# So Now It’s 2022

That’s weird to me. I’m from the 1950s and can measure my life in scores of years (three-and-mumble). I was an avid science fiction reader by the 1960s, so recall an era where we wondered if the year 1984, let alone 2001, would be anything like the famous book.

As it turned out, in both cases: No. Respectively fortunate and unfortunate. The future turned out less extreme (but no less “interesting”). Both demonstrate the difficulty of prediction, a problem science fiction illustrates more often than not.

That said, the other face of Janus looks forward…

The look back in the previous post ran longer than I expected, so there was no room for a look forward. Same thing happened last year: one post to look back; one to look forward. Two faces, two posts, seems apt.

Speaking of running longer, that’s a bridge between the backward and forward views. My average word count per post has certainly increased over the years:

A significant jump after a year off, and something of an upward trend since. The posts per year numbers echo the words per post data with notable exceptions in 2018 and 2021:

Just wasn’t cranking them out last year, but I was more verbose than ever.

That does reflect a conscious loosening of the count leash. I used to see 1200–1500 as a negotiable ceiling, but lately I’ve been feeling very comfortable up to 1700. The lid floats around 1800–2000. Some run longer. Very rarely I’ll break 2500.

I may try for more brevity by not combining multiple TV or movies reviews into a single post. That makes sense if I don’t have much to say about any of them and they’re related by some theme (even as broad as “anime”), but I’ve had too many of those end up with high word counts. Doing shorter single posts would doubly reduce the average by increasing the number of posts while reducing the number of words in those posts.

That said, a lot of the other posts I’m thinking about are technical enough to end up with lots of words in them. Such posts account, in part, for the upward trend.

I’m not gonna give it a lot of thought. It is what it is.

§ §

Jumping into increasingly distant space, I read that, on Saturday the James Webb Space Telescope (JWST) successfully deployed its sunshield. If you’re aware of the incredible effort it took to get to this point, this is awesome news. A gem to start the new year.

A full-scale model of the JWST at Goddard Space Flight Center and the team that worked on it there (mid-September 2005). [photo NASA]

The telescope is optimized for seeing in the near- and mid-infrared, which allows it to search for highly red-shifted ancient galaxies. That’s exciting because observing large ancient galaxies might tip the dark matter question in favor of MOND theories.

Infrared is radiant heat, so telescopes must be as cold as possible. Otherwise the heat of the telescope obscures the image like a light leak in a camera. The JWST will orbit in Earth’s L2 Lagrange point — one-and-a-half million kilometers away from Earth on the opposite side from the Sun. (In comparison, the Moon orbits a bit over one-third of a million km away.)

The point is, the telescope is roughly as far from the Sun as the Earth is — hardly the chill of the outer Solar system, let alone deep space. That means the ‘scope needs a sunshield. A very large and effective sunshield. More to the point, a sunshield much too large to fit in a rocket.

As I mentioned above, 2001 was wrong, we’re still not to the point of serious construction in space, so the large sunshield had to be a 344-step origami trick performed after launch.

Blueprint of the JWST [image NASA]

Twenty-five years of development and the efforts of tens of thousands of people and billions of tax-payer dollars down to 344 sequential steps, any one of which, should it fail, dooms the ‘scope.

And it went perfectly. Must have been one hell of a New Year’s party.

A huge thank you and congratulations to all involved!

§ §

Crossing space from science to science fiction, last year I finally got around to reading Octavia Butler. Long overdue and regrets for not doing it sooner. She more than deserves the acclaim I too long ignored.

This year, already, I finally got around to another author who has been on my radar for a while. Not for as long as with Butler, nor with the same degree of acclaim, but with a strong sense he might be my sort of hard SF author. I’m speaking of Alastair Reynolds.

Born in the mid-1960s, he’s a contemporary writer — one with a Ph.D. in astrophysics and former career as a research astronomer for the ESA. Attractive credentials for a hard SF author. That kind of background is what attracts me to authors such as Greg Egan, Robert L. Forward, Rudy Rucker, and, of course, Isaac Asimov.

As with Butler, I’m sure I’ve encountered his short stories in various collections, but few and far between enough that any sense of his was lost in the general clamor of short story authors. Now I’ve read two of his novels, and I liked them a lot. Definitely my sort of hard SF author.

Reynolds writes (at least in these) of the far future. In one case, the standalone novel House of Suns (2008), many millions of years from now. I also read the first book of his Revelation Space series, Revelation Space (2000), which is set in the 2500s — merely five-hundred years from now.

And while he is not without his indistinguishable-from-magic technology, both books take place in Einstein’s universe — no FTL, no magic warp drive. I have a major soft spot for science fiction that respects the speed of light.

Warp drive is a necessary gimme to tell the kind of story that makes the galaxy (or universe) more an analogue for Earth. But the same bent I have towards hard SF also inclines me towards an appreciation for a galaxy-sized story told in the framework of special relativity.

[Which I remind you says: (1) causality; (2) special relativity; (3) FTL. Pick two.]

So, I’m liking Reynolds a lot and looking forward to reading more. I’m currently waiting for my turn with the next book in the Revelation Space series. Free library books are great, but sometimes you wait.

§ §

Switching back to science, but from the vast to the tiny, at some point last year I got a little overloaded by how much more there is to learn about the mathematics of quantum mechanics. Looking back, I’ve learned a lot, but I’m still in the foothills in some regards. I needed a break from looking up at the mountain.

It’s not that the math is actually that hard, at least in the basics. There are things incredibly tedious to calculate (fortunately, computers are fast, accurate, and don’t get bored), and some things are intractable to normal computation (quantum computers will help). The math used, however, isn’t that tough. It’s mostly just calculus. My problem is that my calculus skills (such as they even are) fade out between derivatives and integrals.

The actual hard part is breaking away from physical intuition about how reality works and wrapping one’s head around what the mathematics says.

[A major puzzle in QM involves the ontology behind the math. Because it’s an abstraction and description of reality, all math is epistemic. But as a parabola abstracts and describes the arc of a physical baseball’s motion, the quantum mechanics math must be derived from something physical and real. If only we knew what it was.]

