Thursday, June 11, 2020

Quantum Superpositions Are Relative

At 4AM I had an incredible insight.

Here’s the background.  I’ve been struggling recently with the notion of gravitational decoherence of the quantum wave function, as discussed in this post.  The idea is neither new nor complicated: if the gravitational field of a mass located in Position A would have a measurably different effect on the universe (even on a single particle) than the mass located in Position B, then its state cannot be a superposition over those two locations.

Generally, we think of impacts between objects/particles as causing the decoherence of a superposition.  For instance, in the typical double-slit interference experiment, a particle’s wave state “collapses” either when the particle impacts a detector in the far field or we measure the particle in one of the slits by bouncing a photon off it.  In either case, one or more objects (such as photons), already correlated to the environment, get correlated to the particle, thus decohering its superposition.

But what if the decohering “impact” is due to the interaction of a field on another particle far away?  Given that field propagation does not exceed the speed of light, when does decoherence actually occur?  That’s of course the question of gravitational decoherence.  Let’s say that mass A is in a superposition over L and R locations (separated by a macroscopic distance), which therefore creates a superposition of gravitational fields fL and fR that acts on a distant mass B (where masses A and B are separated by distance d).  For the sake of argument, mass B is also the closest object to mass A.  Let’s say that mass B interacts with the field at time t1 and it correlates to fL.  We can obviously conclude that the state of mass A has decohered and it is now located at L... but when did that happen?  It is typically assumed in quantum mechanics that “collapse” events are instantaneous, but of course this creates a clear conflict between QM and special relativity.  (The Mari et al. paper in fact derives its minimum testing time based on the assumption of instantaneous decoherence.)

This assumption makes no sense to me.  If mass B correlates to field fL created by mass A, but the gravitational field produced by mass A travels at light speed (c), then mass A must have already been located at L before mass B correlated to field fL – specifically, mass A must have been located at L on or before time (t1 - d/c).  Thus the interaction of mass B with the gravitational field of mass A could not have caused the collapse of the wave function of mass A (unless we are OK with backward causation).

So for awhile I tossed around the idea that whenever a potential location superposition of mass A reaches the point at which different locations would be potentially detectable (such as by attracting another mass), then it would produce something (gravitons?) that would decohere the superposition.  In fact, that’s more or less the approach that Penrose takes by suggesting that decoherence happens when the difference in the gravitational self-energy between spacetime geometries in a quantum superposition exceeds what he calls the “one graviton” level.

The problem with this approach is that decoherence doesn’t happen when differences could be detected... it happens when the differences are detected and correlated to the rest of the universe.  So, in the above example, what actual interaction might cause the state of mass A to decohere if we are ruling out the production (or even scattering) of gravitons and neglecting the effect of any other object except mass B?  Then it hit me: the interaction with the gravitational field of mass B, of course!  Just as mass A is in a location superposition relative to mass B, which experiences the gravitational field produced by A, mass B is in a location superposition relative to mass A, which experiences the gravitational field produced by B.  Further, just as from the perspective of mass B at time t1, the wave state of mass A seems to have collapsed at time (t1 - d/c)... also from the perspective of mass A at time t1, the wave state of mass B seems to have collapsed at time (t1 - d/c).

In other words, the “superposition” of mass A only existed relative to mass B (and perhaps the rest of the universe, if mass B was so correlated), but from the perspective of mass A, mass B was in a superposition.  What made them appear to be in location superpositions relative to each other was that they were not adequately correlated, but eventually their gravitational fields correlated them.  When mass B claims that the wave state of mass A has “collapsed,” mass A could have made the same claim about mass B.  Nothing actually changed about mass A; instead, the interaction between mass A and mass B correlated them and produced new correlation information in the universe.

Having said all this, I have not yet taken quantum field theory, and it’s completely possible that I’ve simply jumped the gun on stuff I’ll learn at NYU anyway.  Also, as it turns out, my revelation is strongly related, and possibly identical, to Carlo Rovelli’s Relational interpretation of QM.  This wouldn’t upset me at all.  Rovelli is brilliant, and if I’ve learned and reflected enough on QM to independently derive something produced by his genius, then I’d be ecstatic.  Further, my goal in this whole process is to learn the truth about the universe, whether or not someone else learned it first.  That said, I think one thing missing from Rovelli’s interpretation is the notion of universal entanglement that gives rise to a preferred observer status.  If the entire universe is well correlated with the exception of a few pesky microscopic superpositions, can’t we just accept that there really is just one universe and corresponding set of facts?  Another problem is the interpretation’s dismissal of gravitational decoherence.  In fact, it was my consideration of distant gravitational effects on quantum decoherence, as well as implications of special relativity, that led me to this insight, so it seems odd that Rovelli seems to dismiss such effects.  Another problem is the interpretation’s acceptance of Schrodinger’s Cat (and Wigner’s Friend) states.  I think it extraordinarily likely -- and am on a quest to discover and prove -- that macroscopic superpositions large enough to encompass a conscious observer, even a cat, are physically impossible.  Nevertheless, I still don’t know much about his interpretation so it’s time to do some more reading!

