist, kid, and I always knew exactly what I was doing in the high energy physics lab. Oh, wait... you have never seen one of those from the inside. ;-)
    1
  104.  @crawkn  Well, you have clearly also never taught proper science to your students. You have never even taught proper manners. To accuse an entire subpopulation of humans (we are about one million physicists on the planet) of a trivial intellectual error based on some nonsense you saw on the internet is the opposite of manners. ;-)
    1
  105. The good news is that quantum mechanics is not non-local. It's simply not separable, but that's an entirely different property. Most people just can't tell the difference.
    1
  106. Entanglement is simply the action of local conservation laws on multi-quantum states. Every theoretician knows "how" it works. Most of them just can't explain it well because they lack the intuition for the physics of it. It's a great example for a case where the "how" does not explain the "what". :-)
    1
  107. There is nothing to follow there. There is no such thing as "measurement independence". The results in quantum mechanics are highly dependent on the measurement. One can, at most, formulate it relativistically by saying that initial and final states in QFT can not be correlated by the two endpoints because from the viewpoint of any one local observer the two events are spacelike separated. :-)
    1
  108. It is an experimental fact that measurements in quantum mechanics depend on the measurement device. There is no here, here.
    1
  109. Because people do not like to think about reality as much as they like to think about oversimplifications of reality. Theorists who think about the world as Hamiltonian are still driving cars that require half a gallon of motor oil, even though in a Hamiltonian world there is absolutely no need for it since there is no friction. ;-)
    1
  110. All of physics is local. Quantum mechanics is not locally realist, but that's OK because the term "local realism" is philosophical bullshit. It has absolutely no scientific use and was never a topic in physics proper. ;-)
    1
  111. We always do. Sabine just doesn't know that because she is not an experimentalist. ;-)
    1
  112. The major problem with Bell's theorem is that it's not necessary. We know exactly what happens. There was never a need to come up with a formula for all the things that don't happen and that can't happen because of relativity.
    1
  113. When was the last time you have seen a particle?
    1
  114.  @prashanthramg9005  Unlike you I am a physics PhD who has performed trillions of quantum measurements. Let me give you a hint, kid: I have never seen a particle. And I know that neither have you. They don't exist. ;-)
    1
  115.  @prashanthramg9005  Photons and electrons are not particles. They are quanta of energy. That's a completely trivial but extremely important statement. Energy does not have a position and it does not have a path. It didn't have those properties in classical mechanics, either. Energy is a system property. When we talk about "a photon" what we mean is that flow of energy between two systems. "A photon" is the energy that a light source emits into the electromagnetic field or that an absorber/detector removes from the field. The emission and absorption energy do not need to be the same. A simple example of that is the Doppler effect. The electromagnetic field does not "know" the relative velocity between the emitter and the absorber. In the same way it also doesn't know the distance and the relative angle of polarizers (or magnetic fields for spin projection measurements on e.g. electrons). These facts are set by relativity (we can deduce the necessary form of the equations of quantum field theory directly from first principles). Bell didn't discover anything that wasn't known to a much higher degree, already. We have "the right theory". There is no need to classify all the wrong ones (a wrong theory is not even a theory by definition of "theory", so it's not even clear to me what the heck Bell was trying to do there).
    1
  116. Energy. :-)
    1
  117. Yes, you are wrong because neither quantum has a spin projection before the measurement takes place.
    1
  118. We are not measuring spin. We are measuring spin projections. The spin stays the same, but the spin projection distributions change depending on the angle of the measurement system's projection axis.
    1
  119. The universe is not non-local. Most people just don't understand what these words mean.
    1
  120. God and hidden variables are, indeed, very similar: they are both made up fairytales.
    1
  121.  @Thomas-gk42  There is no such thing as a "measurement problem". I have made trillions of quantum measurements myself and not once did I have a problem. You don't have to believe all the nonsense that uneducated people make up to fill their empty lives with. We did, by the way, tell you in high school what a measurement is: it's an irreversible energy transfer. We didn't use the word "irreversible" because that's more undergrad level physics, and we didn't tell you that the definition of a "photon" as a "quantum of energy" can be generalized, but that's all extremely trivial stuff. It's basically just preliminary definitions to get you started with real physics. There are no problems and questions here. There are only people who don't even know the basic definitions.
    1
  122.  @Thomas-gk42  Yes, all of that nonsense comes from people who have never made a single measurement in their entire lives. The folks who have (like me) know that measurement has NEVER been a problem. ;-)
    1
  123. We teach in high school that photons are small amounts of energy, but then students start binge drinking and they forget all about their primary education. ;-)
    1
  124. There is no such thing as spin without a spin measurement. That's no different from a pair of aces in poker. You don't have one until the dealer deals one to you.
    1
  125. Yes, but there are recent papers that show that one can temper even with entanglement based communication systems. They are not 100% secure.
    1
  126.  @TheDragonStratagem  I am simply giving you attention. That's what you are really here for. ;-)
    1
  127. Measurements are either independent and then the usual formulas of quantum mechanics apply or they are not independent and then these formulas do not apply. One can find plenty of case of both kinds in nature. We simply do not discuss the math required to deal with the non-independent cases much because it leads to a lot of ugliness that the independent case manages to avoid.
    1
  128. @ Independence means that one can not predict the next quantum using the previous n quanta. Radioactive sources are considered independent. The light of a laser OTHO is highly correlated and so consecutive measurements are not independent unless we wait for a long enough time between measurements. For independent measurements we can replace the physics of the actual physical source (ONE physical source!) with an (abstract!) ensemble of that source (the ensemble contains an infinite number of exact copies of the actual physical source). Quantum mechanics is an ensemble theory. One of its assumptions is that we can make that implicit replacement and so we do not have to think at all about the physics of the source. We also don't have to think about the physics of the detector any longer because unlike real detectors that have e.g. deadtimes, the ideal detector is exactly the same every time. Needless to say, only theorists have this luxury. Experimentalists are thinking about statistical dependence in sources and bunching, saturation, after pulses and other memory effects in detectors all the time. We don't have the luxury of the idealizations that the theorists are working with. ;-) So, yeah, anybody who thinks that physicists are not 100% aware of the problem is full of crap because they have never worked in an actual physics lab. ;-)
    1
  129. You wouldn't have learned much except that everybody was utterly confused.
    1
  130. No, there isn't. "A photon" is a small amount of energy that the "detector" system absorbs from the free electromagnetic field. Once that energy has been removed from the field it's gone. No other detector can measure it, again. Photons are therefor, by definition, nature's "singletons".
    1
  131. The problem is that this breaks unitarity and the probabilities won't add up to 100%.
    1
  132. It's neither. It's a just another consequence of relativity. The correlation between the two quanta in an entangled pair is a relativistic scalar, but the event order is observer dependent (Andromeda effect), hence the correlation can not have any cause and effect attached to it.
    1
  133. Yes, that's not how it works. ;-)
    1
  134. @ It's not spin that we are measuring. We are measuring spin projections that have a measurement system dependent projection axis.
    1
  135. @ Nobody can give you an example of non-locality because the universe is perfectly local. It's in basically every introductory chapter of every relativistic quantum field theory book.
    1
  136. @ There is nothing intriguing about quantum mechanics. You can derive it from first principles in a few dozen pages of slightly above high school level math. Most people simply don't know how. The people who are telling you all these outrageous stories about it are all suffering from Dunning-Kruger.
    1