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Comment by lossolo | Hacker News Reader

I would be surprised if we are not living in simulation. Look at superposition and function collapse in quantum physics, it's equivalent to what we are doing in games today = do not render if player is not watching, save resources. Think about it, look for example at GTA V, what we can achieve today and think about how world looked like 100 years ago.

I imagine that in 1000 years from now, simulating world similar to ours will not be a problem at all. Maybe not as complex because every level you go deeper you have less resources at your disposal. Who knows which level deep we are? Maybe we are simulation in simulation in simulation...

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This is a common misconception, but superposition has nothing to do with "do not render if the player is not watching." As far as we know, every particle in the universe is interacting with every other (with a light speed delay) and thus "measuring" it (modifying and responding to its wavefunction) at all times. In the two-slit experiment, for example, the wavefunction of a particle moving through a slit interacts with the wavefunction of the particle used to detect it, causing both wavefunctions to be more narrowly distributed in the space around the slit. But before or after this interaction, the whole wavefunction still needs to be simulated to produce the effects we see experimentally. The wavefunction itself is the real thing being simulated, and it's always "running."

You may be right that it will become easier to simulate worlds like ours, but it will require innovations that make a quantum computer look like an etch-a-sketch. The universe is really big and really detailed.

I see the distinction you're making (I think), but I still don't see how that invalidates GP's analogy. Surely "running" a wavefunction is computationally cheaper than re-evaluating the particle's characteristics at every universal frame. Perhaps it's not so much about our own "watching" but rather "do not calculate when irrelevant". My own analogy might be an online map frame like google maps, where tiles outside the viewing box are not loaded. This is because we can tell what needs to be calculated by the bounding box of the viewer without needing all the other finer details. I see it more as a lazy eval.

The particle's characteristics ARE the wavefunction - or to say it another way, the wavefunction is the only real characteristic a particle has.

When I run a quantum mechanics simulation at work, I might afterwards calculate the particle positions or some other classical characteristic of the system. But I need those characteristics only because I'm trying to get a classical model of the system. The system itself, when it's running, doesn't do any of that. It interacts wavefunction-to-wavefunction. As far as we know, that's how the universe works.

> The particle's characteristics ARE the wavefunction - or to say it another way, the wavefunction is the only real characteristic a particle has.

As far as I know not in the De-Broglie-Bohm theory (but I'm not a physicist, so correct me if I'm wrong):

> https://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory

> http://plato.stanford.edu/entries/qm-bohm/

> http://plato.stanford.edu/entries/qm-decoherence/#PilWavThe

Yeah you're right, but in the De Broglie-Bohm theory the wavefunction is calculated, and then the movements of the particles are calculated on top. So from a computational perspective it's strictly harder.

> As far as I know not in the De-Broglie-Bohm theory

As a physicist I am telling you should not conclude that the De-Broglie-Bohm theory is tell you anything different than what comicjk said.

> The particle's characteristics ARE the wavefunction

This kind of statement is normally said to stress the fact that the best evidence and experiments indicate quantum mechanics accurately describe the physical world and even parts like superposition(single particle double slit experiment, tunneling etc) that defy more classical intuitions.

De-Broglie-Bohm theory includes the same set of non-intuitive behaviors that all valid interpretations of quantum mechanics have, in other words it is not testable different from other interpretations.

> De-Broglie-Bohm theory includes the same set of non-intuitive behaviors that all valid interpretations of quantum mechanics have, in other words it is not testable different from other interpretations.

There exist opinions that disagree:

> https://en.wikipedia.org/w/index.php?title=De_Broglie%E2%80%...

"In 2016, Pisin Chen and Hagen Kleinert argued that the Copenhagen interpretation and the De Broglie–Bohm theory yield different results for the ratio of peak intensities in the double-slit experiment. They concluded that they are thus not mathematically equivalent."

> http://www.ejtp.com/articles/ejtpv13i35p1.pdf

Thanks for the citation, I had not seen that recent paper(2016).

Pisin Chen and Hagen Kleinert say that De-Broglie-Bohm theory does not agree with experimental results or the rest of quantum mechanics.

This is surprising since there evidence of this is from a 1979 paper, their citation [15]

[15] C. Philippidis, C. Dewdney and B. J. Hiley, Il Nuovo Cimento 52B, 15 (1979)

can be found online(republished) at: http://www.pbx-brasil.com/FisQuan/Notas/Area01/semana041/pap...

I would want to do some additional research before agreeing with Pisin Chen and Hagen Kleinert that the De-Broglie-Bohm theory has been experimentally disproven.

Other then combining the existing research double checking the numerical simulation and algorithms in [15] would be my approach.

Pisin Chen and Hagen Kleinert paper seems to lack such an examination which would have made for a more conclusive argument.

Is it possible that the calculations you are performing afterwards are what is causing the waveform interactions to have definitive results? In other words, could the waveform interactions cause the waveforms to become coupled and cause the entire system to exist in a superposition until such time as a classical measurement is made?

The computational problem of simulating a wavefunction is suspected by computer scientists to be exponentially harder than simulating classical physics (this is the question of whether BPP=BQP). So quantum physics is the opposite of a computational optimisation!

"really big" and "really detailed" is relative.

We have no absolute scale to measure against. Our 10^80 particle universe (or whatever the number is) could live in an 10^8000 particle one.

So our whole universe could literally be contained in something as "big" as a grain of sand in the host universe.

Yes, I'm referring to big and detailed relative to what we can simulate with foreseeable technology. Sure, we can see how to maybe simulate a universe the size of a cell, and a much much larger universe could maybe simulate everything in ours. But in either case, the larger universe is going to view the smaller one as a simplification.

If I'm running Linux in a VM, I don't think of it as a simplification-- but it is way easier to just shut it off and reinstall if something goes wrong.

I'm not sure I buy into that, because we haven't been able to draw a strict line between what a "player" and "npc" would potentially be.

Players = gods. NPC = rest of us.

The players are those lucky few that have an internal voice and their own agency. They can do almost whatever they want, as long as they can figure out how.

NPCs are more like walking zombies and have to fill the role they were born into.

How do you explain that some algorithms are provably faster on quantum computers than classical computers, if quantum is merely an optimization?

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