Sunday, June 7, 2020

How Science Brought Me To God

This post was inspired by my sister, who has been struggling recently with questions about God, purpose, meaning, and many other big philosophical questions.

Let me start by saying that I’m not a Christian (or a Buddhist or a Muslim or a Jew or a Rastafarian blah blah blah), and never will be.  Christianity is a set of very specific stories and beliefs, of which the belief in a Creator is a tiny subset.  Belief in God does not imply belief in Christianity or any other religion.  It is truly astonishing how many scientists (and physicists in particular) don’t seem to understand that last sentence.  It’s incredible how often physicists will say something like: “When I was in Sunday School, I learned about Jesus walking on water.  But as a scientist, I learned that walking on water violates the laws of physics.  Therefore god does not exist.”  The conclusion simply doesn’t follow from the premises.

In my own progress in physics, I am finding much of the academic literature infested with bad logic and unsound arguments.  One of my more recent posts points to a heavily cited article that claimed to empirically refute the consciousness-causes-consciousness hypothesis (“CCCH”).  The authors started by characterizing CCCH as an if-then statement in the form of AàB (read “A implies B” or “if A, then B”), which was essentially correct.  (The actual statements are irrelevant to the point I’m making in this post, but my actual paper can be found here.)  Then, without explanation, they re-characterized CCCH as AàC, but this would only be true if BàC.  Setting aside the fact that BàC blatantly contradicts quantum mechanics, the authors didn’t even seem to notice the unfounded logical jump they had made.  Simply having taken graduate-level philosophical logic has already provided me a surprising leg-up in the study and analysis of physics.

Why do I take such pains to explain that my belief in God does not imply belief in any particular religion or set of stories?  Because my search for a physical explanation of consciousness, and my pursuit of some of the hard foundational questions in physics, already puts me on potentially thin ice in the physics academy, and mentioning God (with a capital G) may very well put me over the edge into the realm of “crackpot.”  Luckily, I’m in the position of not needing to seek anyone’s approval; having said that, I would ultimately like to collaborate with and influence other like-minded physicists and don’t want to immediately turn them off with any suggestion that I’m a Christian.  I also don’t intend to turn off any Christian readers... my wife and one of my best friends are Christians.  My point is that Christianity includes a very specific set of concepts and stories that far exceed mere theism and may be understandably off-putting to physicists.

With all the caveats in place, here’s the meat of this blog post: Science has in fact brought me to God, in large part via the Goldilocks Enigma, better known as the “fine-tuning” problem in physics.

Paul Davies, a cosmologist at Arizona State, wrote a fascinating book called The Goldilocks Enigma.  Essentially, there are more than a dozen independent parameters, based in part on the Standard Model of particle physics, that had to be “fine-tuned” to within 1% or so in order to create a universe that could create life.  (The phrase “fine-tuned” itself suggests a Creator, but that’s not how Davies means it.)  One example might be the ratio of the gravitational force to the electromagnetic force.  A star produces energy via the fusion of positively charged nuclei, primarily hydrogen nuclei.  Electrostatic repulsion makes it difficult to bring two fusible nuclei sufficiently close, but gravity solves this problem if the object is really massive, like a star.  The core of a star then experiences the quasi-equilibrium condition of gravity squeezing lots of hydrogen nuclei together counterbalanced by the outward pressure of an extremely high-temperature gas, thus producing fusion energy at more-or-less constant rate.  This balance in our Sun gives it a lifetime of something like 10 billion years before its fuel will be mostly spent.

Here’s the problem: if the gravitational force had been 1% higher than it is, then the Sun would have burned up far too quickly for life to evolve, while if the force had been 1% less than it is, the Sun would have produced far too little radiation for life to evolve.  (It is generally thought that liquid water, which exists in the narrow range of 273-373K, is a requirement for life, although this is not necessary for the current argument.)  In other words, the ratio of gravity to electric repulsion had to be in the “Goldilocks” zone: not too big, not too small... just right.