In any event, after a breather and letting things settle into shape, I’m ready to start climbing again. If I watch that MIT YouTube course again, my guess is I’ll get a lot more out of it.

§ §

I’ve long heard the complaint about older men wearing old clothes and resisting the efforts of family and friends to “throw that old shit away!” And rightfully so; holes and threadbare aren’t a great look no matter how comfortable and memory rich. My dad was certainly guilty — that old red flannel shirt — and guess who has his own red flannel shirt he really ought to just toss.

Hence the new forward looking rule about, after wearing the clean socks, underwear, tee-shirts, or sweaters, one last time, seriously consider, and lean strongly towards, just throwing that shit away. It’s not like I don’t have plenty and aren’t an Amazon Prime order away from more.

The purge has begun!

Now,… speaking of word count (which is under 1500), nuf sed.

Stay telescopic, my friends! Go forth and spread beauty and light.

The canonical fool on the hill watching the sunset and the rotation of the planet and thinking what he imagines are large thoughts. View all posts by Wyrd Smythe

#### 31 responses to “So Now It’s 2022”

• Wyrd Smythe

There is a link in the post, but here’s the unfolding video:

• Wyrd Smythe

Speaking of quantum mechanics, Anil Ananthaswamy has an article in the January Scientific American about a possible test for Bohmian mechanics. Briefly, at extremely short distances, the prediction curves for particle time of flight (a curve that varies due to Uncertainty) differ between Bohmian and Copenhagen formulations of QM. At longer (thus far testable) distances, the two are indistinguishable.

It has, in part, to do with the separation of time from other observable quantum properties. There is no time operator the same way there is a position (or momentum or spin) operator. One version of the Schrödinger equation is even time-independent. The version that evolves over time assumes a t=0 state and a current t as input.

But even in Relativity time is distinct from space. Its signature is different in the spacetime interval, either (+,+,+,-) or (-,-,-,+), depending on whether one prefers positive or negative space-like intervals (respectively).

• Brian

I’m often amazed at how much larger space probes or rovers are than I envisage them to be (when most images are of them in space or within a landscape with no point of reference); that image of the full-scale model of JWST with the crowd of people provides such a perspective – I’m staggered; it’s twice as large as I thought it was!

The amount of money that gets spent on such things is also vast and barely comprehendible; I recently read David Whitehouses’ account of such things in his book Space 2069.

• Wyrd Smythe

I spent quite a bit of time pondering which images of the JWST to use. I really loved the blueprint, because I love blueprints and maps (and if you click through to the source and look at a big image, the text is in Latin). But of all the assembly pictures and artist renderings, that full-sized model with all those people is the one I kept coming back to. For exactly that reason. “Holy shit! That thing is huge!!”

Yeah, the money is beyond imagining to us. The flow through governments and huge corporations; those numbers just don’t have meaning to someone who cares about a paycheck (or pension). The planning and the need to get so many people on one page for so long is mind-blowing, too.

The length of time this stuff takes, I believe, is a huge impediment for our space exploration chances. It takes so much time to explore space, even with robots that can take high G. We need very long-term commitment, decades, if not hundreds of years. Fully exploring the galaxy would take millions. But democracy pulls the pendulum in both directions, sometimes to extremes, so committing to four more years is a challenge. Committing to a hundred-year project? Hard to imagine us pulling that off.

• SelfAwarePatterns

On word counts, I’ve discovered that somewhere around 750 words appears to be my natural spot when I post on one particular topic. Getting shorter seems to take a lot of work, although when I try I can usually get it down to 600 or so. Of course, if I let the post sit in drafts, more points always occur to me and it tends to grow.

I’ve actually been thinking the same thing about entertainment posts. I’ve experimented lately with putting multiple things together, and it helps when I only have a few tidbits about each show. On the other hand, those could be short posts and they’d be easier to find and link to.

Good point about needing warp drive to make the galaxy more like the contemporary world. Interestingly, there are other ways to do it, like what Cowboy Bebop and the Gundam franchise do; just have a bunch of space colonies allowing the same range of polities and cultures. But I can also see why a lot of writers these days just opt for a fantasy world, like a steampunk one. It allows for the same commentary about modern day but with a similar distance to get around people’s partisan reflexes.

Have to admit I’m pretty bad about wearing clothes until they’re ready to give up the ghost. New clothes are just so uncomfortable. It seems like I have to go through multiple instances before finding one that will be a keeper.

That Scientific American article sounds interesting. Hope they put it on their site. (Although I rarely check them anymore. Too much paywalling and low quality content.)

• Wyrd Smythe

Now you’ve gotten me thinking about looking at my word count numbers more closely. In the WP data, the finest granularity I have is posts and words per month. I do load the XML export file into an SQLite database, so I do have a way to scan individual posts… Hmmm… I have code that scans words in posts already. It creates a vocabulary index. It should be easy to adapt to giving me individual post word counts. Might end up being today’s little project… 🙂

You’re right about individual posts being easier to find. That runs through my mind in those collective posts. In some cases, the first one is the one I care about most, but I do worry about the ones getting second billing. I think I’ll try to stick to single reviews of shows I either really liked or disliked. Shows that give me a strong reason to write about them. The blog is meant to have an autobiographical aspect, but I think I’ll try to be more selective.

The size of space is a real challenge! Cowboy Bebop has inter-system gates, and The Expanse has quasi-magical (“very effective”) drives. The JWST needs 30 days to reach the L2 point. (“And that’s just peanuts compared to space.”) Even the transporters on Star Trek shrunk space down to manageable size. Come to think of it, we do the same thing on Earth sometimes: edit out travel time by horse, car, foot, etc. I suppose it ties into the dream-like thing where distance doesn’t matter.

I’ve bought a lot of clothes at places like Target, and I’ve learned that when I find something I like, be it tee-shirts or whatever, it’s best to buy a number of them at once. Target, especially, changes styles regularly, and items I’ve liked have vanished forever. Buying a bunch means they don’t wear out as quickly either and you can have different color options.

