Most experts seem to think that whole brain emulation will not require emulation down to the quantum level, but perhaps at the level of atoms or even molecules, either of which is far more computationally tractable than quantum-level brain emulation. Those who think quantum-level emulation will be required for whole brain emulation are often considered to be cranks.
However, it is worth noting that a few biological processes - including photosynthesis - have recently been found [excellent video lecture] to depend on the particularities of quantum phenomena. This lends no support to Penrose's views on quantum phenomena and the brain, but it may not be so crankish after all to suppose that whole brain emulation may require emulation down to the quantum level.
Thoughts?
Links:
On photosynthesis, see Fleming's papers on the topic.
Here is the quantum bird navigation paper.
Here is some coverage on Turin's controversial theory of quantum smell.
The problem of emulating human "minds" might be much more difficult than just emulating the human brain. Here are three quotes that will highlight why this might be the case:
Philosophy in the Flesh, by George Lakoff and Mark Johnson
What a maze-solving oil drop tells us of intelligence (Original)
Evolution of Language Takes Unexpected Turn (See also, Is Grammar More Cultural Than Universal? Study Challenges Chomsky’s Theory)
Even more: Embodied cognition
I don't know what to make of this as I haven't done any research into it but I thought it should be accounted for when one wants to talk about the emulation of "minds". It seems a lot of what makes us human, intelligent and what shapes our languages, values and goals seems to be a complex interrelationship between our brain, body, culture and the environment.
Most of the quotes above (at least, the ones that make sense) are talking about the way that intelligence grows in the first place, not about what would happen if you changed the context for a grown adult brain. Since a person paralyzed in an accident or stroke can nevertheless keep their mental faculties, it seems that changing the connection between the brain and its body/environment need not destroy the intellect that's already formed.
Also, it would be pretty reasonable to simulate some kind of body and environment (in less detail than one simulates the brain) while you're at it. Would that address your query?