Having (almost) finished the Quantum Physics sequence since this last comment, and come to the point at which this particular assignment is referred to, I figured I’d post my final conclusion here before ‘looking at the answer’, as it were.
Given a basic understanding of QM, and further understanding that macroscopic phenomenon are an extension of those same principles…
Knowing that nothing ‘epiphenomenal’ is relevant to the question of consciousness…
And assuming that no previously unobserved micro-phenomenon is responsible for consciousness, by virtue of the fact that even if there were, there is, at present, no reason to privilege that particular hypothesis...
There’s no question left. What we call consciousness is simply our view of the algorithm from the inside. I believe that I have free will because it seems like the choices I make change the future I find myself in… but there are a great many other factors implicit in my thinking before I even arrive at the point of making a choice, and the fact that the probabilities involved in defining that future are impossible to calculate under existing technology does not mean that such a feat will never be possible.
That said, even full knowledge of the state of a given brain would not allow you to predict it’s output in advance, as even in isolation, that brain would divide into a very large number of possible states every instant, and QM proves that there is no way of determining, in advance, which state that brain will arrive at at any given time. This is not randomness, per se… given sufficient information, and isolation from contaminating entanglements, one could theoretically plot out a map of possible states, and assign probabilities to them, and have reasonable expectations of finding that mind in the predicted states after a determined time… but could never be certain of finding any given result after any amount of time.
That doesn’t mean that I don’t have control over my actions, or that my perception of consciousness is an illusion… what it does mean is that I run on the same laws of physics as anything else, and the algorithms that comprise my awareness are not specially privileged to ignore or supersede those laws. Realizing this fact is no reason to do anything drastic or strange… this is the way that things have been all along, and my acknowledgment of it doesn’t detract from the reality of my experiences. I could believe that my actions are determined by chance instead of choice, but that would neither be useful, nor entirely true. Whatever the factors that go into the operation of my cognitive algorithms, they ultimately add up to me. Given this, I might still believe that I have free will… while at the same time knowing that the question itself does not have the meaning I thought it had before I seriously considered the question.
That said, even full knowledge of the state of a given brain would not allow you to predict it’s output in advance, as even in isolation, that brain would divide into a very large number of possible states every instant, and QM proves that there is no way of determining, in advance, which state that brain will arrive at at any given time.
This is not a problem. A computer runs a program the same way in almost all future outcomes, weighed by probability. QM shows how to determine what happens even in cases where it’s not as simple as that.
Do neurons operate at the quantum level? I thought they were large enough to have full decoherance throughout the brain, and thus no quantum uncertainty, meaning we could predict this particular version of your brain perfectly if we could account for the state and linkages of every neuron.
Or do neurons leverage quantum coherence in their operation?
I was once involved in a research of single ion channels, and here is my best understanding of the role of QM in biology.
There are no entanglement effects whatsoever, due to extremely fast decoherence, however, there are pervasive quantum tunneling effects involved in every biochemical process. The latter is enough to preclude exact prediction.
Recall that it is impossible to predict when a particular radioactive atom will decay. Similarly, it is impossible to predict exactly when a particular ion channel molecule will switch its state from open to closed and vice versa, as this involves tunneling through a potential barrier. Given that virtually every process in neurons is based on ion channels opening and closing, this is more than enough.
To summarize, tunneling is as effective in creating quantum uncertainty as decoherence, so you don’t need decoherence to make precise modeling impossible.
Quantum uncertainty is decoherence. All decoherence is uncertainty. All uncertainty is decoherence. If it’s impossible to predict the exact time of tunneling, that means amplitude is going to multiple branches, which, when they entangle with a larger system, decohere.
If it’s impossible to predict the exact time of tunneling, that means amplitude is going to multiple branches, which, when they entangle with a larger system, decohere.
That is not quite the conventional meaning of decoherence, though. Of course, if I recall from your QM sequence, it is, indeed, yours. Let me explain what I think the difference is between the two phenomena: a spin measurement and the tuneling process.
During an interaction such as spin measurement, a factorized state of a quantum system becomes entangled with the (quantum) state of the classical system as some of the terms in the product state decay away (according to Zurek, anyhow). The remaining “pointer” states correspond to what is usually termed “different worlds” in the MWI model. I believe that this is your interpretation of the model, as well.