I am so not a fan of SciAm. I used to be. It used to be my favorite magazine. I subscribed to the hard copy starting in the late 1960s and kept that subscription until the 2000s when I finally let it lapse. They’ve gotten worse since for exactly the reasons you mention. I’m paying \$9.99/mo for Apple News, which gives me an ad-free newsfeed and access to a lot of e-magazines, SciAm among them. So far it’s been worth the ten bucks a month.

Be pretty weird of Bohmian mechanics turned out right!

Which reminds me, I was thinking about The Absence in House of Suns. I don’t know if it’s what Reynolds had in mind for it, but it occurs to me it could be the result of the wormhole needing to prevent any shift in relative simultaneity. As you know, even low-velocity motion here results in a large shift of our “now” in Andromeda. If a wormhole connects our “now” with some “now” there, which moment in time is that there? It potentially could be any moment there not in our current light cone (because that’s the range in which simultaneity is relative and can be shifted). That’s a range of +/- 2.5 million years.

Now I don’t see why blocking light would matter, the light comes from within our light cone, but locking the wormhole to a specific “now” there might have a side effect of making Andromeda hidden from here. Maybe The Absence is more of a consequence than an intended effect?

• SelfAwarePatterns

I’m with you on thinking you’ll do certain things on the blog. I used to make predictions about what I would write about and how I’d do it, but I stopped doing those years ago. My miss rate was just too high.

Your points about “peanuts compared to space” reminds me of a blog post Linda Nagata did a while back, contrasting her stories with typical space opera. She noted how space opera usually trivializes the vastness of space with warp drive, hyperspace, etc, while she prefers to celebrate it. Reynolds, when recommending her book, Vast, cited her as an influence. (Although the earliest short stories in his Revelation Space universe predate her books, so the influence must have been subtle.)

Yeah, I’ve done the, “This is comfortable. Let me buy half a dozen of them,” thing myself. Unfortunately, I don’t always remember to do that, and clothing manufacturing variances being what they are, often not all of them are as good.

I did find that article on SciAm’s site, but paywalled. I’ll wait. If it turns out to be significant, one of the other sites I follow will cover it.

Definitely it would be weird if pilot-wave turned out to be reality. That was the first interpretation I gravitated toward. It seemed like common sense. Until I learned about its issues. It would mean explicit non-locality. No hiding behind epistemic veils. And rethinking quantum field theory. Maybe, since most physicists don’t currently take it that seriously, it would shake things up for quantum gravity. Given how stubbornly successful QM and QFT have been, I’m not holding my breath, but the universe might surprise us.

Yeah, I don’t know the details of what Reynolds had in mind with The Absence. Given his background, I wonder if he thought it out. (It’s not a given. He had some physics in Terminal World that seemed dubious, although still a fun story.) I do think in the story that it was a consequence, not a designed effect.

What I wondered was, what happens to the light that passes through Andromeda before reaching the Milky Way? Is everything in that direction of the universe now missing? And would the effect spread as the causal effects from both galaxies spread out? What does an observer in a third galaxy see?

• Wyrd Smythe

That’s a good question. How much light from behind Andromeda reaches us as it is? If we subtracted Andromeda’s light, would any remain?

The kind of non-locality found in QM, which can’t be used to communicate information, never bothered me. It seems a necessary part of wavefunction collapse, which is a big mystery anyway. (As you likely know, I’ve got my eye on interference, superposition, and entanglement, as the potential keys to the puzzle.)

I was reminded recently (by Sabine Hossenfelder) how different “collapse” is mathematically from physically. It’s part of why I think the Schrödinger Equation might not be the whole story. Mathematically, collapse is the projection of the current wavefunction state vector onto some measurement eigenvector. This has two results; it’s the second one Hossenfelder reminded me of. Firstly, of course, the state vector suddenly aligns with the measurement eigenvector. That’s what most think of with (mathematical) collapse. But secondly, the projection, which is the probability density, doesn’t have a length of one. The non-linear adjustment collapse requires moving the vector and resizing it back to one. It’s a double whammy on the math side.

On the physical side, there’s this wave-thing. Interference tells us something wave-like is there. It apparently instantly vanishes if the particle interacts at a point location with something else that thereafter will be seen as a wave (until it’s localized by an interaction). One can sure see the attraction of the Bohmian idea that the wave-thing is some sort of non-local magic that guides the “real” particle.

[My own WAG isn’t very different. A particle in flight is just the wave, which is a diffuse coherent pattern in the appropriate quantum field. There is no particle, just energy spread out over the wave. The non-local magic is when that wave interacts with another wave at a (random? chosen by some subtle balance?) spacetime point. The energy transfer from one quantum field to the other is instant.]

• SelfAwarePatterns

You’ve been talking lately about “an interaction” causing the collapse. I wonder what you mean by that. Interaction with another particle? It seems to be implied by what you said about the wave interacting with another wave. If so, how would that square with qubits interacting with other qubits and only entangling rather than collapsing? Are we talking about a particular type of interaction? Or by an interaction, do you mean the enormous number of interactions involved with decoherence?

A single interaction does work in Rovelli’s RQM, but that’s because its collapses are only relative to the interacting entities. So the qubits, when they interact, collapse relative to each other, but not relative to an external measuring device. When the measuring device interacts with the circuit of qubits, then, for the measuring device, the entire circuit collapses. (Technically it’s collapsing relative to every particle in the measuring device, and eventually every particle in the surrounding environment.)

Is there another sense of interaction I’m missing?

• Wyrd Smythe

An interaction with another “particle” (keeping in mind “particle” always means a wave-like object). For instance, a photon is absorbed by an electron, which raises the energy level of the electron. Later that electron might drop in energy and emit a photon. Both absorbing and emitting are interactions between the electron “particle” (which is a single-quanta wavelet in the electron quantum field) and the photon “particle” (a wavelet in the EMF field). In these interaction examples, the electron persists, but the photon is destroyed or created. There are many other kinds. Any valid Feynman diagram, essentially. They all describe “particle” interactions.

