Depends how you define upload. Why couldn't a computer just simulate a persons outputs based on recordings of their life. Does virtualization of life really need to have consistent consciousness? Maybe rip would be a better word than upload.
You can't extract all the information contained in a brain non-destructively. You'd need reproduce the neural graph, 10ˆ11 neurons with an average of 7000 synapses (connections), along with the type of neurons, the dendritic trees, the strength of the synapses, the map of active genes in each cell, and most probably other cellular parameters, like the state of the cytoskeletton. Probably even more.
It would require something along the lines of the Allen Brain Atlas Project [0], but much more advanced, since you'd have to extract all the information out of one brain. The Allen project has several atlasses, built out of different brains. They've yet to map the circuitry of a mouse brain (the project was started in 2011).
Even if it were possible to extract the relevant info, since the extraction would destroy the brain, you'd better have a conscious clone, which preserves the identity of the original. What happens to one's identity is also troubling, since you could, theoretically, instantiate several copies of someone. I'm not sure the identity would be carried over, actually.
By identity, I mean the fact that you're the same person in the morning that you were when you fell asleep. Your consciousness dissolves and re-emerges, and you're still yourself. We take it as granted, but it is extremely puzzling to me.
Another problem is that the relations between time and consciousness have yet to be understood. The fact that the brain processes information in parallel is probably important, meaning that a fast serial simulation by turing machines would not necessarily cut it, even with "massive" supercomputers. The level of parallelism in the brain will not be achieved in a long time in silico, at least not with the current approach.
Hmm, on your last point, assuming the serial computation is done by calculating brain state for each time slice, would this end up being functionally equivalent (if slower) than the parallel brain process? Since from the "brain's" perspective, everything is getting updated in parallel?
"To be" assumes that 1) it is possible to extract the information non-destructively, and 2) that it is possible to extract the information at all. The closer the measurement, the more you measure the interaction between the measuring instrument and the observed phenomenon, rather than the phenomenon itself.
Regarding the Ship of Theseus, our identity is most likely tied to an ever evolving process that depends on the architecture of our brains rather than a fixed set of molecular components. Beside the neuronal DNA, most if not all cell components are subject to a turnover.
That wouldn't work because it would include things a person did at various times during their life. It also would be hard to make sure that it reacts or changes in response to new stimuli in the same way that person would.
A copy is never good enough. I think the best approach would be to enhance the brain by attaching devices to it directly. This maintains continuity and doesn't raise as many philosophical questions. This also raises other interesting questions like how long can the brain live in a suspended solution and where would all these consciousnesses live...
Slowly replace organics with mechanics until you only have a machine left. If you keep it gradual, you never know when you stop being a cyborg and start being a full fledged android.
You might not be able to make a perfect quantum copy, but with iterative refinement you can get arbitrarily close. I think 99.9999999% or so would be good enough.
You might be interested in Greg Egan's [0] story 'The Jewel' [1]. [edit] To clarify, it's actually two stories "Learning to Be Me" and "Closer".
Greg Egan is one of my favourite modern sci-fi writers. He explores interesting and hard ideas about what it means to be human by placing humanity in thought provoking situations.
In 'The Jewel' we have developed an implant that learns how to 'be' the host. At some point your brain is removed and the jewel takes over your functioning. The thing is, what happens when something goes wrong... boom boom booooom!!?!?!
