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colmmaccyesterday at 11:22 PM2 repliesview on HN

Lesser known but possibly more relevant to most HN readers are Feynman's lectures on computation - https://theswissbay.ch/pdf/Gentoomen%20Library/Extra/Richard... . There's some really great explanations in there of computability, information theory, entropy, thermodynamics, and more. Very little of it is now out-dated.


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Isamutoday at 2:32 AM

Apropos of Feynman on computing, the story of his time working at Thinking Machines Corp https://longnow.org/ideas/richard-feynman-and-the-connection...

“For our first seminar he invited John Hopfield, a friend of his from CalTech, to give us a talk on his scheme for building neural networks. In 1983, studying neural networks was about as fashionable as studying ESP, so some people considered John Hopfield a little bit crazy. Richard was certain he would fit right in at Thinking Machines Corporation.”

jesusloptoday at 1:46 AM

Interesting, he also talks about quantum computing (a first?): p. 191, "We now go on to consider how such a computer can also be built using the laws of quantum mechanics. We are going to write a Hamiltonian, for a system of interacting parts, which will behave in the same way as a large system in serving as a universal computer."

p. 196: "In general, in quantum mechanics, the outgoing state at time t is eⁱᴴᵗ Ψᵢₙ where Ψᵢₙ is the input state, for a system with Hamiltonian H. To try to find, for a given special time t, the Hamiltonian which will produce M = eⁱᴴᵗ when M is such a product of non-commuting matrices, from some simple property of the matrices themselves, appears to be very difficult.

We realize, however, that at any particular time, if we expand eⁱᴴᵗ out (as 1 + iHt − H²t²⁄2 + …) we'll find the operator H operating an innumerable arbitrary number of times — once, twice, three times, and so forth — and the total state is generated by a superposition of these possibilities. This suggests that we can solve this problem of the composition of these A’s in the following way..."

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