The likelihood of that ratio being “just right” is very small.  And you might think this is just a coincidence.  That’s certainly what a lot of physicists will say.  But remember that there are at least 26 such free parameters in nature that happen to be “just right” in the same way, and (small probability)^26 = (really freaking unbelievably tiny probability).  The probability is so tiny as to be effectively zero.

If you have already dismissed any possibility of a Creator, then one way – perhaps the only way – to explain away such a fantastically tiny probability is to posit the existence of infinitely many universes and then invoke the so-called “Anthropic Principle” to conclude that such an unlikely event must be possible because, if it weren’t, we wouldn’t exist to notice!  After all, if everything that is possible actually exists somewhere, then extremely unlikely events, even events whose probability is actually zero, will occur.  In other words, (infinitesimal) * (infinity) = 1.  Said another way:  0 * ∞ = 1.

For the record, I made the same argument in a book I wrote at age 13, called Knight’s Null Algebra, which claimed to “disprove” algebra.  Just as anything logically follows from a contradiction (“If up is down, then my name is Bob” is a true statement), anything follows from infinity.  Infinity makes the impossible possible.  But this is philosophical nonsense.  Infinity doesn’t exist in nature.  Nevertheless, many physicists and cosmologists with (as far as I know) functioning cerebrums actually believe in the existence of infinitely many universes, although they give it a fancy name: the Multiverse.

Here are my problems with the Multiverse:
·         There is not a shred of empirical evidence that there is such a thing.
·         Because the Multiverse includes universes that are beyond our cosmological horizon and are forever inaccessible to us, no empirical evidence ever can exist to test the concept.
·         Any concept or hypothesis that cannot be tested is not in the realm of science.
·         Any scientist who endorses the Multiverse concept is not speaking scientifically or as a scientist (even though s/he may pretend to).

Setting aside all these problems with the Multiverse concept, it should be pointed out that anyone who dismisses any possibility of a Creator, and thus desperately embraces infinity to dismiss the Goldilocks enigma, is not being scientific anyway.  One can make arguments for or against the existence of God; one can lean toward theism or atheism; but anyone who states with certainty that God does or does not exist is not speaking scientifically.  And that’s OK.  There’s nothing wrong with a scientist having opinions one way or another or with making arguments one way or another, just as I’ve done in this post.  But it is a problem when scientists speak from the academic pulpit, intimidating people with their scientific degrees and credentials, to bully people into accepting their philosophical opinions as if they were scientific facts.  (Richard Dawkins should have lost his membership to the scientific academy long ago, now that he spews untestable pseudoscientific gibberish, but has in fact been celebrated instead of ostracized by the academy.)

My point is this: I believe that the Goldilocks Enigma is a very strong reason to believe in a Creator, while the Multiverse counterargument is an untestable and nonscientific theory usually uttered by people (scientists or otherwise) who are not speaking scientifically.

I am truly and utterly amazed and overwhelmed by the vastness, beauty, and unlikeliness of the Universe.  And the more I learn about physics, the more awed I become.  For instance, if the information in the universe is related to universal entanglement, then every object is entangled with essentially every other object in the universe in ways that correlate their positions and momenta to within quantum uncertainty.  That is absolutely, utterly, incomprehensively amazing.  The more I learn about physics, the closer I come to God.

Saturday, June 6, 2020

Unending Confusion in the Foundations of Physics

Quantum mechanics is difficult enough without physicists mucking it all up.  Setting aside the problem that they speak in a convoluted language that is often independent of what’s actually happening in the observable physical world, they are sometimes fundamentally wrong about their own physics.

In 2007, a researcher named Afshar published a paper on a fascinating experiment in which he was able to infer the existence of a double-slit interference pattern when thin wires placed where destructive interference would be expected failed to significantly reduce the amount of light passing through.  It was clever and certainly worthy of publication.

But he took it a step too far and stated that the experiment showed a violation of wave-particle complementarity – in other words, he asserted that the photons showed both wave-like behavior and particle-like behavior at the same time.  The first is correct: the existence of interference in the far field of the double-slit indicated the wave behavior.  But the second (the simultaneous particle-like behavior) is not correct, as it depended on his claim that which-way information, which inherently does not and cannot exist in a superposition over two slits, exists retroactively through a later measurement.

