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How efficiently can a computer transform physical energy into mathematical work? Can we create a computer that would solve mathematical problems too complex to be solved by all of the computers in the world today even if they number-crunched for millions of years? And how can we send information over a network and be sure no one eavesdrops on our transmission?
Dr. Charles H. Bennett, an expert in the physics of information, is helping to answer these questions. Some of the answers involve treating information not as definite thing whose value is independent of the act of observing it, but, rather, as a more slippery, shadowy thing that, like an atom or electron, is disturbed by the act of observing it.
Shortly after he came to IBM in 1973, Bennett found a surprising answer to the first question, which had been raised by another IBM physicist, Rolf Landauer. The surprising answer was that computers are not like steam engines. A steam engine, no matter how carefully built, requires a certain amount of fuel to do a given amount of work. But, Bennett found, there is no limit in principle to the amount of mathematical work a computer can do on a given amount of electricity.
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