5 ms·

Schrödinger’s Cat When Nobody Is Looking

60 points by pmjoyce 6y ago

mannykannot 6y ago
This article contains a consise explanation of the black hole information paradox, and, for the first time, I feel as though I understand what the issue is (assuming that it is not glossing over some important issues.)
deleted 6y ago
[deleted]
rkagerer 6y ago
One of the problems is that quantum theory is obscure (to say the least) regarding what it claims about the nature of the world when no one is looking. Is the involvement of a consciousness required for the theory to make sense, and if so, does that include a mouse’s or a fly’s? In particular, the specification of what constitutes a measurement is irreparably vague. Perhaps all that’s needed is a large enough apparatus. But what’s large enough? And what happens at the boundary? These issues are referred to as the measurement problem. In my utterly uninformed imagination I've reconciled this by defining observation as the point where the observer (whether it be a simple apparatus like the sensor on a photon counter, or a complex and squishy one like my consciousness) becomes "intertwined" with the observation. i.e. Once the information has reached some particle, that particle's view of the waveform/event has collapsed. It's easy to forget the actual conveyance of the information has some physical manifestation (photons hitting my retina, electrons bumping against transistors in an IC and eventually manifesting as dots on a screen which send out those photons) and I picture those causal steps as propogating constraints through the universe. Light speed sets a maximal boundary on how much of the universe may be "intertwined" with the observable, but even if the data is sitting on the computer next to me, until I take a peek (or otherwise subject myself to any consequences stemming from them) those constraints haven't yet permeated any of the bits of the universe that make up me. Akin to how relativity permits two different observers to hold differing views of some phenomena (eg. silmultanaety) this worldview allows me to imagine the cat is both dead and alive even though my computer or the Geiger counter may know the correct answer. I'd love to hear from real quantum physicists whether this interpretation is bunk or has some validity (and if so, whether someone else arrived at it before me and gave the theory a name).
- monktastic1 6y ago
  IANAQP, but your view comes close to Rovelli's Relational QM. It may not be entirely precise to say that your computer knows the "correct" answer -- it just know its answer. Yours still does not exist. Once you know your answer, its answer "becomes" correct (because you must agree). (Of course, given that the very existence of the Geiger counter or computer may depend on which branch occurred (perhaps there was a bomb on one path?), it's unclear whether you are free to think of there even being an "it" that could have an answer, either.)
  - pdonis 6y ago
    > the very existence of the Geiger counter or computer may depend on which branch occurred (perhaps there was a bomb on one path?) At the quantum level, the quantum degrees of freedom in the Geiger counter or the computer still exist even if a bomb goes off. They just have a different relationship in terms of interactions than they would if the bomb didn't go off.
    - monktastic1 6y ago
      Sure, something has recorded the state. It's just that we like to think of there being fixed, discrete entities that have knowledge, whereas really it's more like that knowledge is an integral part of their identity.
- GoblinSlayer 6y ago
  Everett proposed relativistic interpretation. The measurement happens solely due to physical interaction and is properly contained in light cone. The difference is that the cat has two states: one dead and one alive, when you physically interact with them, your state splits into two, each state sees the respective cat's state, both are real, but the picture is relative. The observation corresponds to not what exists, but to what physical interactions happen, and because these split states don't interact, they don't see each other as if it was a collapse.
- FartyMcFarter 6y ago
  I'm far from being an expert, but does your interpretation allow for quantum computation to work? Sounds neat if it does.
hleszek 6y ago
So, I am missing something, how does it work with the double slit experiment ? the result should never act as a wave without observation if we have spontaneous collapse all the time ? Or is this spontaneous collapse quite rare in practice ?
- lisper 6y ago
  Yes, that's right. Extremely rare. The only reason that the theory works at all is that a single spontaneous collapse can propagate throughout a complex system of entanglements and collapse the whole system. The nice thing about spontaneous collapse is that it makes a testable prediction: there should be a scale at which the behavior of an isolated system starts to show divergence from quantum predictions. So far that prediction has failed to be demonstrated, but people are still working on it.
- pdonis 6y ago
  > is this spontaneous collapse quite rare in practice ? It's extremely rare for a simple quantum system like a single electron; but it is happening basically all the time for a very large system like the detector in the double slit experiment. So basically, the electron is virtually certain to get all the way through the double slit experiment without any spontaneous collapse, but as soon as it interacts with the detector screen at the end of the experiment it will have to collapse basically immediately, because the detector screen is always having spontaneous collapse events and the electron is now entangled with the screen and has to collapse along with it.
TheOtherHobbes 6y ago
This seems like a reinvention of the Penrose Interpretation. https://en.wikipedia.org/wiki/Penrose_interpretation https://en.wikipedia.org/wiki/Penrose_interpretation
- guerrilla 6y ago
  Both are collapse theories [1][2], but presumably not identical being that the author is aware of Penrose's work and credits Penrose earlier in the article for some terminology as well as acknowledging his influence on the theory in the following footnote form the article: > 6. In this, we have been strongly influenced by considerations in this regard made over 3 decades ago by works such as Penrose, R. Time asymmetry and quantum gravity. In Isham, C.J., Penrose, R., & Sciama, D.W. (Eds.) Quantum Gravity II (1981); Wald, R.M. Quantum gravity and time reversibility. Physical Review D 21, 2742 (1980). The first footnote tells us that the author is referring to GWR theory [3] specifically (which is distinct from Penrose's): > 1. Ghirardi, G.C., Rimini, A., & Weber, T. Unified dynamics for microscopic and macroscopic systems. Physical Review D 34, 470-491 (1986); Pearle, P. Combining stochastic dynamical state-vector reduction with spontaneous localization. Physical Review A 39, 2277-2289 (1989); for a relatively recent review see Bassi, A. & Ghirardi, G. Dynamical reduction models. Physics Reports 379, 257-426 (2003). 1. https://en.wikipedia.org/wiki/Objective-collapse_theory https://en.wikipedia.org/wiki/Objective-collapse_theory 2. https://plato.stanford.edu/entries/qm-collapse/ https://plato.stanford.edu/entries/qm-collapse/ 3. https://en.wikipedia.org/wiki/Ghirardi%E2%80%93Rimini%E2%80%93Weber_theory https://en.wikipedia.org/wiki/Ghirardi%E2%80%93Rimini%E2%80%...
galaxyLogic 6y ago
This is a good new theory which makes SENSE as far as I can understand. But, if we apply Occam's Razor then isn't the explanation to all quantum weirdness simply that we live in a simulated universe?