I feel like Afshar can be excused for this mistake, for two reasons.  First, the mistake has its origins in a very reputable earlier reference by famed physicist John Wheeler.  Second, his experiment was new, useful, and elucidating for the physics community.  Having said that, the mistake represents such a fundamental misunderstanding of the very basics of quantum mechanics that it should have been immediately and unambiguously refuted – and then brought up no more.  But that’s not what happened.  What happened is this:

·         The paper is cited by over a hundred papers, very few of which refute it.
·         Among those that refute it, several refute it incorrectly.
·         Those that refute it correctly use over a hundred pages and several dozen complicated quantum mechanics equations.  Their inability to address and solve the problem clearly and succinctly only obfuscates what is already an apparently muddled issue.

Here is my two-page refutation of Afshar.

How exactly are physics students ever going to understand quantum mechanics when the literature on the foundations of physics is so confused and internally inconsistent?

Tuesday, June 2, 2020

Consciousness, Quantum Mechanics, and Pseudoscience

The study of consciousness is not currently “fashionable” in the physics community, and the notion that there might be any relationship between consciousness and quantum mechanics and/or relativity truly infuriates some physicists.  For instance, the hypothesis that consciousness causes collapse (“CCC”) of the quantum mechanical wave function is now considered fringy by many; a physicist who seriously considers it (or even mentions it without a deprecatory scowl) risks professional expulsion and even branding as a quack.

In 2011, two researchers took an unprovoked stab at the CCC hypothesis in this paper.  There is a fascinating experiment called the “delayed choice quantum eraser,” in which information appears to be erased from the universe after a quantum interference experiment has been performed.  The details don’t matter.  The point is that the researchers interpret the quantum eraser experiment as providing an empirical falsification of the CCC hypothesis.  They don’t hide their disdain for the suggestion that QM and consciousness may have a relationship.

The problem is: their paper is pseudoscientific shit.  They first make a massive logical mistake that, despite the authors’ contempt for philosophy, would have been avoided had they taken a philosophy class in logic.  They follow up that mistake with an even bigger blunder in their understanding of the foundations of quantum mechanics.  Essentially, they assert that the failure of a wave function to collapse always results in a visible interference pattern, which is just patently false.  They clearly fail to falsify the CCC hypothesis.  (For the record, I think the CCC hypothesis is likely false, but I am reasonably certain that it has not yet been falsified.)

Sure, there’s lots of pseudoscience out there, so why am I picking on this particular paper?  Because it was published in Annalen der Physik, the same journal in which Einstein published his groundbreaking papers on special relativity and the photoelectric effect (among others), and because it’s been cited by more than two dozen publications so far (often to attack the CCC hypothesis), only one of which actually refutes it.

What’s even more irritating is that the paper’s glaring errors could easily have been caught by a competent journal referee who had read the paper skeptically.  If the paper’s conclusion had been in support of the CCC hypothesis, you can bet that it would have been meticulously and critically analyzed before publication, assuming it was considered for publication at all.  But when referees already agree with a paper’s conclusion, they may be less interested in the logical steps taken to arrive at that conclusion.  A paper that comes to the correct conclusion via incorrect reasoning is still incorrect.  A scientist that rejects correct reasoning because it results in an unfashionable or unpopular conclusion is not a scientist.

Here is a preprint of my rebuttal to their paper.  Since it is intended to be a scholarly article, I am much nicer there than I’ve been here.

Monday, May 25, 2020

Speaking the Wrong Language

In my last post, I pointed out a fundamental problem in a particular paper – although the same problem appears in lots of papers: specifically, that there is no way to test whether an object is in a quantum superposition.  I feel like this is a point that many physicists and philosophers of physics overlook, so to be sure, I went ahead and posted the question on a few online physics forums, such as this one.  Here’s basically the response I got:
Every state that is an eigenstate of a first observable is obviously in a superposition of eigenstates of some second observable that does not commute with the first.  Therefore: of course you can test whether an object is in a quantum superposition.  Also, you are an idiot.
OK, so they didn’t actually say that last part, but it was clearly implied.  If you don’t speak the language of quantum mechanics, let me rephrase.  Quantum mechanics tells us that there are certain features (“observables”) of a system that cannot be measured/known/observed at the same time, thus the order of measurement matters.  For example, position and momentum are two such observables, so measuring the position and then the momentum will inevitably give different results from measuring the momentum and then the position – that is, the position and momentum operators do not commute.  And because they don’t commute, an object in a particular position (that is, “in an eigenstate of the position operator”) does not have a particular momentum, which is to say that it is in a superposition of all possible momenta.  In other words, the above response basically boils down to this: quantum mechanically, every state is a superposition.

Fine.  The problem is that this response has nothing to do with the question I was asking.  I ended up having to edit my question to ask whether any single test could distinguish between a “pure” quantum superposition versus a mixed state (which is a probabilistic mixture), and even then the responses weren't all that useful.