The thing is, when the “particle” is in flight, not interacting at that moment, it’s a spread-out wave. Feynman diagrams are misleading in giving a sense of particle trajectories. The lines should be taken as abstractions only — just inputs, outputs, and interactions.

Entanglement, one of my three suspected keys, is the result of a special kind of interaction. For example, a spin-0 “particle” might decay into a pair of spin-1/2 “particles” — the spins of which would be fully entangled to conserve the original spin-0. Splitting a photon into two lower-frequency photons can likewise entangle their spins (polarizations).

Decoherence is likewise the result of interactions, but in kind of the opposite direction. It’s what happens as the result of lots of interactions with other quantum states. It’s the high-entropy attractor. Entanglement is a fragile low-entropy state.

Interference is easily explained because the vibration of the quantum fields really is there and really does interfere with itself when multiple paths combine.

The big mystery in this view (even accepting QM non-locality) is what selects a particular point for interaction, and how does the spread-out quantum field vibration instantly transfer to another field and shape? Einstein’s spooky action example was a photon released inside a hollow sphere with a one-foot radius. One nanosecond later the photon impacts the wall of the sphere and is absorbed by an electron in one of the atoms. But nothing in QM says where it lands, which electron absorbs it. Interference patterns tell us something extends to and touches all points of the inner wall. Something that uses complex number math. It’s what physically “collapses” — suddenly vanishes — when the wave interacts with another wave.

It’s clearly non-local. Maybe the geometry of space is weirder than we think. There are reasons people keep saying “everything is connected.” Time seems fundamental, but space could be emergent.

• SelfAwarePatterns

Thanks. I think I see where you’re coming from. But now I’m wondering what you see distinguishing interactions that lead to collapse vs interactions that only lead to entanglement. Or vs interactions that don’t appear to lead to either, such as a photon reflecting off a mirror in a quantum experiment.

The conventional answer appears to be that “which way” information has to propagate into the environment. I’m wondering if your answer here is different. Maybe another way to ask this is, can collapse happen without decoherence, in the sense of the system becoming entangled with its environment?

Definitely if there is an instantaneous physical collapse, then that’s pretty much non-local dynamics, by definition.

• Wyrd Smythe

Well, depending on what we mean by “collapse”, all interactions cause it. They all result in a sudden change to the wavefunctions of the “particles” involved. In many cases, those “particles” are destroyed or created — a more physical collapse. Those are the interactions behind what most mean by “measurement” — a “particle” is absorbed and detected. Its wavefunction not only collapses, it vanishes. (The Schrödinger equation, in fact, can’t handle particle creation and destruction; it’s about particle evolution. That’s the purview of QFT.)

There are specific types of (generally carefully managed) interactions that entangle wavefunctions. To the extent it happens naturally all around us, it almost instantly vanishes due to decoherence — due to interaction with multiple other wavefunctions. But where we can preserve it, we get non-local observations (unless one clings to the superdetermination loophole). My take is that non-locality is experimentally validated and must be, at least provisionally, accepted as fact. Given that conclusion, similar non-locality in other aspects isn’t a problem for me. I accept a non-local universe — one subject to the no-communications theorem. It does respect causality.

I’m not sure what “which way” information is exactly, so let me state it this way: A coherent system is one that preserves its phase information — the phase always evolves according to what the wavefunction says — it’s not affected (decohered) by phase information from other wavefunctions.

On its own, phase isn’t something we can detect. The global phase of a quantum system has no physical meaning. It’s when the wavefunction interacts with another wavefunction (or itself) in a superposition that the relative phase between the parts of the superposition interact. The two-slit result, of course, comes from such a superposition.

When two wavefunctions interact such that their wavefunctions merge into a single inseparable wavefunction — one that cannot be separated into two separate wavefunctions in superposition — then the two systems are entangled. They have global and relative phase. Interaction with other wavefunctions will “collapse” (i.e. change) the entanglement, in most cases destroy it.

In all cases, decoherence is the loss of phase information. It’s very much like entropy in being strongly one-way. A small system takes on the phase influences of all surrounding systems. It’s the sound of a huge crowd of voices; it completely swamps individual voices. Keeping a system coherent is really hard. You need to kick both Kelvin and Maxwell out the door.

But anyway, yeah, “collapse” (in the sense of sudden wavefunction change) can definitely happen without decoherence. One example is multiple spin measurements on the same particle. We would label the “particle” wavefunction as unknown before the first measurement, but (assuming a Z-axis measurement) is “collapsed” to either Z+ or Z- after. If, say, the Z+ “particles” go through a Y-axis measurement, the wavefunction changes to either Y+ or Y- (and is now a 50/50 superposition of the Z-axis). A third measurement station would again “collapse” the wavefunction. But the particle remains “coherent” until its actually detected. Only then does it “collapse” in the sense usually meant, and that interaction is often also the end of the particle. At the least, it localizes it.

Note that some say the particle is entangled with the spin magnets because, after passing through the field, the particle’s flight carries information about the field (strength, direction). This seems a more generic use of the term “entangled” than the mathematical one where it’s the tensor product (rather than superposition) of two wavefunctions.

• SelfAwarePatterns

Sabine Hossenfelder retweeted this. It quickly gets over my head, but I thought you might find it interesting.

• Wyrd Smythe

That’s kind of an exciting paper; I saved the PDF for later. In testing the micro-regime where theories deviate in their predictions, it’s a similar approach to the one Ananthaswamy wrote about. I’ve hope they turn up something new; I’ve wanted to see progress in QM for a long time.

(I think I read that the muon weirdness seen at CERN evaporated into the test data, but I still have some hopes for the muon weirdness in Chicago. The thing about the g-2 experiment, though, is that calculation approximation error is still a strong contender. We might be getting so good with experimental data that we’ve bumped into our ability to calculate experimental predictions.)