Now, consider radioactive decay, or, to simplify it, a similar process: relaxation process of an excited atom to its ground state, resulting in an emission of a photon. This particular problem (spontaneous emission) requires QFT, since the number of particles is conserved in QM (though Albert Einstein was the first to analyze it). Specifically, the product state of an excited atom and the ground (vacuum) state of the electromagnetic field evolves into a ground state of the atom and an excited state of the field (well, one of almost infinitely many excited states of the field, the “almost” part being due to the Planck-scale cutoff). There is virtually no chance of the original state to reappear, as it occupies almost zero volume in the phase space (this phase space includes space, momentum, position, spin, etc.). I believe even time is a part of it.
To call radioactive decay “decoherence”, one would have to identify the ground state of the field (electromagnetic vacuum) with the classical system that “measures” the excited atom. Calling a vacuum state a classical system seems like a bit of a stretch.
An alternative approach is that the measurement happens when an emitted photon is actually detected by some (classical) external environment, or when the atom’s state is measured directly by some other means.
I am not sure if there is a way to distinguish between the two experimentally. For example, Anton Zeilinger showed that hot fullerene molecules self-interfere less than cold ones, due to the emission of “soft photons” (i.e. radiating heat). His explanation is that the emitted radiation causes decoherence of the fullerene molecule’s factorized state, due to the interaction with the (unspecified) environment, and hotter molecules emit shorter-wave radiation, thus constraining the molecule’s position (sorry, I cannot find the relevant citation).
If you identify each of the branches in the MWI model with each possible excited state of the electromagnetic field, you would have to assume that the worlds keep splitting away forever, as all possible (measured) emission times must happen somewhere. This is even more of a stretch than calling the vacuum state a classical system.
Feel free to correct me if I misunderstood your point of view.
Interesting! I hadn’t thought about quantum tunneling as a source of uncertainty (mainly because I don’t understand it very well—my understanding of QM is very tenuous).
You don’t need macroscopic quantum entanglement to get uncertainty. Local operations (chemical reactions, say) could depend on quantum events that happen differently on different branches of the outcome, leading to different thoughts in a brain, where there’s not enough redundancy to overcome them (for example, I’ll always conclude that 6*7=42, but I might give different estimates of population of Australia on different branches following the question). I’m not sure this actually happens, but I expect it does...
I’m not sure I understand how quantum events could have an appreciable effect on chemical reactions once decoherance has occurred. Could you point me somewhere with more information? It’s very possible I misunderstood a sequence, especially the QM sequence.
I could also see giving different estimates for the population of Australia for slightly different versions of your brain, but I would think you would give different estimates given the same neuron configuration and starting conditions extremely rarely (that is, run the test a thousand times on molecule for molecule identical brains and you might answer it differently once, and I feel like that is being extremely generous).
Honestly I would think the decoherance would be so huge by the time you got up to the size of individual cells that it would be very difficult to get any meaningful uncertainty. That is to say, quantum events might be generating a constant stream of alternate universe brains, but for every brain that is functionally different from yours there would be trillions and trillions of brains that are functionally identical.
If you include electrons a single water molecule has 64 quarks, and many of the proteins and lipids our cells are made of have thousands of atoms per molecule and therefore tens of thousands of quarks. I am having a hard time envisioning anything less than hundreds of quarks in a molecule doing enough to change the way that molecule would have hooked into its target receptor, and further that another of the same molecule wouldn’t have simply hooked into the receptor in its place and performed the identical function. There may be some slight differences in the way individual molecules work, but you would need hundreds to thousands of molecules doing something different to cause a single neuron to fire differently (and consequently millions of quarks), and I’m not sure a single neuron firing differently is necessarily enough for your estimate of Australia to change (though it would have a noticeable effect given enough time, a la the butterfly effect). The amount of decoherance here is just staggering.
To summarize what I’m saying, you’d need at least hundreds of quarks per molecule zigging instead of zagging in order for it to behave differently enough to have any meaningful effect and probably at least a few hundred molecules per neuron to alter when/how/if that neuron fires, or whether or not the next neuron’s dendrite receives the chemical signal. I would think such a scenario would be extremely rare, even with the 100 billion or so neurons and 100 trillion or so synapses in the brain.
