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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
by comicjk 10y ago
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.
- Vraxx 10y agoI 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.
- comicjk 10y agoThe 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.
- wolfgke 10y ago> 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 https://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory > http://plato.stanford.edu/entries/qm-bohm/ http://plato.stanford.edu/entries/qm-bohm/ > http://plato.stanford.edu/entries/qm-decoherence/#PilWavThe http://plato.stanford.edu/entries/qm-decoherence/#PilWavThe
- OscarCunningham 10y agoYeah 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.
- davorak 10y ago> 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.
- wolfgke 10y ago> 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%93Bohm_theory&oldid=740277352#Non-equivalence 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 http://www.ejtp.com/articles/ejtpv13i35p1.pdf
- OscarCunningham 10y agoThe 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!
- 21 10y ago"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.
- comicjk 10y agoYes, 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.
- mikermcneil 10y agoIf 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.
- deleted 10y ago[deleted]