I’m not sure of what exactly you’re after with this question, or what the question would even mean.
Any Turing-equivalent model seems equally valid.
In my mind, “a machine computed X” means that we can use the machine to figure out the answer to X. For instance, John Searle claims that any physical process can be interpreted to instantiate any computation, given a complex enough interpretation. According to this view, e.g. an arbitrary wall can be said to be computing 2+2 as well as 583403 + 573493. But the flaw here is that you cannot actually use the wall to tell you the answer to 583403 + 573493. If you already know the answer, you can come up with a contrived mapping of the wall’s atoms to a computation giving the result, but then you cannot use this mapping to tell you the result to any other calculation. So “the machine computed 2+2″ means that after the computation, the machine was in such a state that you could somehow read “2+2 = 4” from its state.
“Computing red” means that a system has an internal representation of the external world, where a specific kind of sensory data produced by the eyes (or equivalent sensors) is coded as being that specific type. This coding is subjectively experienced as the color red.
The intermediate steps matter. A giant look-up table wouldn’t be conscious, though the process that originally produced the table could be.
I have no idea of what a physical theory explaining consciousness would be like. So I don’t know.
See above.
Only certain kinds, though I’m unsure of the exact properties required.
I’m not sure of what exactly you’re after with this question, or what the question would even mean.
Any Turing-equivalent model seems equally valid.
In my mind, “a machine computed X” means that we can use the machine to figure out the answer to X. For instance, John Searle claims that any physical process can be interpreted to instantiate any computation, given a complex enough interpretation. According to this view, e.g. an arbitrary wall can be said to be computing 2+2 as well as 583403 + 573493. But the flaw here is that you cannot actually use the wall to tell you the answer to 583403 + 573493. If you already know the answer, you can come up with a contrived mapping of the wall’s atoms to a computation giving the result, but then you cannot use this mapping to tell you the result to any other calculation. So “the machine computed 2+2″ means that after the computation, the machine was in such a state that you could somehow read “2+2 = 4” from its state.
“Computing red” means that a system has an internal representation of the external world, where a specific kind of sensory data produced by the eyes (or equivalent sensors) is coded as being that specific type. This coding is subjectively experienced as the color red.
The intermediate steps matter. A giant look-up table wouldn’t be conscious, though the process that originally produced the table could be.
I have no idea of what a physical theory explaining consciousness would be like. So I don’t know.
See above.
Only certain kinds, though I’m unsure of the exact properties required.