On Fri, Jun 21, 2019 at 8:13 PM Lawrence Crowell < [email protected]> wrote:
*> A Hadamard gate is not a unitary operation* I don't quite understand that. I thought all quantum logic gates could be represented by a symmetric Hermitian matrix, and if all the probabilities don't add up to exactly 1 it's hard to see how it could be of much use to physics. What does a probability of 110% mean? > *and so one can prepare or duplicate states that way.* If you could do that then you could get around the Heisenberg Uncertainty Principle. If you could make 2 copies you could measure the position of one particle to arbitrary precision and not worry about velocity, and then measure the velocity of the other copy to arbitrary precision and not worry about position. And they you'd know both position and velocity to arbitrary precision. It also seems to me that not being able to duplicate a quantum state is the only thing that prevents you from sending messages faster than light. Suppose Alice and Bob are many light years apart and have entangled electrons. Bob makes lots of clones of his electron and measures them, if they're all spin up then Bob instantly knows that Alice has measured her electron, if there is a 50 50 mix then Bob instantly knows that Alice has not measured her electron. Measuring could mean dot and not measuring could mean dash, and presto you've got a faster than light telegraph. I must therefore conclude that it's impossible for Bob to make lots of clones of his electron. > *> The computer of the year 2030 will have a network of processors. There > will continue to be a straight up von Neumann type processor, but what can > run in parallel with neural networks, quantum processors and other > specialized processors. The Ras-Tal theorem illustrates a reduction in the > need for oracle input.* I've never heard of the Ras-Tal theorem, I Googled it but all Google could find was your very post mentioning it, Bing couldn't even find that. John K Clark -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAJPayv1ejQ67-ro937DiLz%2BwUr8YNvxoN86M4RzGfidqb8UA-A%40mail.gmail.com.
