Experiments spell doom for physical-collapse explanation of quantum weirdness • Hacker News Board

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#161

Post by plutonorm » Fri, Oct 21, 2022, 6:28 PM UTC

criddell wrote: post #24

dzdt wrote: post #4

There is an often-repeated statement that different quantum mechanical theories are equivalent. This is an over-simplification. Is wave function collapse is a real thing or just an approximation of what happens when a large system is entangled? Some smart people have tried to make theories where wave function collapse is a real thing. These new experiments are working to rule out those ideas. My feeling is that Evere…

> My feeling is that Everett's "many worlds" interpretation is the clear favorite But what are the worlds? My feeling is that Max Tegmark has it right. Everything is mathematics.

Just go full Idealism. All things that can be - just are. A block universe, of all possible things and all possible interrelation of things. A giant timeless crystal of qualia. It's pretty obvious to me now.

One location in the latent space of a latent diffusion model is a view into a universe that is as real as ours. That half cat, half dog monstrosity you accidentally created. It exists as a drawing, or as a physical mass of flesh, with every possible back story as to how it got there. And also every possible future.

edit- brain fart

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#162

Post by GoblinSlayer » Fri, Oct 21, 2022, 6:29 PM UTC

pdonis wrote: post #119

TheOtherHobbes wrote: post #96

Earlier quoted context omitted.

You don't think postulating an unknown number of extra universes with a very poorly defined relationship with each other qualifies as an extra assumption?

The MWI does not postulate extra universes, although that pop science description is unfortunately common even though it is wrong. The MWI just says that the one universe that exists is actually very, very different from what we perceive. (To be clear, I'm not saying this correct description makes the MWI any more palatable. I am just clarifying exactly what kind of unpalatableness the MWI requires.)

We perceived flat earth and geocentrism, so not the first time. I can recommend quantum electrodynamics to people who are too attached to corpuscular paradigm.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#163

Post by GoblinSlayer » Fri, Oct 21, 2022, 6:33 PM UTC

ryeights wrote: post #158

pdonis wrote: post #119

Earlier quoted context omitted.

The MWI does not postulate extra universes, although that pop science description is unfortunately common even though it is wrong. The MWI just says that the one universe that exists is actually very, very different from what we perceive. (To be clear, I'm not saying this correct description makes the MWI any more palatable. I am just clarifying exactly what kind of unpalatableness the MWI requires.)

Can you elaborate on this? The Wikipedia page for MWI says >The many-worlds interpretation implies that there are most likely an uncountably infinite number of universes. https://en.wikipedia.org/wiki/Many-worlds_interpretation

Those worlds are states in superposition, the term "world" is an allegory to help people understand that those states don't interact due to linearity of the Schrodinger equation, because not all properties of linearity are obvious.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#164

Post by simonh » Fri, Oct 21, 2022, 6:34 PM UTC

plutonorm wrote: post #157

jfengel wrote: post #144

Earlier quoted context omitted.

No. They don't behave at all like dark matter. Among other things, there's no reason for them to be distributed in a halo, nor for some galaxies to lack them.

Broad statements, do you have the time to elaborate?

Dark matter affects some galaxies, but the rotation of others is completely explained by the observable matter. Why would one galaxy be influenced by its many worlds twins, but not another?

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#165

Post by geertj » Fri, Oct 21, 2022, 6:35 PM UTC

pdonis wrote: post #115

iainmerrick wrote: post #58

Earlier quoted context omitted.

I have never fully understood that idea, even after reading Hossenfelder's posts about it. The idea that there's a "block universe" and everything is predetermined is comprehensible, sure; but what's the exact mechanism by which Bell's inequality is violated in experiments? Doesn't that require the universe to have been carefully set up to look as if it's acting in a weird non-local way, on an experiment-by-experimen…

> Doesn't that require the universe to have been carefully set up to look as if it's acting in a weird non-local way, on an experiment-by-experiment basis? Yes. That is a big reason why most physicists do not favor superdeterminism.

I am not so sure. In my understanding of the block universe, causality doesn't really exist, and the universe is simply a consistent solution with boundary conditions both at the beginning and at the end of time (as well as in space).

The game of life is perhaps a nice analogy here. On the 2d grid of the game of life, a glider seems moving in a certain direction when time moves forward. But in the 3d grid, where time is the third dimension, a glider is just a static volume of space.

The reason we experience time is that the evolution of the block universe does depend on the dimension you look at (e.g entropy generally increases in the positive time dimension), and because our consciousness is an emergent property of a self-sustaining structure within the block universe, it's plausible at least that we perceive movement in time different from movement in space. I realize this is very sloppy wording but I'm having trouble finding better words to describe my intuition here.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#166

Post by pdonis » Fri, Oct 21, 2022, 6:35 PM UTC

ryeights wrote: post #158

pdonis wrote: post #119

Earlier quoted context omitted.