This is why I think the big fundamental problems in physics will probably not be solved by insiders.  They speak a very limited language that, by its nature, limits a speaker’s ability to discover and understand the flaws in the system it describes.  My original question, I thought, was relatively clear: is it actually possible, as Mari et al. suggest, to receive information by measuring (in a single test) whether an object is in a macroscopic quantum superposition?  But when the knee-jerk response of several intelligent quantum physicists is to discuss the noncommutability of quantum observables and come to the irrelevant (and, frankly, condescending) point that all states are superpositions and therefore of course we can test whether an object is in superposition – well, it makes me wonder whether they actually understand, at a fundamental level, what a quantum superposition is.  I feel like there’s a huge disconnect between the language and mathematics of physics, and the actual observable world that physics tries to describe. 

Tuesday, May 19, 2020

It is Impossible to Measure a Quantum Superposition

In a previous post, I discussed how and to what extent gravity might prevent the existence of macroscopic quantum superpositions.  There has been surprisingly little discussion of this possibility and there is still debate on whether gravity is quantized and whether gravitational fields are, themselves, capable of existing in quantum superpositions.

Today I came across a paper, "Experiments testing macroscopic quantum superpositions must be slow," by Mari et al., which proposes and analyzes a thought experiment involving a first mass mA placed in a position superposition in Alice’s lab, the mass mA producing a gravitational field that potentially affects a test mass mB in Bob’s lab (separated from Alice’s lab by a distance R), depending on whether or not Bob turns on a detector.  The article concludes that special relativity puts lower limits on the amount of time necessary to determine whether an object is in a superposition of two macroscopically distinct locations.

The paper seems to have several important problems, none of which have been pointed out in papers that cite it, notably this paper.  For example, its calculation of the entanglement time TB assumes that correlation of the location of test mass mB with the gravitational field of mass mA occurs when the change in position δx of the test mass mB exceeds its quantum uncertainty Δx, which seems like a reasonable argument – except that they failed to include the increase in quantum uncertainty due to dispersion.  (This is particularly problematic where they let Δx be the Planck length!)  Another problem is their proposed experiment in Section IV: Alice is supposed to apply a spin-dependent force on the mass mA which results in different quantum states, depending on whether or not Bob turned on the detector, but both quantum states correlate to mass mA located at L (instead of R).  The problem is that by the time she has applied the force, Bob’s test mass mB has presumably already correlated to the gravitational field produced by Alice’s mass mA located at L or R, but how could that happen before Alice applied the force that caused the mass mA to be located at L?

But the biggest problem with the paper is not in their determination of the time necessary to determine whether an object is in a superposition of two macroscopically distinct locations.  No – the bigger problem is that, as far as I understand, there is no way to determine whether an object is in a superposition at all! 

Wait, what?  Obviously quantum superpositions exist.

Yes, but a superposition is determined by doing an interference experiment on a bunch of “identically prepared” objects (or particles or masses or whatever).  The idea is that if we see an interference pattern emerge (e.g., the existence of light and dark fringes), then we can infer that the individual objects were in coherent superpositions.  However, detection of a single object never produces a pattern, so we can’t infer whether or not it was in a superposition.  Further, the outcome of every interference experiment on a superposition state, if analyzed one detection at a time, will be consistent with that object not having been in superposition.  A single trial can confirm that an object was not in a superposition (such as if we detect a blip in a dark fringe area), but no single trial can confirm that the object was in a superposition.  Moreover, even if a pattern does slowly emerge after many trials, every pattern produced by a finite number of trials – and remember that infinity does not exist in the physical world – is always a possible random outcome of measuring objects that are not in a superposition.  We can never confirm the existence of a superposition, but lots and lots of trials can certainly increase our confidence.

In other words, if I’m right, then every measurement that Alice makes (in the Mari paper) will be consistent with Bob's having turned the detector on (and decohered the field) -- thus, no information is sent!  No violation of special relativity!  No problem!

Look, I could be wrong.  I’ve been studying the foundations of quantum mechanics independently for a couple of years now, and very, very few references point out that there’s no way to determine if any particular object is in a quantum superposition, which is also why it’s taken me so long to figure it out.  So either I’m wrong about this, or there’s some major industry-wide crazy-making going on in the physics community that leads to all kinds of wacky conclusions and paradoxes... no wonder quantum mechanics is so confusing!

Is there a way to test whether a particular object is in a coherent superposition?  If so, how?  If not, then why do so few discussions of quantum superpositions mention this?

Update to this post here