60 points by pmjoyce 6y ago

This article contains a consise explanation of the black hole information paradox, and, for the first time, I feel as though I understand what the issue is (assuming that it is not glossing over some important issues.)

deleted 6y ago

[deleted]

rkagerer 6y ago

One of the problems is that quantum theory is obscure (to say the least) regarding what it claims about the nature of the world when no one is looking. Is the involvement of a consciousness required for the theory to make sense, and if so, does that include a mouse’s or a fly’s? In particular, the specification of what constitutes a measurement is irreparably vague. Perhaps all that’s needed is a large enough apparatus. But what’s large enough? And what happens at the boundary? These issues are referred to as the measurement problem. In my utterly uninformed imagination I've reconciled this by defining observation as the point where the observer (whether it be a simple apparatus like the sensor on a photon counter, or a complex and squishy one like my consciousness) becomes "intertwined" with the observation. i.e. Once the information has reached some particle, that particle's view of the waveform/event has collapsed. It's easy to forget the actual conveyance of the information has some physical manifestation (photons hitting my retina, electrons bumping against transistors in an IC and eventually manifesting as dots on a screen which send out those photons) and I picture those causal steps as propogating constraints through the universe. Light speed sets a maximal boundary on how much of the universe may be "intertwined" with the observable, but even if the data is sitting on the computer next to me, until I take a peek (or otherwise subject myself to any consequences stemming from them) those constraints haven't yet permeated any of the bits of the universe that make up me. Akin to how relativity permits two different observers to hold differing views of some phenomena (eg. silmultanaety) this worldview allows me to imagine the cat is both dead and alive even though my computer or the Geiger counter may know the correct answer. I'd love to hear from real quantum physicists whether this interpretation is bunk or has some validity (and if so, whether someone else arrived at it before me and gave the theory a name).

