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Quantum computers (assuming we can build one) can access computational resources far beyond what classical computers can do: imagine a classical computer so big
by mathgenius 9y ago
Quantum computers (assuming we can build one) can access computational resources far beyond what classical computers can do: imagine a classical computer so big and hot that it collapses down into a black-hole. Or it takes so long to run the computation (eg. a classical computer the size of the solar system) that heat-death of the entire universe comes first. These are the physical limitations of classical computation, and a quantum computer will (if we can build one) surpass this.
- klmr 9y ago> These are the physical limitations of classical computation Classical computation (i.e. the Turing machine) is a mathematical model, and isn’t bound by the physical limitations you imagine. In particular, a Turing machine (which, after all, requires an infinite tape) is already not physically possible.
- mathgenius 9y agoFrom the OP: "computations which current computers cannot replicate." I was just explaining a bit more why this is so. If it matters at all, I've just finished a PhD in quantum computing.
- h2j24 9y agoI don't think that's really true. The difference between a quantum computer and a classical computer is that a classical computer can represent N states given N bits, whereas a quantum computer can represent 2^N states given N q-bits. However, this has a major caveat: you can never know the state of the system. You only get to measure one value at a time and you can never re-create or copy a previously obtained state. Still, some clever people have figured out how to exploit this to achieve polynomial speedup on problems where certain properties of the problem are exploited to get around the limitation of measurement in a quantum system.