Shor's Algorithms: Mad, Bad and Dangerous

[John Young <jya@pipeline.com>]

>From a WSJ nook review today of "The Fabirc of Reality,"
by David Deutsch (Allan lane, 390 pp., $29.95):

  Using something called "Shor's algorithm," a quantum
  computer can factor giant numbers and thereby break
  secret codes that no conventional computer could touch.

  The only way it could do this, Mr Deutsch argues, is by
  distributing its operations over many parallel universes.
  "To those who cling to a single-universe world-view,"
  he writes with evident asperity," I issue the challenge:
  *explain how Shor's algorithms works.*"

  Combining the many-universes notion with quantum probablity,
  and adding elements of Darwinism and Karl Popper's theory
  of knowledge, Mr. Deutsch apsires to nothing less than a
  complete understanding of "the fabric of reality." Arrogant
  in tone and marred by leaps of logic, his book nonetheless
  bristles with subversive insights about virutal reality,
  time travel, mathematical certainty and free will. 
  Intellectually speaking, Mr. Deutsch is mad, bad and 
  dangerous to know.