[tsimionescu]

No, I am not denying anything.

My point is this: say an electron emits a photon and changes speed, in perfect accordance to the standard model and QFT. I don't think it makes sense to say that the electron "computed" the energy of the photon, or its own change of speed. It just happened, there was no computation going on here.

Even in a CPU, it doesn't make sense to say that the transistors, or even logical gates, are "computing" how much electricity passes through them. The entire system of transistors arranged into logical gates arranged into a processor is doing computation of the program written in memory, but the subcomponents are only following the simple laws of physics.

In a quantum computer, the same is true - the computer itself may be running Shor'a algorithm, but each individual qubit is simply doing the few things that the laws of physics allow it to do.

[thom]

I think the argument is more that the electron and photon are subjective interpretations of the observable consequence of some computation, not that they are computing things in and of themselves.

[3g4o53g4o5]

Thanks this is exactly what I am trying to say.

We dont know exactly how the universe is doing or how the photons do to themselves, but by doing experiments, scientists figured out the law of computiation of this vague "universe computer" a.k.a laws of physics.

And since scientist's discovery do not violate the actually behavior of the physical world, there established a isomorphism. And the very same law is used in quantum computing, mainly, in chemistry. And everything success and predictable. It is a successful scientific theory. Under this notion, it is nothing wrong to say that the quantum world is doing some kind of computation underneath because it is the current understanding of how the universe works.

[tsimionescu]

To my mind, I think that if you want to say that the universe is a computer, then you can't say it's doing linear algebra, even though the behavior of particles is described by linear algebra.

If you want to model the universe as a computer, than its basic operations are the interactions described in the Standard Model, and the symbols it works on are particles&fields that exist. But the universe computer is not resolving a linear algebra equation to decide what happens when an electron emits a photon. Instead, the electron emitting a photon with some energy etc. is one of the elementary operations of the universe computer.

Coming back to the CPU example, a basic operation in a CPU is setting a bit to 1. That operation is not divisible into any other more elementary operations from the point of view of modeling the physical CPU as a computer. Of course, there are other physical phenomena going down to the SM that are the realization of this basic operation, but those are not part of the modeling: the CPU computer, as a model, works by flipping bits.

Similarly, for QM, the universe computer works by doing one of the possible interactions from the standard model. As far as we know, there is no layer of detail underneath this, even if the interactions of the standard model are indeed linear algebra.

One important way in which saying "the universe is computing linear algebra" is wrong is that, as far as we know, the universe is instantly calculating the solutions of the linear equations - the electron doesn't go into an "emitting" state, then emit a photon with the appropriate values some time later after the computation is finished.

[3g4o53g4o5]

Bascially your assumption is that something that looks and works like an Intel CPU carry out an operation, that can be called a computation, everything else is not. But sorry this is not the only method to "compute". You are limiting the definition of computiation and try too hard to justify all false assumption that you have been made.

[tsimionescu]

My assumption is that something like a Turing machine, or like a reduction in Lambda calculus, or like a demonstration with the basic laws of predicate logic (all known equivalent models of computation) is a computer.

[tsimionescu]

Ok then, what is the computer running that computation, and what are the symbols it is manipulating to produce the movement of the electron and photon?

(I am assuming you are not referring to human knowledge of the electron or photon, which - if we accept that consciousness is computational - is obviously the result of a computation in our brains).

[thom]

I have no idea, I’m just saying you can conceive of physical phenomena being the subjective experience of existing within a computed environment. If, on the other hand, the computation happens within the physical substrate of the thing it’s computing… that seems weird to me.

[3g4o53g4o5]

Well. FYI, unitary transformation, creation and annihilation operator, etc.

[tsimionescu]

Are these physical objects? Do they have mass, energy, volume, a position or speed, charge, color charge, weak hyper charge, spin etc?

[3g4o53g4o5]

The operation of adding and subtracting per se in classical computers also lacking these physical properties. If you use this as your counterargument, namely classical computer can compute without the inherent operation owning a physical property, then you left yourself with no ground of saying that quantum computing is invalid. You better check your logic.