TheVat

Hello. Background in life sciences, but have ranged widely into other areas including AI, cognitive science, astronomy, and cosmology. Also some interest in bioethics and philosophy of science. I was, until a month ago, the Admin of sciencechatforum.com, a website that crashed after it was bought up by a "web development" company that turned out to be running a Ponzi Scheme on its investors and was seized by the U.S. SEC. The receivership handling the liquidation of its assets could not, for reasons obscure to me, keep the website up and running. One day, we all woke up and the site was gone. ScienceForums seems to be a website with a rather similar structure and a pretty good signal/noise ratio, which suggests good moderation and tossing of trolls. Well done. This refugee from late-stage capitalism is happy to be here!

Hello. Some speculate that a quantum mechanical system which somehow uses an infinite superposition of states could compute a noncomputable function. This is not possible using the standard QUBIT machine, because it is proven that a regular quantum computer is PSPACE-reducible (a quantum computer running in polynomial time can be simulated by a classical computer running in polynomial space). What is potentially non-deterministic is extracting the output of a computation in classical terms. The same final quantum state may be measured as different classical states with varying probabilities. However, if you choose your computation such that the final state is an eigenstate of whatever value you intend to measure, such that the probability of one particular classical output is 1 and all others are 0, then it is effectively deterministic. This is not always possible or practical to do, in which case you may need to to run the quantum algorithm many times to extract the effective classical probability distribution, but effective quantum computation depends on structuring your algorithm to boost the amplitude of the intended output as much as possible, while getting all of the wrong answers to destructively interfere, such that you don’t have to re-run your quantum computation an impractically large number of times. I guess there are nondeterministic models (as noted above), which are just that, models of a hypothetical device sometimes called a hypercomputer. But in the RW, computations are deterministic.