You may be right, I don’t really know what’s involved in chemical reactions. A chemist knowing enough theory of a physicist would likely be able to reliably resolve this question. Maybe you really know the answer, but I don’t know enough to be able to evaluate what you wrote...
Following up...
Having (almost) finished the Quantum Physics sequence since this last comment, and come to the point at which this particular assignment is referred to, I figured I’d post my final conclusion here before ‘looking at the answer’, as it were.
Given a basic understanding of QM, and further understanding that macroscopic phenomenon are an extension of those same principles… Knowing that nothing ‘epiphenomenal’ is relevant to the question of consciousness… And assuming that no previously unobserved micro-phenomenon is responsible for consciousness, by virtue of the fact that even if there were, there is, at present, no reason to privilege that particular hypothesis...
There’s no question left. What we call consciousness is simply our view of the algorithm from the inside. I believe that I have free will because it seems like the choices I make change the future I find myself in… but there are a great many other factors implicit in my thinking before I even arrive at the point of making a choice, and the fact that the probabilities involved in defining that future are impossible to calculate under existing technology does not mean that such a feat will never be possible.
That said, even full knowledge of the state of a given brain would not allow you to predict it’s output in advance, as even in isolation, that brain would divide into a very large number of possible states every instant, and QM proves that there is no way of determining, in advance, which state that brain will arrive at at any given time. This is not randomness, per se… given sufficient information, and isolation from contaminating entanglements, one could theoretically plot out a map of possible states, and assign probabilities to them, and have reasonable expectations of finding that mind in the predicted states after a determined time… but could never be certain of finding any given result after any amount of time.
That doesn’t mean that I don’t have control over my actions, or that my perception of consciousness is an illusion… what it does mean is that I run on the same laws of physics as anything else, and the algorithms that comprise my awareness are not specially privileged to ignore or supersede those laws. Realizing this fact is no reason to do anything drastic or strange… this is the way that things have been all along, and my acknowledgment of it doesn’t detract from the reality of my experiences. I could believe that my actions are determined by chance instead of choice, but that would neither be useful, nor entirely true. Whatever the factors that go into the operation of my cognitive algorithms, they ultimately add up to me. Given this, I might still believe that I have free will… while at the same time knowing that the question itself does not have the meaning I thought it had before I seriously considered the question.
This is not a problem. A computer runs a program the same way in almost all future outcomes, weighed by probability. QM shows how to determine what happens even in cases where it’s not as simple as that.
Do neurons operate at the quantum level? I thought they were large enough to have full decoherance throughout the brain, and thus no quantum uncertainty, meaning we could predict this particular version of your brain perfectly if we could account for the state and linkages of every neuron.
Or do neurons leverage quantum coherence in their operation?
I was once involved in a research of single ion channels, and here is my best understanding of the role of QM in biology.
There are no entanglement effects whatsoever, due to extremely fast decoherence, however, there are pervasive quantum tunneling effects involved in every biochemical process. The latter is enough to preclude exact prediction.
Recall that it is impossible to predict when a particular radioactive atom will decay. Similarly, it is impossible to predict exactly when a particular ion channel molecule will switch its state from open to closed and vice versa, as this involves tunneling through a potential barrier. Given that virtually every process in neurons is based on ion channels opening and closing, this is more than enough.
To summarize, tunneling is as effective in creating quantum uncertainty as decoherence, so you don’t need decoherence to make precise modeling impossible.
Quantum uncertainty is decoherence. All decoherence is uncertainty. All uncertainty is decoherence. If it’s impossible to predict the exact time of tunneling, that means amplitude is going to multiple branches, which, when they entangle with a larger system, decohere.
That is not quite the conventional meaning of decoherence, though. Of course, if I recall from your QM sequence, it is, indeed, yours. Let me explain what I think the difference is between the two phenomena: a spin measurement and the tuneling process.
During an interaction such as spin measurement, a factorized state of a quantum system becomes entangled with the (quantum) state of the classical system as some of the terms in the product state decay away (according to Zurek, anyhow). The remaining “pointer” states correspond to what is usually termed “different worlds” in the MWI model. I believe that this is your interpretation of the model, as well.
