Physicists provide support for retrocausal quantum theory • Hacker News Board

Re: Physicists provide support for retrocausal quantum theory

#21

Post by opportune » Thu, Jul 06, 2017, 2:04 PM UTC

ridewinter wrote: post #15

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…

What if collapsing quantum wave functions simply eliminates the possible futures within our universe in which the computation is incorrect? In that case it's not exactly a multiple-universe problem, and more an issue of imposing constraints on our own single universe.

I find this view to make much more sense than the multiple universe view. Those other universes would need the infrastructure to support the same computation, and would also need to be somehow linked to our own. Or perhaps I am misunderstanding you, and we are both saying the same thing.

Re: Physicists provide support for retrocausal quantum theory

#22

Post by emeraldd » Thu, Jul 06, 2017, 2:06 PM UTC

woliveirajr wrote: post #11

> First, to clarify (...) It does not mean that signals can be communicated from the future to the past(...) instead, retrocausality means (... it) can influence the properties of that particle (or another particle) in the past, even before the experimenter made their choice. In other words, a decision made in the present can influence something in the past. So, hard to explain in layman words: future can't transmit…

Based on that description would this sounds like an action in the present is putting constraints on a seemingly unrelated event that has an enforced but currently unobservable relationship in the future. Or something like that. Why do I get the feeling that this starts requiring higher dimensions?

Additionally: If any particle in an entangled system get's measured along the full course of it's "enforced relationship into the future" that would be the point where the system collapses.

And that's where I'd run into issues .... It would seem a more reasonable explanation that retro-causal relationships would be a fourth physical dimension for the relationship to exist along ... hmmm

Re: Physicists provide support for retrocausal quantum theory

#23

Post by petters » Thu, Jul 06, 2017, 2:07 PM UTC

pron wrote: post #17

ridewinter wrote: post #15

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…

I don't understand David Deutsch's philosophical justification. Is he suggesting that quantum computing steals computational resources from other universes? If so, in this "quantum computing as theft" view, aren't many of those universes (those similar to ours, doing a similar computation at the same time) stealing computational resources from ours at the same time, yielding the original question again?

The "different universes" in the multiverse are still parts of the same wavefunction. Therefore they can interact.

It's just that after decoherence, they will never interact again and will stay separate.

Re: Physicists provide support for retrocausal quantum theory

#24

Post by mikeash » Thu, Jul 06, 2017, 2:10 PM UTC

ridewinter wrote: post #15

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…

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 an implicit notion of "a computation" in there, which is assumed to be something roughly like what a standard computer is able to do in a standard machine instruction. What if, instead, the fundamental operations that the universe works on are things like Hadamard transforms?

Re: Physicists provide support for retrocausal quantum theory

#25

Post by steven777400 » Thu, Jul 06, 2017, 2:10 PM UTC

ridewinter wrote: post #15

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…

What about the interpretation that if reality is a computer simulation, certain operations (such as the factoring described) are a form of a security weakness in the simulation, allowing the simulation to "escape" and access/consume host computational resources?

Re: Physicists provide support for retrocausal quantum theory

#26

Post by ethn » Thu, Jul 06, 2017, 2:11 PM UTC

ridewinter wrote: post #15

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…

First if you can measure it then it must be in ~physical reality~. If we are directly interacting with it why even consider it to be in another universe? Is my keyboard also in another universe?

Second, since when is one atom responsible for a computation? In modern electronics no atom is responsible at all for computation, only the electrons are†. Even then, computation is an emergent property, computation itself is abstract and cannot be physical; but it emerges from physical interactions.

† Not even the electrons are directly, it's the energy propagated by the electrons!Hence why electronics are instant while the speed of an electron is a few cm a second

Re: Physicists provide support for retrocausal quantum theory

#27

Post by ridewinter » Thu, Jul 06, 2017, 2:11 PM UTC

opportune wrote: post #21

ridewinter wrote: post #15

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…

What if collapsing quantum wave functions simply eliminates the possible futures within our universe in which the computation is incorrect? In that case it's not exactly a multiple-universe problem, and more an issue of imposing constraints on our own single universe. I find this view to make much more sense than the multiple universe view. Those other universes would need the infrastructure to support the same compu…

Well the calculations to do this elimination would have to happen somewhere. Deutsch and the many-worlds interpretation says it happens in parallel universes. And what makes quantum computing so difficult is that you have to arrange those parallel universes to be identical in every way except the inside of the computer itself. That's the only way to get an answer back. If there's interference with the outside environment, the universes become different outside of the computer and you can't get an answer back.

I love this stuff.

Re: Physicists provide support for retrocausal quantum theory

#28

Post by rf15 » Thu, Jul 06, 2017, 2:14 PM UTC

naasking wrote: post #7

rf15 wrote: post #6

This would allow us to predict the future and potentially allow for time travel as well. Seems unlikely from the implications alone, but let's see what peer review of the details will tell us.

> This would allow us to predict the future and potentially allow for time travel as well. It doesn't actually, they discuss this in the article. The laws of thermodynamics impose an arrow of time via boundary conditions, and something similar would apply here.

True. I also like the implication that we have another proof against T-symmetry.

Re: Physicists provide support for retrocausal quantum theory

#29

Post by rf15 » Thu, Jul 06, 2017, 2:15 PM UTC

roywiggins wrote: post #8

rf15 wrote: post #6

This would allow us to predict the future and potentially allow for time travel as well. Seems unlikely from the implications alone, but let's see what peer review of the details will tell us.

Entanglement would too, if it allowed superluminal communication in the classical sense. But, it doesn't- you can't use entanglement to send information, even if there is a spooky interaction at a distance. Retrocausality would probably work in the same way.

good comparison, sure sounds like entanglement in parts

Re: Physicists provide support for retrocausal quantum theory

#30

Post by ridewinter » Thu, Jul 06, 2017, 2:16 PM UTC

ethn wrote: post #26

ridewinter wrote: post #15

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…

First if you can measure it then it must be in ~physical reality~. If we are directly interacting with it why even consider it to be in another universe? Is my keyboard also in another universe? Second, since when is one atom responsible for a computation? In modern electronics no atom is responsible at all for computation, only the electrons are†. Even then, computation is an emergent property, computation itself is…

The coolness of quantum computing is that it harnesses the natural computational abilities of reality itself. So a single atom is doing an amazing number of quantum calculations at any moment. These guys like Deutsch figured out how to harness those calculations.

And the only way to interact with parallel universes is if they are totally identical except what's inside of the quantum computer itself. Deutsch posits that the quantum computer essentially proves many-worlds.