monktastic1 6y ago
IANAQP, but your view comes close to Rovelli's Relational QM. It may not be entirely precise to say that your computer knows the "correct" answer -- it just know its answer. Yours still does not exist. Once you know your answer, its answer "becomes" correct (because you must agree). (Of course, given that the very existence of the Geiger counter or computer may depend on which branch occurred (perhaps there was a bomb on one path?), it's unclear whether you are free to think of there even being an "it" that could have an answer, either.)
- pdonis 6y ago
  > the very existence of the Geiger counter or computer may depend on which branch occurred (perhaps there was a bomb on one path?) At the quantum level, the quantum degrees of freedom in the Geiger counter or the computer still exist even if a bomb goes off. They just have a different relationship in terms of interactions than they would if the bomb didn't go off.
  - monktastic1 6y ago
    Sure, something has recorded the state. It's just that we like to think of there being fixed, discrete entities that have knowledge, whereas really it's more like that knowledge is an integral part of their identity.
GoblinSlayer 6y ago
Everett proposed relativistic interpretation. The measurement happens solely due to physical interaction and is properly contained in light cone. The difference is that the cat has two states: one dead and one alive, when you physically interact with them, your state splits into two, each state sees the respective cat's state, both are real, but the picture is relative. The observation corresponds to not what exists, but to what physical interactions happen, and because these split states don't interact, they don't see each other as if it was a collapse.
FartyMcFarter 6y ago
I'm far from being an expert, but does your interpretation allow for quantum computation to work? Sounds neat if it does.

hleszek 6y ago

So, I am missing something, how does it work with the double slit experiment ? the result should never act as a wave without observation if we have spontaneous collapse all the time ? Or is this spontaneous collapse quite rare in practice ?

lisper 6y ago
Yes, that's right. Extremely rare. The only reason that the theory works at all is that a single spontaneous collapse can propagate throughout a complex system of entanglements and collapse the whole system. The nice thing about spontaneous collapse is that it makes a testable prediction: there should be a scale at which the behavior of an isolated system starts to show divergence from quantum predictions. So far that prediction has failed to be demonstrated, but people are still working on it.
pdonis 6y ago
> is this spontaneous collapse quite rare in practice ? It's extremely rare for a simple quantum system like a single electron; but it is happening basically all the time for a very large system like the detector in the double slit experiment. So basically, the electron is virtually certain to get all the way through the double slit experiment without any spontaneous collapse, but as soon as it interacts with the detector screen at the end of the experiment it will have to collapse basically immediately, because the detector screen is always having spontaneous collapse events and the electron is now entangled with the screen and has to collapse along with it.

TheOtherHobbes 6y ago

This seems like a reinvention of the Penrose Interpretation. https://en.wikipedia.org/wiki/Penrose_interpretation https://en.wikipedia.org/wiki/Penrose_interpretation

guerrilla 6y ago
Both are collapse theories [1][2], but presumably not identical being that the author is aware of Penrose's work and credits Penrose earlier in the article for some terminology as well as acknowledging his influence on the theory in the following footnote form the article: > 6. In this, we have been strongly influenced by considerations in this regard made over 3 decades ago by works such as Penrose, R. Time asymmetry and quantum gravity. In Isham, C.J., Penrose, R., & Sciama, D.W. (Eds.) Quantum Gravity II (1981); Wald, R.M. Quantum gravity and time reversibility. Physical Review D 21, 2742 (1980). The first footnote tells us that the author is referring to GWR theory [3] specifically (which is distinct from Penrose's): > 1. Ghirardi, G.C., Rimini, A., & Weber, T. Unified dynamics for microscopic and macroscopic systems. Physical Review D 34, 470-491 (1986); Pearle, P. Combining stochastic dynamical state-vector reduction with spontaneous localization. Physical Review A 39, 2277-2289 (1989); for a relatively recent review see Bassi, A. & Ghirardi, G. Dynamical reduction models. Physics Reports 379, 257-426 (2003). 1. https://en.wikipedia.org/wiki/Objective-collapse_theory https://en.wikipedia.org/wiki/Objective-collapse_theory 2. https://plato.stanford.edu/entries/qm-collapse/ https://plato.stanford.edu/entries/qm-collapse/ 3. https://en.wikipedia.org/wiki/Ghirardi%E2%80%93Rimini%E2%80%93Weber_theory https://en.wikipedia.org/wiki/Ghirardi%E2%80%93Rimini%E2%80%...

galaxyLogic 6y ago

This is a good new theory which makes SENSE as far as I can understand. But, if we apply Occam's Razor then isn't the explanation to all quantum weirdness simply that we live in a simulated universe?