Now, consider radioactive decay, or, to simplify it, a similar process: relaxation process of an excited atom to its ground state, resulting in an emission of a photon. This particular problem (spontaneous emission) requires QFT, since the number of particles is conserved in QM (though Albert Einstein was the first to analyze it). Specifically, the product state of an excited atom and the ground (vacuum) state of the electromagnetic field evolves into a ground state of the atom and an excited state of the field (well, one of almost infinitely many excited states of the field, the “almost” part being due to the Planck-scale cutoff). There is virtually no chance of the original state to reappear, as it occupies almost zero volume in the phase space (this phase space includes space, momentum, position, spin, etc.). I believe even time is a part of it.
To call radioactive decay “decoherence”, one would have to identify the ground state of the field (electromagnetic vacuum) with the classical system that “measures” the excited atom. Calling a vacuum state a classical system seems like a bit of a stretch.
An alternative approach is that the measurement happens when an emitted photon is actually detected by some (classical) external environment, or when the atom’s state is measured directly by some other means.
I am not sure if there is a way to distinguish between the two experimentally. For example, Anton Zeilinger showed that hot fullerene molecules self-interfere less than cold ones, due to the emission of “soft photons” (i.e. radiating heat). His explanation is that the emitted radiation causes decoherence of the fullerene molecule’s factorized state, due to the interaction with the (unspecified) environment, and hotter molecules emit shorter-wave radiation, thus constraining the molecule’s position (sorry, I cannot find the relevant citation).
If you identify each of the branches in the MWI model with each possible excited state of the electromagnetic field, you would have to assume that the worlds keep splitting away forever, as all possible (measured) emission times must happen somewhere. This is even more of a stretch than calling the vacuum state a classical system.
Feel free to correct me if I misunderstood your point of view.
Interesting! I hadn’t thought about quantum tunneling as a source of uncertainty (mainly because I don’t understand it very well—my understanding of QM is very tenuous).
You don’t need macroscopic quantum entanglement to get uncertainty. Local operations (chemical reactions, say) could depend on quantum events that happen differently on different branches of the outcome, leading to different thoughts in a brain, where there’s not enough redundancy to overcome them (for example, I’ll always conclude that 6*7=42, but I might give different estimates of population of Australia on different branches following the question). I’m not sure this actually happens, but I expect it does...
I’m not sure I understand how quantum events could have an appreciable effect on chemical reactions once decoherance has occurred. Could you point me somewhere with more information? It’s very possible I misunderstood a sequence, especially the QM sequence.
I could also see giving different estimates for the population of Australia for slightly different versions of your brain, but I would think you would give different estimates given the same neuron configuration and starting conditions extremely rarely (that is, run the test a thousand times on molecule for molecule identical brains and you might answer it differently once, and I feel like that is being extremely generous).
Honestly I would think the decoherance would be so huge by the time you got up to the size of individual cells that it would be very difficult to get any meaningful uncertainty. That is to say, quantum events might be generating a constant stream of alternate universe brains, but for every brain that is functionally different from yours there would be trillions and trillions of brains that are functionally identical.
If you include electrons a single water molecule has 64 quarks, and many of the proteins and lipids our cells are made of have thousands of atoms per molecule and therefore tens of thousands of quarks. I am having a hard time envisioning anything less than hundreds of quarks in a molecule doing enough to change the way that molecule would have hooked into its target receptor, and further that another of the same molecule wouldn’t have simply hooked into the receptor in its place and performed the identical function. There may be some slight differences in the way individual molecules work, but you would need hundreds to thousands of molecules doing something different to cause a single neuron to fire differently (and consequently millions of quarks), and I’m not sure a single neuron firing differently is necessarily enough for your estimate of Australia to change (though it would have a noticeable effect given enough time, a la the butterfly effect). The amount of decoherance here is just staggering.
To summarize what I’m saying, you’d need at least hundreds of quarks per molecule zigging instead of zagging in order for it to behave differently enough to have any meaningful effect and probably at least a few hundred molecules per neuron to alter when/how/if that neuron fires, or whether or not the next neuron’s dendrite receives the chemical signal. I would think such a scenario would be extremely rare, even with the 100 billion or so neurons and 100 trillion or so synapses in the brain.
You may be right, I don’t really know what’s involved in chemical reactions. A chemist knowing enough theory of a physicist would likely be able to reliably resolve this question. Maybe you really know the answer, but I don’t know enough to be able to evaluate what you wrote...
See my comment.