• SelfAwarePatterns

I think I’m still confused about all interactions causing collapse. It keeps sounding RQMish to me, but I know you’re not an RQMer. And I’m not clear how the subsequent discussion about interacting wave functions and entanglement (which matches my understanding) fits. (It’s also the end of the day and I’m fried, so it might totally be me.)

I agree that non-locality in terms of non-separability has to be accepted (unless the universe does surprise us with actual superdeterminism). But non-local dynamics, as I understand it, are tied to an objective collapse, except in Bohmian mechanics.

“Which way” was just a sloppy shorthand for referring to information like which path the particle took, or whatever is being measured. I’m still thinking about those mirrors in quantum experiments. It seems like the photon gets absorbed and then reemitted by the electrons in the mirror, but due to the properties of the material, no “which way” information get left in the mirror (or only does so very minimally).

On the spin example, do you have a link to the details of that experiment? Or remember what it was called? I remember the setup in that class, but it was a while back and the details are hazy.

On particles being entangled with magnets, something like that is usually described in a non-collapse interpretation where the entanglement never gets destroyed. Decoherence is often described as the measured system becoming entangled with the environment. My understanding is that it’s the same as entanglement between a couple of particles, but on a much larger scale, and obviously far more complex.

Hope they’re able to do that experiment sometime soon. Seems like a lot of people are probing that boundary.

• Wyrd Smythe

Well, I don’t want to pile on if it’s been a long day! We can pick it up tomorrow. Or never, if you don’t want to pursue it. For now I’ll try to be super brief. (I said I’ll try…)

First, I posted about the spin example a while back. Quantized spin was discovered in the Stern-Gerlach experiment with silver atoms, but it can be demonstrated with light and polarized filters. This post has more about it.

I suppose we could call decoherence entanglement with the environment. That is what’s happening. It’s not a very helpful entanglement, though. That crowd of tens of thousands of voices. You go from having a coherent conversation with the person you walked in with, to having hundreds of simultaneous conversations with hundreds of people around you. Helpful entanglement involves that original conversation between the two of you. (Non-locality being like having cell phones!)

Question: What do you mean by “non-local dynamics?

• SelfAwarePatterns

Thanks for the spin links. I also dug up the class notes for that Allan Adams lecture. https://ocw.mit.edu/courses/physics/8-04-quantum-physics-i-spring-2013/lecture-notes/MIT8_04S13_Lec01.pdf

This goes to show how imprecise words like “measure” and “collapse” are. Notably, the intermediate sorting between different spins. His example (page 7) includes recombining the pathways, leading to the indeterminate state returning. But that only works if we haven’t done anything to find out which path the particle took before it reaches the combiner. That, to me, seems to indicate we don’t dispense with wave mechanics until the end of the experiment, when information about the spin states propagate out into the environment, which involves decoherence. (At least that’s my current conclusion. Might be different later.)

The term “non-local dynamics” refers to action at a distance. We get that with a physical collapse interpretation. We also get it with Bohmian mechanics. We don’t get it with many-worlds, RQM, or (reportedly) consistent histories. The epistemic collapse interpretations also often claim to avoid it since they’re only talking about our local measurements, if you accept that move.

• Wyrd Smythe

Ah, excellent! That MIT 8.04 course, with Allan Adams, is the first one I watched. He’s a really fun teacher. And of all the other lecture series I’ve found, I still think it’s my favorite. The MIT 8.05 course that follows, with Barton Zwiebach, is just as good. (I watched the 2013 MIT 8.04 course Adams taught. There is also a 2016 version of MIT 8.04 taught by Zwiebach. I’ve been meaning to watch that one.)

So, you’re most excellently on the same page, dude! His Figure 5, on page 4, is exactly the three-stage experiment I’ve been referring to. (As well as what I was talking about in those QM-101 posts I linked to.) And all the experiments that follow are versions of where I’ve been taking my explanation about interaction and wavefunction “collapse” (and “measurement” or “observation”).

Many lectures later, when Adams returns to spin (using spin-1/2 particles; electrons), he tells his students that “hardness” and “color” were actually vertical and horizontal electron spin, and the boxes were essentially Stern–Gerlach devices. Similar experiments use photons as the particle and polarizers as the interaction device. They demonstrate the same phenomenon.

What’s happening on page 7 (and onto page 8) is easy to explain in terms of wavefunction interaction. The hardness box is an interaction that leaves (“collapses”) the electron’s wavefunction to a known eigenbasis. Note that the hardness eigenbasis has two eigenvectors, Hard and Soft. If we detected the electron now, it could only be in one of those two states. But so long as we can (completely) describe the electron as a superposition of these, we preserve the original quantum state.

So, on page 7, in the first case we get 50/50 and in the second only White electrons. The combine box makes the superposed states into a single state, the input state. On page 8, blocking one path destroys half the superposition “collapsing” to a Hard or Soft eigenvector. Since hardness and color are orthogonal, collapsing to a hardness eigenvector means losing all information about color.

The multi-stage experiments I’ve been discussing (as illustrated by Figure 5 on page 4) are extensions of this. The bottom line is that interactions “collapse” the wavefunction — update it in a non-linear way — but can still leave it coherent and in superposition of possible states. What we might call “ultimate collapse” comes when we localize or detect the particle. Depending on how it’s viewed, that seems to involve “spooky action at a distance.”

[A simple home experiment demonstrating quantum mechanics: Position two polarizing filters at 90° to each other so they block all the light that tries to pass through both. Note that, if positioned 0° to each other, they allow most of the light through (minus any tinting), and, if positioned 45° or other intermediate angle, they allow varying degrees of light through. Now, with two set in the 90° position and blocking all the light, insert a third filter between them angled at 45° — suddenly, where light was blocked, an additional filter allows considerable light to pass.]

• Wyrd Smythe

BTW: I don’t know if you saw (or if you did, if you care about) the more detailed discussion below. I got into it last night, got carried away, more like, so I’m not sure I’ll continue it unless there’s an interest.

