Periodically, Ray Kurzweil (author, inventor and machine intelligence pioneer) will pen an article or book making bold predictions about the future.  Recently Wired carried an article with quotes from him that suggested we will have reverse engineered the brain by 2030.

Kurzweil’s claims had biologists slapping their foreheads in irritation.  This post is not about Kurzweil.  It is about the biologists slapping their foreheads, or at least about some of the tangents the threads on their blogs took

Over at Pharyngula a discussion started up about the implications if we could create exact copies of ourselves.  Quantum mechanics has something to say about these speculations and maybe about how our brains work.

Could you ever make an exact copy of yourself?

The spanner in the works for this discussion is the Heisenberg uncertainty principle.  The uncertainty principle states that particular pairs of physical properties cannot both be known precisely.  The most famous example is also the one that would trip up anyone trying to make an exact replica of themselves.

The position and momentum of a particle cannot both be known precisely.  This uncertainty would introduce some small errors in our copy and mean no copy could be exactly identical to the original.

Does it matter?

When I walk into the Apple store, the iPads in there will all slightly different from one another thanks to random differences in their manufacture.  Nevertheless this doesn’t stop them being similar enough to all run the same software as each other.

Although a hypothetical copy of myself would have small differences introduced due to the uncertainty principle would this prevent it from running the “software” that makes me me?  This largely depends on whether the brain relies on quantum effects to work.  If so small changes might end up being significant.

Are our brains quantum computers?

Quantum effects are generally important at small scales.  The structures in our brains seem to be large enough that we can ignore quantum effects.

This view is not universal.  mathematician Roger Penrose has argued that the actions of our brains are fundamentally different to regular computers.  He proposes our brains must be some kind of quantum computers.  Moreover since the structures in our brains don’t seem to be small enough for this to be the case Penrose suggests this means we need a new and better theory of Quantum Mechanics!

Quantum brains (for quantum zombies)

I find this argument unconvincing.  If Quantum Mechanics is important at larger length scales why have our experiments not shown this?

Moreover all the “quantum programs” that have so far been proposed if we manage to build a quantum computer don’t do anything different to a regular computer.  They are just more efficient at the jobs they do (such as breaking the RSA cipher).  Therefore if our brains are doing things that a regular computer can’t do, it would seem Quantum Mechanics can’t explain this either.

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