The MWI does not postulate extra universes, although that pop science description is unfortunately common even though it is wrong. The MWI just says that the one universe that exists is actually very, very different from what we perceive. (To be clear, I'm not saying this correct description makes the MWI any more palatable. I am just clarifying exactly what kind of unpalatableness the MWI requires.)

Can you elaborate on this? The Wikipedia page for MWI says >The many-worlds interpretation implies that there are most likely an uncountably infinite number of universes. https://en.wikipedia.org/wiki/Many-worlds_interpretation

One should not be trying to learn physics from Wikipedia, particularly not for something as complicated as QM, even more particularly not for an aspect of QM as contentious as the MWI.

The MWI says that there is one single universal wave function, which evolves in time by unitary evolution forever, and that that universal wave function is all that exists. That is one universe, not an infinity of them. It is just one universe that is nothing like what we think we perceive.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#167

Post by macintux » Fri, Oct 21, 2022, 6:36 PM UTC

sillysaurusx wrote: post #159

Replying to a now-deleted comment: > Is there a good ... idiots guide to interpretation of quantum weirdness ? I am more than a little lost I’ve got you covered. And believe it or not, you’ll be joining Tiktok University today: https://www.tiktok.com/t/ZTRHqk6MP/ Tiktok has been quietly amassing a huge library of educational content, and I’ve been diligently sorting those into collections. I’ll post several more rela…

Perhaps a GitHub gist? I have a few collections that I share here that way.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#168

Post by pdonis » Fri, Oct 21, 2022, 6:36 PM UTC

GoblinSlayer wrote: post #152

pdonis wrote: post #118

Earlier quoted context omitted.

> this decomposition is called decoherence, where a classical state splits into a superposition of several different classical states. No, that's not what decoherence is. Decoherence is the spread of entanglement over a very large number of untrackable degrees of freedom (usually referred to as the "environment"). This makes interference effects unobservable. But decoherence itself does not involve any "splitting"; t…

AFAIK the largest molecule to show quantum behavior in experiments is somewhere at 100 atoms. I suppose that's all "environment" you need for a large number of degrees of freedom. And yes, spread of entanglement does mean splitting. Entangled state is not factorizable, because all states in it are split. This splitting is the result of splitting of the initial state.

> I suppose that's all "environment" you need for a large number of degrees of freedom.

No. The 100 atoms is the largest molecule that we can do experiments on without having decoherence happen and ruining our attempts to observe interference.

The number of degrees of freedom in the environment is many orders of magnitude larger, something like 10^30 or more for a typical experiment.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#169

Post by pdonis » Fri, Oct 21, 2022, 6:38 PM UTC

geertj wrote: post #165

pdonis wrote: post #115

Earlier quoted context omitted.

> Doesn't that require the universe to have been carefully set up to look as if it's acting in a weird non-local way, on an experiment-by-experiment basis? Yes. That is a big reason why most physicists do not favor superdeterminism.

I am not so sure. In my understanding of the block universe, causality doesn't really exist, and the universe is simply a consistent solution with boundary conditions both at the beginning and at the end of time (as well as in space). The game of life is perhaps a nice analogy here. On the 2d grid of the game of life, a glider seems moving in a certain direction when time moves forward. But in the 3d grid, where time…

> In my understanding of the block universe, causality doesn't really exist

That's one way of interpreting it, but superdeterminism does not entail or require this. Superdeterminism can be formulated just fine for a universe that evolves in time from some initial state according to causal processes.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#170

Post by EamonnMR » Fri, Oct 21, 2022, 6:40 PM UTC

herdcall wrote: post #54

dzdt wrote: post #4

There is an often-repeated statement that different quantum mechanical theories are equivalent. This is an over-simplification. Is wave function collapse is a real thing or just an approximation of what happens when a large system is entangled? Some smart people have tried to make theories where wave function collapse is a real thing. These new experiments are working to rule out those ideas. My feeling is that Evere…

Check out "superdeterminism," first proposed by Bell (of Bell's inequality fame) himself and currently being vigorously pursued by Sabina Hossenfelder. There is no "collapse" per se according to this model and everything is really classical with hidden variables, and the entanglement comes because everything shared the same origin (the big bang). A very fascinating and in my opinion the best explanation, though it's…

The notion that a probabilistic world enables free will in a way that a deterministic one doesn't still confuses me. A coin I flip isn't exercising free will.