• SelfAwarePatterns

I actually had missed it. Looks like you’re thinking on the page. Which I do myself at times, so I totally understand the impetus. But I’m afraid it’s too far over my head for me to provide any intelligent input.

• Wyrd Smythe

Ha! I was actually in teaching (or mansplaining) mode. This stuff is freshman QM and doesn’t take much thinking. It’s just a detailed explanation of these experiments. The impromptu sense, I’m sure, comes from writing it off the top of my head, as if we were hanging out in a bar. 🙂

I’m sure you’d find it not over your head at all, but it does take the interest and desire to get down into the weeds. Much of what’s here channels that first lecture Adams gives. These are like the two-slit interference experiments in showing us something important about the QM world.

• Wyrd Smythe

I’ll leave off on further elaboration below. I took it up through the three-stage experiment that can be replicated at home with three polarizing filters. It’s a cool demonstration that shows we can experience quantum effects in our classical world.

More importantly, to wrap this up, hopefully you see what I mean by “interaction” — an umbrella term for many kinds of wavefunction changes (“collapses” or “non-linear updates”). That part is all QM 101. The speculation on my part is that what you term “dynamic collapse” — the kind involving localizing the “particle” — isn’t that much different from the shifts due to magnetic or polarizing interactions. Both involve non-linear wavefunction updates, but it’s only when we localize or “measure” the “particle” the wavefunction represents that things get “spooky.”

I further speculate that vibrations in the quantum field — Bohm’s guiding waves — are the thing. They don’t guide a particle, they are the “particle” — its energy is spread out in that wave. That much is what QFT basically says. The speculative part is the non-local way the energy of that spread-out wave instantly transfers to a spread-out wave in a different quantum field. The vibration in the EMF field that’s the “photon” suddenly, at a certain point, becomes a vibration in the electron field that’s the “electron.” That’s definitely spooky and I have no explanation at this time.

But! 🙂 It does solve the measurement problem.

• Wyrd Smythe

I couldn’t resist one more. I meant to explore that Allan Adams experiment in terms of wavefunction interaction. I’ve done so below.

• Wyrd Smythe

Writing a detailed explanation helps solidify things in my own mind, so this can be seen as an exercise for my own sake. Feel free to join in, or not, when and if you like.

“I think I’m still confused about all interactions causing collapse.”

By which I mean that all interactions cause a non-linear change to the wavefunctions of the respective “particles” (there may be some exceptions, but I think I’m safe saying that’s the rule).

Specifically, the wavefunction state vector “collapses” to some eigenbasis according to the projections onto that eigenbasis (the length of each projection determines the probability of getting that measurement; their squares must sum to 1.00). For the wavefunction to continue to be valid, an interaction (“measurement”) involves two non-linear updates to the wavefunction. Firstly, update the state vector to the eigenvector actually measured — in other words, select that projection. Secondly, since the projections usually have lengths less than 1.0, the selected one is updated to a length of 1.0. These non-linear updates are what some see as a problem single-world non-collapse interpretations.

There are certain cases where this also involves the “collapse” of that magical quantum field that can interfere with itself and other quantum systems. And since that field seems to be real, that it suddenly vanishes is very vexing. Updating a vector is mathematical and can be dismissed as epistemic, but whatever is going on here is hard to understand. A related question is why a photon lands here and not there.

The first thing to be clear about is that localizing a “particle” — measuring its location — is a QM operation that “collapses” its wavefunction in terms of position and momentum (but may leave other quantum properties untouched). But how we localize a particle may affect them. If we absorb a photon to energize an electron on a screen, we know where that photon is. Or was. The electron has inherited its quantum properties (energy, being about it; photons are spin-0 and have no charge, so there’s nothing for the electron to conserve).

Let’s use photons and polarizing filters. The basic setup is that one photon sequentially interacts with three polarizing filters, each set at its own angle. Schematically, it looks like:

$\gamma_{0}\Rightarrow\oslash_{a}:\gamma_{1}\Rightarrow\oslash_{b}:\gamma_{2}\Rightarrow\oslash_{c}:\gamma_{3}$

With photon, gamma (γ), going through three polarizing filters a, b, and c. After passing through any filter, the photon’s wavefunction has made the non-linear change — mathematical “collapse.”

Note that we never localize the photon — its position is never measured. It could pass through a fourth device and its wavefunction would change again. The analysis is about how its wavefunction changes due to interacting with the filters.

A key point is that the four wavefunction states (γ0–3) are all superpositions.

At first, γ0, polarization is completely unknown, so we can describe it as an equal superposition of any eigenbasis. The canonical form uses the {|0⟩,|1⟩} eigenbasis:

$|\Psi\rangle_{\gamma}=\frac{1}{\sqrt{2}}\left(|{Z^{+}}\rangle+|{Z^{-}}\rangle\right)=\frac{1}{\sqrt{2}}\left(|0\rangle+|1\rangle\right)$

But it’s just as valid to say:

$|\Psi\rangle_{\gamma}=\frac{1}{\sqrt{2}}\left(|{X^{+}}\rangle+|{X^{-}}\rangle\right)=\frac{1}{\sqrt{2}}\left(|{+}\rangle+|{-}\rangle\right)$

Or:

$|\Psi\rangle_{\gamma}=\frac{1}{\sqrt{2}}\left(|{Y^{+}}\rangle+|{Y^{-}}\rangle\right)=\frac{1}{\sqrt{2}}\left(|{i+}\rangle+|{i-}\rangle\right)$

Or any other eigenbasis you care to come up with. In all cases, we’re saying there is a 50/50 chance — if we measure — of finding the polarization at any given angle. All angles, 50/50 shot the photon passes the filter.

To try to keep this from being obscenely long, I’ll stop here. That will also allow for questions or discussion about the framework and setup.

• Wyrd Smythe

Oops. The three superpositions are how we’d write it for spin-1/2 particles. It’s the same basic thing with photons but written a bit differently, like this:

$|\Psi\rangle_{\gamma_{0}}=\frac{1}{\sqrt{2}}\left(|{L}\rangle\!+\!|{R}\rangle\right)=\frac{1}{\sqrt{2}}\left(|{H}\rangle\!+\!|{V}\rangle\right)$

Same thing, different spelling. The Bloch Sphere applies in both cases.

