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Physicists provide support for retrocausal quantum theory

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Re: Physicists provide support for retrocausal quantum theory

#41

Earlier quoted context omitted.

Explain the double slit experiment to me. The single photon somehow calculates the interference pattern with photons that don't exist, in our world at least. If there's not parallel universes, how does a single atom calculate that interference pattern? Where do those calculations occur? All other theories say it happens by magic and give all sorts of complicated non-real obfuscations to explain it.

Bohmian mechanics seems like a better explanation than "there are infinite universes out there"

I'm sure you could confuse the heck out of me trying to explain it. Deutsch would say it's just a clever obfuscation of what's really happening. And his many-worlds explanation is so incredibly simple that my small mind uses Occam's razor to figure out what to believe.

Re: Physicists provide support for retrocausal quantum theory

#42
This reminds me a lot of the sci-fi novel Anathem by Neal Stephenson. Trying to be spoiler-free as possible, in the book, the many-worlds interpretation of quantum mechanics is the correct one, and the worlds lie on a directed acyclic graph, meaning that the flow of information can only move in one direction along the universes. So in the same way information can only travel in one direction in time (into the future), information can only travel laterally into other dimensions in one direction. So, in the book, nobody can directly influence the past, but the question of existing in multiple worlds and sending information between them, and thereby potentially exploring many possible outcomes of a situation simulatenously, is much more open.

In other words, retrocausality WITH information transfer is possible when the information is flowing from one universe to another, in a certain direction.

Re: Physicists provide support for retrocausal quantum theory

#43
post #35

// WARN: because past is static, to support retrocausal influence, we're spawning alternative universes which are joined on retrocausal action choice - this slows down The Simulation and, if abused, can exhaust resources and crash.

don't remind me that people actually believe that you can infer the existence of a simulation only with data points that are created and controlled by it.

Simulation part was a joke.

But the static, unchangeable past is interesting because: 1. assumption that the past is static and can't change is not crazy and if retrocausal influence exists, it could imply Many Worlds interpretation as more plausible - there must be at least 2 different universes with static past if you can choose at present past A or past B.

The joke is that branching universes creates large overhead costs (n unmerged, binary branches create 2^n universes to keep track of) in simulation that can crash it.

Re: Physicists provide support for retrocausal quantum theory

#44
post #31

The many-worlds interpretation of quantum mechanics is the only one that's easy to understand. All others seem to bend over backwards to realistically explain quantum effects. It's so rare to find clear explanations, but they do exist. My favorite from David Deutsch, a main creator of the idea of quantum computing: To those who still cling to a single-universe world-view, I issue this challenge: explain how Shor’s al…

> My favorite from David Deutsch, a main creator of the idea of quantum computing: It's interesting, but this "I challenge you to answer a philosophical (not scientific) question in a way that I find acceptable" approach surely skirts uncomfortably close to dogmatically creationist arguments. (For the record, my answer, which certainly wouldn't satisfy Deutsch, is: it works because the math proves it works; there's n…

Math is used to explain the universe. It isn't an explanation in of itself.

We never progressed anywhere by saying "something just works" and leaving it at that. Challenge yourself.

Re: Physicists provide support for retrocausal quantum theory

#45

Earlier quoted context omitted.

Explain the double slit experiment to me. The single photon somehow calculates the interference pattern with photons that don't exist, in our world at least. If there's not parallel universes, how does a single atom calculate that interference pattern? Where do those calculations occur? All other theories say it happens by magic and give all sorts of complicated non-real obfuscations to explain it.

Bohmian mechanics seems like a better explanation than "there are infinite universes out there"

Yes, I find the whole "Explain this in any other way!" sort of a bizarre demand. You've got your choice of 5 or 6 decent isomorphic explanations. Preference for "many worlds" seems to boil down to "it annoys my common sense less than some of the others", which is a very personal concern rather than a scientific one.

Personally, I actually think retrocausality, once you twist your brain around it, is another perfectly sensible option that doesn't involve multiplying the universe into a near-infinity of inaccessible, unobservable parallels. The solution in my mind is that retrocausality actually isn't; what it means instead is that what "the present" is is even less like what you thought it was, and is even more of a partial order than relativity already told us it was. The answer to the "double-slit" experiment, to my mind, is that there simply isn't a "before" and "after" and some sort of "retrocausal self-interference" of the wave... the whole thing is simply one atomic event that doesn't have a before and an after, and your imposition of a temporal order on the events is much simplified from the reality. The mystery lies in your attempt to impose a global temporal order, which is appropriate enough at scale, onto a single local event where it doesn't apply in the way you expect. The results of the double-slit experiment itself is not that mysterious, merely counterintuitive, once you release the small scale from your imposed large-scale idea of how time flows.

It means that "the present" is actually quite complicated in a quantum universe with as many qubits as ours has, but, just as QM may be counterintuitive but eventually looks classical at a large enough scale, time may in fact be massively complicated but at scale it still works as we expect.

Re: Physicists provide support for retrocausal quantum theory

#46
post #24

Earlier quoted context omitted.

