Wicked. I was just thinking about writing a script to scrape 'em and stick 'em on my phone for those tube journeys when I haven't got a book with me.

Been using the Harry Potter fan-fic for that but seem to be about to run out of it.

Thanks to all those who have already done it for me :)

If the topic is the technical plausibility of cryonics then this is on-topic, but I'm hoping to focus a little more narrowly than that, on the specific subject of existing writing that argues against cryonics, its accuracy and quality, and what we can infer from that.

BTW: I too am in the UK and having real trouble!

If the topic is the technical plausibility of cryonics then this is on-topic, but I'm hoping to focus a little more narrowly than that, on the specific subject of existing writing that argues against cryonics, its accuracy and quality, and what we can infer from that.

BTW: I too am in the UK and having real trouble!

I'm a long way from being an expert neuroscientist, but as far as I can tell the mechanism under which neural change happens essentially involves a few physical changes:

1) Myelination - the Myelin coating over the Axon of a neuron grows, making the Axon conduct it's signal more powerfully and quickly

2) Change in number and distribution of neurotransmitter receptors in the dendrites of the neuron. Obviously the more of them you have, the more likely the neuron is to fire in the presence of the transmitter which fits that receptor.

3) Change in the number and distribution of vesicles which release neurotransmitters in the Axon Terminal. When the neuron fires, the vesticles in it's Axon terminal's release their load of neurotransmitters. Again, the more of them you have the stronger the signal to make the neuron the other side of the synapse fire.

4) The actual path the Axon's and Dentrites take, snaking from one cell to the next. Litterally the 'wiring'.

There may well be other changes to the neural structure which change the way it behaves, but these seem to be the major mechanisms. Interestingly, a neuron firing tends not only to release neurotrasmitters from it's vesticles, but also to change the structure of the neuron, make it grow more receptors etc

So does Cryonics actually preserve these things?

I'm not in a position to tell. If the cell walls were really being burst, then no, I doubt that the number and distribution of vesticles and receptors would be preserved since those things are built into the cell walls. My impression was that proper cryopreservation did indeed store the cells intact though.

If the cells are stored intact, including the position of the receptors and releasors in the cell walls at each end of every branch of the axons in the neurons, then I think this seems likely to be where the brain's long-term state is stored.

There'll doubtless also be short-term memories which are just feedback loops of signals travelling around the brain. They'll be lost, I would think, just as they were lost in my brother when he spent a few weeks in a coma and remembered nothing until the day before he got beaten up.

Course, I'm nowhere near qualified to really judge either. All I've done is read a bit.

I signed up for the Alcor UK mail-list at the beginning of the year. It's pretty much silent though. As far as I can tell, shipping your dead body to the US is the only way it's really gonna work. I fear that makes it much less viable here than there.

Thanks folks, sounds like the entire point of quantum computing is to avoid the kinda differences in interpretation that Copenhagen/MWI are concerned with, so my suspicion that a MW computational image would help is mistaken. Which is good, read around some Quantum Algorithms a bit. Have a better grasp of how that actually works than the terrible "explore all possibilities and pick the best" line that seems to come up so much.

Still leaves me a bit at a loss with these quantum effects in photosynthesis though:

We have obtained the first direct evidence that remarkably long-lived wavelike electronic quantum coherence plays an important part in energy transfer processes during photosynthesis,” said Graham Fleming, the principal investigator for the study. “This wavelike characteristic can explain the extreme efficiency of the energy transfer because it enables the system to simultaneously sample all the potential energy pathways and choose the most efficient one.”

Seems likely that line about "simultaneously sampling all the potential energy pathways and choosing the most efficient one" is just as misleading as the similar line in explaining how to quantumly factor a number.

Humm. Oh well. Can't expect to clear up all my confusion in one day. It's Friday Night, I should go find something fun to do.

Yes, I think that's a good explanation. One question it raises is ambiguity in thinking of QM via "many worlds". What constitutes a "world"? If we put a system into a coherent superposition, does that mean there are two worlds? Then if we transform it back into a pure state, has a world gone away? What about the fact that whether it is pure or in a superposition depends arbitrarily on the chosen basis? A pure-state vertically polarized photon is in a superposition of states using the diagonal basis. How many worlds are there, two or one? This interpretation can't be more than very metaphorical - it is "as though" there are two worlds in some sense.

Or do we only count a "world" when we have (some minimal degree of) decoherence leading to permanent separation? That way worlds never merge.

The explanation of QC in terms of MWI will vary depending on which interpretation we use. In the second one (worlds on decoherence) the explanation is pretty much the same as in any other interpretation. We put a system into a coherent state, manipulate it into a pure state, and the measurement doesn't do anything as far as world splitting.

But in the first interpretation, we want to say that there are many different worlds, once for each possible value in the quantum registers. Then we change the amplitude of these worlds, essentially making some of them go away so that there is only one left by the time we do the measurement. It's an odd way to think of worlds.

Voted down for being off-topic. Feel free to delve into a deep discussion about the merits of doing this and what should be considered off-topic. Meanwhile, I'll say what I have to say anyway. Feel free to delve into a deep discussion about the merits of doing this as well.

The thing is, quantum mechanics looks like the Copenhagen interpretation. That's why Copenhagen hasn't been falsified. We've barely managed to produce any evidence against it. (I'm not considering its low-ish prior probability to be evidence, of course.) Therefore, if you want to explain an observed phenomenon, it's perfectly valid to explain it in terms of wavefunction collapse.

Note to self: ponder, and write something about, when it makes sense to explain something in terms of a mechanism you don't know exists.

Saying that a quantum algorithm is "simultaneously sampling all possibilities and choosing the best one" has always been, I've found, a strange way of putting it, since it suggests that quantum computing can do a lot more than it actually can. (Quantum superintelligence: simultaneously sample every possible process of reasoning and choose the most interesting one. Unfortunately, you can't actually do that.)

A quantum algorithm such as Grover's algorithm simply works by changing the probability amplitudes (i.e. the heights of the wavefunctions, the things that can interfere constructively and destructively, the things that determine the probability of each outcome) in such a way that the probability of the desired answer is much higher than the probability of any other answer. ("Probability" here is just a specific function of probability amplitude, which happens to be consistent with both quantum evolution and the laws of probability.) When you perform the observation, then, the majority of Bornstuff goes to the world where the answer observed is the desired one.

How does Grover's algorithm work, specifically? Well, there's a plane where one line is the algorithm's starting point, and another line is the correct answer; it uses reflections to rotate the point for a certain amount of time, until it's very close to the correct answer. I dunno. For details, see Wikipedia.

I recommend some reading: http://en.wikipedia.org/wiki/Quantum_computer Start with this and then if you want more detail look at: http://arxiv.org/pdf/quant-ph/9812037v1 The math isn't to difficult if you are familiar with math involved in QM, things like vectors, and matrices etc. http://www.fxpal.com/publications/FXPAL-PR-07-396.pdf This paper I skimmed it seems worth a read.

As to the author of the post to whom your responding what is your level of knowledge of quantum computing and quantum mechanics? By this I mean is your reading on the topic confined to Scientific American and what Eliezer has written or have you read for example Bohm on Quantum Theory?

My own problem with the torture versus dust specks problem is that I'm not sure dust specks are bad at all. I don't remember ever being irritated by a dust speck. Actually as I've started thinking about this I've been slightly irritated by several, but they've never before registered in my consciousness (and therefore aren't bad).