David P. DiVincenzo from the IBM Research Division has written an article in the 13th October issue of SCIENCE magazine (vol. 270, pg. 255-261) entitled "Quantum Computation". The article is nicely divide into subsections: - Building blocks of quantum logic - Quantum circuits - Peter Shor's prime factorization - The decoherence problem - Outlook
From the outlook section "It is evident from this survey of the current state of the art in quantum experimental physics that the construction of quantum computers is presently in the most rudimentary stage, and that to even think about a procedure like Shor factorization, which might require millions of operations on thousands of qubits, might be absurdly premature."
If that is the good news for Cypherpunks, then the great news is the following. ". . even a few bits of quantum computation will be very useful in performing so-called Bell measurements, which could be used to implement quantum teleportation, in which an unknown quantum state can be trasmitted to a remote location. At perhaps the 10-qubit level, a quantum computer becomes capable of performing Schumacher's quantum coding, which would be of interest in the implementation of efficient quantum cryptography. And at perhaps the 100-qubit level, a quantum computer becomes an efficient repeater for a noisy (that is partially decohered) quantum cryptographic link." It looks like the advantages of quantum computing accrue to Alice and Bob, long before it becomes useful to Eve and Mallet. A must read for aficianados of "alternative computing". Here are some URLs from the references http://vesta.physics.ucla.edu/~smolin/ (Quantum Information Page, Center for Advanced Accelerators) http://eve.physics.ox.ac.uk/QChome.html (Quantum Computation and Cryptography page, Clarendon Laboratory, Oxford University) C. J. Leonard ( / "DNA is groovy" \ / - Watson & Crick <cjl@welchlink.welch.jhu.edu> / \ <-- major groove ( \ Finger for public key \ ) Strong-arm for secret key / <-- minor groove Thumb-screws for pass-phrase / )