That seems to be begging the question. Qubits do more than this universe is capable of, therefore there must be multiple universes. The obvious refutation is: qubits don't do more than this universe is capable of, because the universe does not run on classical limits. 10^80 atoms implying on the order of 10^80 computations that can be done implicitly assumes that these things operate on classical-ish rules. There's a…

Explain the double slit experiment to me. The single photon somehow calculates the interference pattern with photons that don't exist, in our world at least. If there's not parallel universes, how does a single atom calculate that interference pattern? Where do those calculations occur? All other theories say it happens by magic and give all sorts of complicated non-real obfuscations to explain it.

There are no photons. There are only photon-like events, with associated probabilities and scattering processes.

It's a lot easier to assume that reality is the visible output of an heroically counter-intuitive but relatively tractable probabilistic calculation process, than it is to assume there are infinite universes with poorly defined boundary conditions between them and even more poorly defined properties, and that by some magical process some, or maybe all, of those universes conspire together in certain situations only to create quantum effects.

The Shor's Algorithm argument is irrelevant. There's a huge leap between saying saying "Qubits can handle superpositions and we don't know why yet" and saying "The only possible explanation is that qubits exist in multiple universes at the same time. Because they just have to. Obviously."

The problem is simple - you're inventing entire multiple universes out of nothing just to explain the behaviour of a single qubit.

That may indeed be how reality works. but it's a very strong claim and it needs some correspondingly irrefutable evidence to support it.

Re: Physicists provide support for retrocausal quantum theory

#47
post #24

Earlier quoted context omitted.

That seems to be begging the question. Qubits do more than this universe is capable of, therefore there must be multiple universes. The obvious refutation is: qubits don't do more than this universe is capable of, because the universe does not run on classical limits. 10^80 atoms implying on the order of 10^80 computations that can be done implicitly assumes that these things operate on classical-ish rules. There's a…

Explain the double slit experiment to me. The single photon somehow calculates the interference pattern with photons that don't exist, in our world at least. If there's not parallel universes, how does a single atom calculate that interference pattern? Where do those calculations occur? All other theories say it happens by magic and give all sorts of complicated non-real obfuscations to explain it.

The atom is a wave, which can interfere with itself.

Re: Physicists provide support for retrocausal quantum theory

#48
post #37

Earlier quoted context omitted.

You didn't defend Deutsch's erroneous assumption that atoms are responsible for physical interactions in computation. Even in quantum computing atoms are not responsible for any computation––especially if you have a system like DWave which uses magnetically induced currents. "The natural computational abilities of reality itself" Additionally you continue to insist that computation is a real physical thing. Are you c…

Take the interference pattern built in the famous double slit experiment: what Deutsch and other recognized is that there's computation happening to create that pattern. And similar computation is present in all quantum effects. Quantum computers in effect harness that natural computational power. I don't fully understand how, but Deutsch proved that you can create a general computing machine from those natural quant…

You continue to ignore the weak points of Deutsch's argument that I've pointed out.

You can create a computing machine by assigning physical states to any physical behavior, quantum, classical, hamiltonian, etc. The proof is trivial and it is not a proof he came up with.

It further follows, there is no computation happening during the creation of an interference pattern until we assign it our own abstract semantic states.

This quantum woo is helping neither science nor quantum physics; in fact you are hindering it. Ascribing causal responsibility to non-observable (explicitly unknowable)† entities used to be criticized as dogmatic dribble, now it's embraced as popular science meant only to provoke reaction. Science is about establishing useful models of the world to make physical predictions.

† See common fallacy: https://en.wikipedia.org/wiki/Ontological_argument

Re: Physicists provide support for retrocausal quantum theory

#49

Earlier quoted context omitted.

Explain the double slit experiment to me. The single photon somehow calculates the interference pattern with photons that don't exist, in our world at least. If there's not parallel universes, how does a single atom calculate that interference pattern? Where do those calculations occur? All other theories say it happens by magic and give all sorts of complicated non-real obfuscations to explain it.

Bohmian mechanics seems like a better explanation than "there are infinite universes out there"

Bohmian mechanics is just many worlds in denial, for people with prior ontological beliefs they can't give up.

The entire wave-function is there in the theory, containing all the "worlds" and it's responsible for 100% of the dynamics.

Additionally, Bohmians add a single "world particle" indicating which world we are in, and it's guided by the wavefunction. They claim only that particle is "real", but since it has no effect on the state of the universe, I would call it the only part of the theory which isn't real.

Re: Physicists provide support for retrocausal quantum theory

#50

Earlier quoted context omitted.

Explain the double slit experiment to me. The single photon somehow calculates the interference pattern with photons that don't exist, in our world at least. If there's not parallel universes, how does a single atom calculate that interference pattern? Where do those calculations occur? All other theories say it happens by magic and give all sorts of complicated non-real obfuscations to explain it.

There are no photons. There are only photon-like events, with associated probabilities and scattering processes. It's a lot easier to assume that reality is the visible output of an heroically counter-intuitive but relatively tractable probabilistic calculation process, than it is to assume there are infinite universes with poorly defined boundary conditions between them and even more poorly defined properties, and t…

That's exactly what I'm saying! All other explanations say something confusing and obfuscating like "there are no photons". Many-worlds keeps it simple and says "there are photons, and the reason they behave like that is because they're interacting with parallel universes". You can't explain why they behave like that, so you say that the photon isn't really real, and have a complicated explanation of it.
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