Number 281 - October 2006

Programming the Universe
This is the title of new book by MIT Professor Seth Lloyd. It was brought to my attention by Linda Gonse, editor/webmaster of the Orange County IBM PC Users Group (www.orcopug.org).    Professor Lloyd was the first to construct a primitive, but working quantum computer. These are based on the unusual behavior of elementary particles, such as electrons, according to the rules of quantum mechanics. Because such particles can exist simultaneously in a number of different states, they can conceptually be used in computers to replace the usual binary (0 or1) digital bits with quantum bits, dubbed qubits, that can assume many values between 0 and 1 at the same time. If you want more detail, read the book or any of many books written about quantum mechanics for the the uninitiated.    The trouble with using qubits is that they only exhibit that strange behavior when no one is watching them. Like unruly schoolchildren, they all look sweet and innocent as soon as the teacher turns around from the blackboard. Hence the difficulty of actually building a quantum computer, but the rewards are enormous. Even with a relatively small number of qubits a quantum computer can solve problems that current digital computers can never hope to handle. Quantum computers will be able to calculate reliable weather forecasts and, by being able to factor even the largest prime numbers in a short time, thwart the security currently provided by encryption systems.	Since the universe is full of elementary particles, it has been suggested by several scientists that it is like a quantum computer, constantly computing what will happen next. Lloyd provides a "thought experiment" in which we have a quantum computer simulating the whole universe. The output from such a computer would be indistinguishable from the universe itself, he states, concluding that the universe is therefore itself a computer, and hence the title of the book. I must confess to some skepticism. The computer, being part of the universe, must simulate itself, but that simulation also must simulate itself--you see where that is going: like standing between mirrors. Anyhow, if anyone ever tries to build such a monster, I hope they don't use tax money. Can you imagine the electric bill? And you can't even turn it off overnight!    Programming the Universe by Seth Lloyd is published by Alfred E. Knopf, 2006. I like the way it explains the strange behavior of quantum objects in understandable language. Another part of the book explains the connection between entropy and information theory. The Evansville Public Library has 5 copies on the shelves at its branches, in case you don't want to spend $25.95 (list) to buy it.    posted by SW Indiana PC Users Group, Inc at http://swipcug.blogspot.com/2006/05/programming-universe.html" title="permanent link
Number 281 - October 2006