6 ms·

I'm betting that someone will prove a TANSTAAFL theorem for Quantum computing. In other words, you might be able to factor in polynomial steps, but each step wi

by gluejar 17y ago

I'm betting that someone will prove a TANSTAAFL theorem for Quantum computing. In other words, you might be able to factor in polynomial steps, but each step will take time proportional to the size of your Hilbert space.

Estragon 17y ago
I'm betting that the Copenhagen interpretation of the Quantum mechanics formalism is false. There is no empirical basis for it, and it is a fundamentally pessimistic view of physics (that we don't know certain things because we simply can't know them.) I don't think the superpositions in the quantum mechanical formalism reflect any objective reality, their just a standard statistical reflection of our ignorance of the system's total state. But the notion of quantum computation crucially depends on these superpositions. To me the vast efficiency gains claimed for quantum computation are actually a reductio ad adsurdum for the Copenhagen interpretation accordiing objective reality to these superpositions. That people are apparently attempting serious implementations of quantum computation is very exciting to me, because it means these ideas are going to be severely tested soon.
- Herring 17y ago
  Bell's theorem demands that you give up locality or realism. Either is fine; historically speaking it's just been easier to give up realism. Of course physicists found a way to keep both (by splitting the observer up), & MWI's increasing popularity reflects this. In my view it's useless to argue about interpretations. Last I checked they had the same predictions.
  - Estragon 17y ago
    In my view it's useless to argue about interpretations. Last I checked they had the same predictions. Not true at all. If the superposition in the QM formalism merely represents our ignorance about the system's state, rather than an objective reality, then QC loses the massive parallelism which is supposed to make it so much more efficient than classical computation.
    - Herring 17y ago
      Well nobody argues the wave function represents our ignorance about the system's state. It's certainly not in the Copenhagen interpretation anyway. The wave function sacrifices realism.
      - Estragon 17y ago
        In the Copenhagen interpretation, the wave function represents our ignorance of what the system's state will become when observed, but it's taken as an accurate description of the system's actual state prior to observation. That is the point of the "Schroedinger's cat" paradox: that under the Copenhagen interpretation, the cat actually is in a superposition of alive and dead states, until someone looks in the box. Quantum computation crucially depends on the objective reality of this superposition. It seems likely to me that the superposition in the formalism actually just represents our ignorance of the system's state, not the state itself.
        Herring 17y ago
        > It seems likely to me that the superposition in the formalism actually just represents our ignorance of the system's state, not the state itself. Again, nobody argues that. It's possible to experimentally distinguish between the two situations (Bell's theorem). This is a bit of a strawman. Besides the wave function is a complex vector. It can't represent ignorance. You have to take |ψ|2 to get a real value.

by gluejar 17y ago

Estragon 17y ago

I'm betting that the Copenhagen interpretation of the Quantum mechanics formalism is false. There is no empirical basis for it, and it is a fundamentally pessimistic view of physics (that we don't know certain things because we simply can't know them.) I don't think the superpositions in the quantum mechanical formalism reflect any objective reality, their just a standard statistical reflection of our ignorance of the system's total state. But the notion of quantum computation crucially depends on these superpositions. To me the vast efficiency gains claimed for quantum computation are actually a reductio ad adsurdum for the Copenhagen interpretation accordiing objective reality to these superpositions. That people are apparently attempting serious implementations of quantum computation is very exciting to me, because it means these ideas are going to be severely tested soon.

Herring 17y ago
Bell's theorem demands that you give up locality or realism. Either is fine; historically speaking it's just been easier to give up realism. Of course physicists found a way to keep both (by splitting the observer up), & MWI's increasing popularity reflects this. In my view it's useless to argue about interpretations. Last I checked they had the same predictions.
- Estragon 17y ago
  In my view it's useless to argue about interpretations. Last I checked they had the same predictions. Not true at all. If the superposition in the QM formalism merely represents our ignorance about the system's state, rather than an objective reality, then QC loses the massive parallelism which is supposed to make it so much more efficient than classical computation.
  - Herring 17y ago
    Well nobody argues the wave function represents our ignorance about the system's state. It's certainly not in the Copenhagen interpretation anyway. The wave function sacrifices realism.
    - Estragon 17y ago
      In the Copenhagen interpretation, the wave function represents our ignorance of what the system's state will become when observed, but it's taken as an accurate description of the system's actual state prior to observation. That is the point of the "Schroedinger's cat" paradox: that under the Copenhagen interpretation, the cat actually is in a superposition of alive and dead states, until someone looks in the box. Quantum computation crucially depends on the objective reality of this superposition. It seems likely to me that the superposition in the formalism actually just represents our ignorance of the system's state, not the state itself.
      - Herring 17y ago
        > It seems likely to me that the superposition in the formalism actually just represents our ignorance of the system's state, not the state itself. Again, nobody argues that. It's possible to experimentally distinguish between the two situations (Bell's theorem). This is a bit of a strawman. Besides the wave function is a complex vector. It can't represent ignorance. You have to take |ψ|2 to get a real value.