• Wyrd Smythe

Part Two…

So, given the setup:

$\gamma_{0}\Rightarrow\oslash_{a}:\gamma_{1}\Rightarrow\oslash_{b}:\gamma_{2}\Rightarrow\oslash_{c}:\gamma_{3}$

And the initial superposition:

$|\Psi\rangle_{\gamma_{0}}=\frac{1}{\sqrt{2}}\left(|{V}\rangle+|{H}\rangle\right)$

After passing through Filter-A (if it passed through), we’ll assume the filter angle is vertical, the wavefunction collapses:

$|\Psi\rangle_{\gamma_{1}}=|{V}\rangle$

The wavefunction vector is updated to the |V⟩ eigenvector (as described previously). Note that, because of this double update, the photon passes through additional filters with the same setting with 100% probability. And fails to pass an orthogonal filter with the same certainty.

The polarization state has collapsed, but note that the photon is coherent, and we can validly describe it as a superposition of a different eigenbasis:

$|\Psi\rangle_{\gamma_{1}}=\frac{1}{\sqrt{2}}\left(|{D}\rangle+|{A}\rangle\right)$

Because this eigenbasis is orthogonal to the {|V⟩,|H⟩} eigenbasis, we know there are 50/50 odds, but that’s actually a special case. Non-orthogonal angles work, but deliver different odds because we know the polarization is vertical. The general case is:

$|\Psi\rangle_{\gamma_{1}}=\cos\!\left(\theta\right)\!|{V}\rangle+\sin\!\left(\theta\right)\!|{H}\rangle$

Where theta (θ) is the angle of the filter from the vertical. The probability of either result is the square of the cosine of the angle. In the case of the {|D⟩,|A⟩} eigenbasis, we know that the relative angle is 45°, so

$|\Psi\rangle_{\gamma_{1}}=\cos\!\left({45}^{\circ}\right)\!|{D}\rangle+\sin\!\left({45}^{\circ}\right)\!|{A}\rangle=\frac{1}{\sqrt{2}}\left(|{D}\rangle+|{A}\rangle\right)$

Which is how we got the one above. The original {|V⟩,|H⟩} eigenbasis has a zero angle to the vertical, which is why:

$|\Psi\rangle_{\gamma_{1}}=\cos(0)|{V}\rangle+\sin(0)|{H}\rangle={1.0}|{V}\rangle+{0.0}|{H}\rangle=|{V}\rangle$

Where things get interesting is after the second filter. That’s enough for this one. More later.

• Wyrd Smythe

Part Three…

In case it’s not clear, in this representation:

$\displaystyle\gamma_{0}\!\Rightarrow\!\!\oslash^{0^{\circ}}_{a}\!\!:\;\gamma_{1}\!\Rightarrow\!\!\oslash^{45^{\circ}}_{b}\!\!:\;\gamma_{2}\!\Rightarrow\!\!\oslash^{90^{\circ}}_{c}\!\!:\;\gamma_{3}$

The photon (gamma, γ) goes through (arrow) a filter (circle labeled ac). The slash signifies the filter has an angle, which is indicated in a superscript. The colon signifies the result or output, the photon (γ) in a new state (labeled 04).

Initially, we have:

$\displaystyle|\Psi\rangle_{\gamma_{0}}=\tfrac{1}{\sqrt{2}}\!\left(|{V}\rangle\!\!+\!\!|{H}\rangle\right)=\tfrac{1}{\sqrt{2}}\!\left(|{D}\rangle\!\!+\!\!|{A}\rangle\right)=\tfrac{1}{\sqrt{2}}\!\left(|{L}\rangle\!\!+\!\!|{R}\rangle\right)$

Or any other eigenbasis. We don’t know anything about the initial polarization, so there’s a 50/50 chance the photon will pass a filter at any given angle. In this case, the first filter is set to an angle of 0° and now (assuming the photon passes — 50% of them will) the wavefunction is:

$\displaystyle|\Psi\rangle_{\gamma_{1}}=|{V}\rangle=\tfrac{1}{\sqrt{2}}\!\left(|{D}\rangle\!\!+\!\!|{A}\rangle\right)=\cos\theta|{V}\rangle\!+\sin\theta|{H}\rangle$

The last version shows the general case. The key point is that the photon is still described by a superposition. The interaction with the first filter “collapses” the state vector to the |V⟩ eigenvector, but it’s still a superposition of other eigenbases. (As shown previously, it’s even still a superposition of the {|V⟩,|H⟩} eigenbasis with coefficients of 1.0 and 0.0, respectively.)

So now suppose it goes through the second filter, which we’ll say is set to 45°. This gives us the third state of the photon. If it passes the filter — the probability is:

$\displaystyle\rho_\gamma=\cos\!\left(\theta\right)^2=\cos\!\left({45}^{\circ}\right)^{2}=\left(\tfrac{1}{\sqrt{2}}\right)^{2}=\tfrac{1}{2}$

Note: This assumes the 45° angle is the same as the |D⟩ (diagonal) eigenvector. A 135° angle would match the |A⟩ (anti-diagonal) eigenvector.

The photon state is now:

$\displaystyle|\Psi\rangle_{\gamma_{2}}=|{D}\rangle=\tfrac{1}{\sqrt{2}}\!\left(|{V}\rangle\!\!+\!\!|{H}\rangle\right)=\cos\theta|{D}\rangle\!+\sin\theta|{A}\rangle$

The state vector has “collapsed” again, this time to the |D⟩ eigenvector. As before, it still can be described as a superposition, but that superposition is now relative to the |D⟩ eigenvector, not the |V⟩ one.

A key point is that we’ve lost the previous information about the |V⟩ value of γ1. If we measure the vertical axis, our results are again 50/50.

