From: Charles Hixsn (charleshixsn@earthlink.net)
Date: Wed Aug 06 2003 - 11:28:31 MDT
Anders Sandberg wrote:
>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
>>...
>>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?
>
>
I believed that was the proposition. I find it dubious, but
conceivable. If you were discussing using them as q-bits, ... well, I
don't really know how to think about that. I REALLY don't. If that is
ever made easy, it could be much more dramatic than thinking of them as
communication links. The estimates that I've seen as to how capable
they would be make me rank them as "Don't try to think past this until
engineering contraints are more obvious." 32-qbits would be, O, 32
atoms (plus, of course, a whole lot of support equipment,
refridgerators, etc.). And large classes of problems would disolve into
"trivially solved". Large classes. And this change could come *quickly*.
>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.
>
>
I understand that this is current belief, and I accept it as the most
probable truth. Certainly there will be stringent limits on and
deviations from this assessment. But I've seen many "well accepted"
theories reinterpreted. And so I'm unwilling to consider this a "final
word". (Big crunch, expand gently forever, or tear yourself to
ribbons? What's the fate of the universe. Just two years ago it was
"certain" that the universe would either collapse violently, or expand
forever at a decreasing rate. But now there's doubt.)
>>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.
>
>
>
How does one get the negative energy density to stabilize them? This is
another possibility, but I feel realtively confident that wormhole
communicaitons will always be expensive. But it might have a very fast
bit rate. (Would a high speed laser link cause problems with keeping up
the needed negative engery gradient? I don't know the rules here.)
>>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.
>
>
Many people understand a lot more about it than I do. I'm basically a
programmer. And, I must admit, cryptography doesn't interest me. My
understanding is more at the level of Scientific American and Science
News. So I know the general outlines of current beliefs on, say,
entanglement, but not the details or the certainty. I do, however,
remember the absolute confidence that I heard given to sentences like
"We'll never be able to see a single atom. Quantuum theory forbids
it." Which is sort of true...but not really, as quantuum dots and the
Scanning Electron Microscope showed. The math was solid, but the
translation into physical models was flawed.
>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.
>
I haven't read the article, but I'm aware of it. And I know that what
they demonstrated was the transportation of infomation via ordinary
particles. (Perhaps photons? I expect so, but I didn't read the
article.) This doesn't, in and of itself, imply anything about other
approaches. So I'm still willing to consider that they might exist.
I'm sorry that I misunderstood what you were proposing. (Which I'm
still not certain about. Qbits is all I could think of after your
response...and that didn't come to mind immediately.)
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