Re: Fermi "Paradox"

From: Anders Sandberg (asa@nada.kth.se)
Date: Wed Aug 06 2003 - 10:30:49 MDT

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    On Wed, Aug 06, 2003 at 08:16:26AM -0700, Charles Hixsn wrote:
    > If we had entanglement linkages built into M-brains, then there would be
    > no practical limit (foreseeable from here) to the degree of
    > intelligence. Actually, a lot of things would depend on the exact
    > nature of the link. If it had a long start-up delay, or was expensive
    > to use (say, emitted a lot of heat, or had a slow bit rate), then there
    > could well still be speed limits in how fast the final
    > M-brain-with-quantum-link could think, but I can't see any limit on the
    > size of problem that it could solve. Merely on the speed at which it
    > could be solved. I suppose that one could say that the same is, in
    > principle, true of even a simple Turing machine, but this isn't the same
    > kind of limit. The separable parts could be handled separately...

    Huh? I get the feeling that you think entanglement links are some
    kind of communications channels you can send information through?
    Entangled particle pairs do have shared quantum information, but
    you cannot get classical information from that. So if module A is
    entangled with module B, you could get perfectly correlated random
    numbers, but not send the contents of A to B over the link.

    Entanglement in itself does not consume any energy, but you still
    have to send the carrier particle from the origin to the
    destination to get the link (and once you have used up the
    entanglement you need another). It is not FTL communication.

    > If the link were somewhat expensive, but had a fast bit-rate, then
    > M-Brain modules would get, say, as large as a desk, or perhaps a shoebox
    > and these modules would be linked using some development from, perhaps,
    > Beowulf technology (or Globus?). Thus each M-Brain module would have
    > perhaps 1000 times the computing capacity of a human brain (or more, I'm
    > being a bit conservative here) and these modules would be linked
    > "instantaneously" to a net which could be spatially distributed
    > throughout the universe.

    Yes, but this is based on FTL communication, not entanglement. If
    we can make small wormholes this might work.

    > Simply having the possibility of a quantuum linkage doesn't tell one
    > enough about the engineering trade-offs. And since we don't yet know
    > how to do it, we don't know what the constraints and limitations would
    > be.

    Hmm? Entanglement is relatively well understood (at least we think
    we understand it, no anomalies that I know of). I get the feeling
    you have not kept up with the field of quantum cryptography, which
    is where most of the action is right now. The latest issue of
    Science has a good article about it.

    Science, Vol. 301, Issue 5633, 621-623, August 1, 2003
     
    Long-Distance Free-Space Distribution of Quantum Entanglement

    Markus Aspelmeyer,* Hannes R. Böhm, Tsewang Gyatso, Thomas
    Jennewein, Rainer Kaltenbaek, Michael Lindenthal, Gabriel
    Molina-Terriza, Andreas Poppe, Kevin Resch, Michael Taraba, Rupert
    Ursin, Philip Walther, Anton Zeilinger

    We demonstrate the distribution of quantum entanglement via optical
    free-space links to independent receivers separated by 600 m, with
    no line of sight between each other. A Bell inequality between
    those receivers is violated by more than four standard deviations,
    confirming the quality of the entanglement. This outdoor experiment
    represents a step toward satellite-based distributed quantum
    entanglement.

    -- 
    -----------------------------------------------------------------------
    Anders Sandberg                                      Towards Ascension!
    asa@nada.kth.se                            http://www.nada.kth.se/~asa/
    GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y
    


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