Everything computable by a quantum computer is computable by a classical computer (only slower, in some cases). Even if the human brain does in fact do some quantum calculations, a corresponding classical brain could be made. If you really believe that functionalism requires dualism, then I do not see how quantum mechanics can possibly help.
I’m bothered by the fact that you speak of modeling brains with fMRI. fMRI tracks blood flow, not neural activity (they are correlated). It will not be useful AFAIK for scanning a brain at the neuronal level, and we will (most likely) have to map every neural connection before we’d be able to emulate a brain. Speaking of “coarse-grained neurocomputational states” may be nonsensical; we don’t know how much of the brain we’ll have to emulate to get it right.
Lastly, my recollection from back when I went searching for evidence that the brain was a quantum computer in a feeble and ultimately doomed attempt to maintain my belief in dualism, is that it was very unlikely that the brain used quantum computation.
The role of quantum mechanics in this argument is not to transcend Turing-equivalence. The role of quantum mechanics is to provide a rationale for an ontology containing entities which are fundamental yet have complex states, something which is necessary if you don’t want to think of the mind as a non-fundamental state machine. Entangled states as actual states is not absolutely the only way to do this—e.g. there are plenty of topological structures, potentially playing a role in physics, which are complex unities—but it’s a natural candidate.
I see I way overestimated the resolution of fMRI: it’s of the order of a cubic millimeter, and a cubic millimeter contains about a billion synapses! So even with a really long time series, any model you make is probably going to be pretty crappy—it’ll reproduce what your experimental subjects did in the precise situations under which they were scanned, but any other situation is liable to produce something bad.
I meant neuronal states described in a way that is coarse-grained with respect to fundamental physical degrees of freedom.
The standard argument against quantum biology of any sort is that living matter is at room temperature and so everything decoheres. One of the reasons that microtubules are attractive, for someone interested in quantum biology, is that they have some of the right properties to be storing topological quantum entanglement, which is especially robust. It would still be a huge leap from that to what I’m talking about, because I’m saying the whole conscious mind is a single quantum entity, so if it’s based on collective excitations of electrons in microtubules (for example), we would still require some way for electrons in different microtubules to be coherently coupled. Any serious attempt in this direction will also have to study the cellular and intercellular medium from a condensed-matter perspective, to see if there are any collective quantum effects, e.g. in the ambient electromagnetic field on subcellular scales, or in the form of phonons in the fibrous intra- and intercellular matrix, which could help to mediate such a coupling.
The role of quantum mechanics is to provide a rationale for an ontology containing entities which are fundamental yet have complex states, something which is necessary if you don’t want to think of the mind as a non-fundamental state machine.
Why don’t you want to think of the mind as non-fundamental? Sounds like rationalization.
The role of quantum mechanics is to provide a rationale for an ontology containing entities which are fundamental yet have complex states, something which is necessary if you don’t want to think of the mind as a non-fundamental state machine.
I don’t understand how a quantum computer satisfies this requirement, but not a classical computer.
Everything computable by a quantum computer is computable by a classical computer (only slower, in some cases). Even if the human brain does in fact do some quantum calculations, a corresponding classical brain could be made. If you really believe that functionalism requires dualism, then I do not see how quantum mechanics can possibly help.
I’m bothered by the fact that you speak of modeling brains with fMRI. fMRI tracks blood flow, not neural activity (they are correlated). It will not be useful AFAIK for scanning a brain at the neuronal level, and we will (most likely) have to map every neural connection before we’d be able to emulate a brain. Speaking of “coarse-grained neurocomputational states” may be nonsensical; we don’t know how much of the brain we’ll have to emulate to get it right.
Lastly, my recollection from back when I went searching for evidence that the brain was a quantum computer in a feeble and ultimately doomed attempt to maintain my belief in dualism, is that it was very unlikely that the brain used quantum computation.
The role of quantum mechanics in this argument is not to transcend Turing-equivalence. The role of quantum mechanics is to provide a rationale for an ontology containing entities which are fundamental yet have complex states, something which is necessary if you don’t want to think of the mind as a non-fundamental state machine. Entangled states as actual states is not absolutely the only way to do this—e.g. there are plenty of topological structures, potentially playing a role in physics, which are complex unities—but it’s a natural candidate.
I see I way overestimated the resolution of fMRI: it’s of the order of a cubic millimeter, and a cubic millimeter contains about a billion synapses! So even with a really long time series, any model you make is probably going to be pretty crappy—it’ll reproduce what your experimental subjects did in the precise situations under which they were scanned, but any other situation is liable to produce something bad.
I meant neuronal states described in a way that is coarse-grained with respect to fundamental physical degrees of freedom.
The standard argument against quantum biology of any sort is that living matter is at room temperature and so everything decoheres. One of the reasons that microtubules are attractive, for someone interested in quantum biology, is that they have some of the right properties to be storing topological quantum entanglement, which is especially robust. It would still be a huge leap from that to what I’m talking about, because I’m saying the whole conscious mind is a single quantum entity, so if it’s based on collective excitations of electrons in microtubules (for example), we would still require some way for electrons in different microtubules to be coherently coupled. Any serious attempt in this direction will also have to study the cellular and intercellular medium from a condensed-matter perspective, to see if there are any collective quantum effects, e.g. in the ambient electromagnetic field on subcellular scales, or in the form of phonons in the fibrous intra- and intercellular matrix, which could help to mediate such a coupling.
Why don’t you want to think of the mind as non-fundamental? Sounds like rationalization.
I don’t understand how a quantum computer satisfies this requirement, but not a classical computer.