Sherry Mayo writes
Regarding the quantum cryptography thread: Some people expressed the view that although the idea may be workable, the manufacturing technology was a long way of being able to produce quantum computers. The quantum dot design proposed by Eckert et al for a quantum "factorisation engine" requires 100000 quantum dots (to factorise RSA-129 or similar) which are each about 10nm across to be fairly densly packed onto a chip. I'm not so sure about this being 'a long way off' in terms of materials technology,
Current art is fairly close to making components whose interaction requires a full quantum description. To make a quantum computer from such components requires that that the components be orders of magnitude faster and more reversible. Presently known quantum algorithms cannot tolerate the loss of a single quantum of energy, as this will introduce vacuum noise into the data. The longer the algorithm takes, the less energy there is in a single quantum of energy, thus the components for any long quantum algorithm, such as factoring a 1024 bit number, must be very fast indeed (near infrared frequencies) and extraordinarily efficient (fully reversible classical, non quantum computation.) Although quantum computers are interesting and important, they have no immediate practical relevance to cryptography. Error tolerant algorithms could change the picture substantially, but they would still require components far beyond current art. -- --------------------------------------------------------------------- We have the right to defend ourselves and our property, because of the kind of animals that we James A. Donald are. True law derives from this right, not from the arbitrary power of the omnipotent state. jamesd@netcom.com