Likewise, if we measure the horizontal axis. After the first filter, there was a zero chance of γ1 passing a horizontal filter. But γ2 has a different wavefunction, one oriented at the |D⟩ eigenvector, which is 45° from the horizontal. That means, as before, the photon (γ2) now has a 50% chance of passing a horizontal filter.

Assuming it does, we have:

$\displaystyle|\Psi\rangle_{\gamma_{3}}=|{H}\rangle=\tfrac{1}{\sqrt{2}}\!\left(|{D}\rangle\!\!-\!\!|{A}\rangle\right)=\sin\theta|{V}\rangle\!+\cos\theta|{H}\rangle$

Going through the second filter gives the photon a (50%) chance of passing the third filter whereas, without the second filter, it has a 0% chance. That’s a distinctly QM result, and it can be demonstrated with three polarizing filters. And note that, once again, we’ve lost information about the diagonal and other axes.

It’s actually kind of mind-blowing. 🙂

• Wyrd Smythe

I meant to go over the experiment Allan Adams describes in his MIT 8.04 (Spring 2013) lecture notes, specifically what happens with the cases described on page 7 and page 8. I’ll try to be as succinct at possible.

Starting with Figure 9 and Figure 10 on page 7, note similar experiments but different input preparations. The first case uses Hard electrons, the second uses White ones. We obtain these starting conditions through off-stage boxes, Hardness and Color ones, respectively. Prior to that, the electrons are in an unknown “random” state (for all we know, truly random). We describe that as:

$\displaystyle|\Psi\rangle_{initial}=\tfrac{1}{\sqrt{2}}\Big(|X\rangle\!+\!|Y\rangle\Big),\;\;\;\forall\,\big\{|X\rangle,\!|Y\rangle\big\}$

Unknown electrons are a (50/50) superposition of any orthogonal basis we like. Here we have two:

$\displaystyle\epsilon_1\!=\!\big\{|White\rangle,\!|Black\rangle\big\}\!=\!\big\{|{0}\rangle,\!|{1}\rangle\big\}\\[0.3em]\epsilon_2\!=\!\big\{|Hard\rangle ,\!|Soft\rangle\big\}\! =\!\big\{|{+}\rangle,\!|{-}\rangle\big\}$

An important point: Each basis is orthogonal; its components are mutually exclusive. However, the two bases are orthogonal to each other. A measurement is either Hard or Soft (or White or Black) but measuring one or the other is also orthogonal. A key thing the experiment demonstrates is that orthogonality.

So the superposition above could be in terms of either of those. In Figure 9, the off-stage box is a Hardness box, and the experiment uses only the ones that emerge from the Hard port. So, we update the wavefunction:

$\displaystyle|\Psi\rangle_{input}=|Hard\rangle=\tfrac{1}{\sqrt{2}}\Big(|White\rangle\!+\!|Black\rangle\Big)$

It’s important to understand that, although the wavefunction has “collapsed” to Hard, it’s still also a superposition of White and Black. Likewise, in Figure 10, we have:

$\displaystyle|\Psi\rangle_{input}=|White\rangle=\tfrac{1}{\sqrt{2}}\Big(|Hard\rangle\!+\!|Soft\rangle\Big)$

And that superposition is important to understanding what happens in the experiment.

In both cases, the first stage is a Hardness box. In the first case, if we measured the electron, we’d find only Hard ones, no Soft ones. That’s because the wavefunction is already collapsed to Hard. In the second case, if we measured, we’d find a 50/50 mix of Hard/Soft, because the input state there was a superposition of those states.

When we combine the output of the first stage (the Hardness box), we regain the input state. The Color box is presented with, in the first case, Hard electrons, and in the second case, White electrons. The results are exactly what we’d expect.

The kicker comes from blocking a path before the Combine stage in the Figure 10 experiment (as shown in Figure 11 on page 8). But it’s simple to understand because after the first Hardness box we have:

$\displaystyle|\Psi\rangle_{path1}=|Hard\rangle=\tfrac{1}{\sqrt{2}}\Big(|White\rangle\!+\!|Black\rangle\Big)\\[0.25em]|\Psi\rangle_{path2}=|Soft\rangle=\tfrac{1}{\sqrt{2}}\Big(|White\rangle\!-\!|Black\rangle\Big)$

The path1 and path2 superpositions mathematically combine to result in a |White⟩ state vector (that has to be renormalized). But if either are blocked, we’re left with a superposition that the Color box splits into 50/50. Note that it’s the phase difference between the two |Black⟩ states that cancels them out. The two |White⟩ states have the same phase and reenforce (hence the need to renormalize the vector).

Bottom line, the experiment results are easily understood in terms of what the wavefunction is doing — how it evolves as the result of interacting with the boxes.

• Wyrd Smythe

I should maybe add that, if we fed Black electrons into the Hardness box, the two paths would have the |White⟩ state as out of phase and canceling and the |Black⟩ state as in phase and reenforcing.

• SelfAwarePatterns

Right. For me, the key thing here is that since the particle wave packet can be recombined afterward, it seems like the sorting inside the boxes, by themselves, don’t cause collapse. It’s what happens afterward. It’s only when information about the property being measured gets out, when its causal effects propagate into the environment, that we get the irreversible collapse, or at least the phenomenology of collapse. (Which fits with most of what I’ve read.)

• Wyrd Smythe

Perhaps a way to distinguish it is that there is an unrecoverable form of collapse when we localize the wave, an action that involves transferring some or all of that wave to another wave. Keep in mind that, physically, this usually involves absorbing the particle. Photons disappear (it’s more complicated with electrons).

But the same way the two-slit experiment demonstrates the reality of interference, these filter experiments demonstrate the reality of wavefunction change. In many regards they’re the same thing. The two parts interfere or reenforce. What’s going on there is as real as what’s going on two-slit experiments.

😀 As I’ve said, I’ve come to see superposition, interference, and entanglement, as the key mysteries. My guess is that solving those solves the package. (Note what’s not on that list: decoherence and measurement. We’re making progress on the former, and I think the latter depends on the big three.)