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It's not misleading: Quantum computers ARE computers. (Or WILL BE when we build proper ones...) David Deutsch formalized universal quantum computers -in analo

It's not misleading: Quantum computers ARE computers. (Or WILL BE when we build proper ones...) David Deutsch formalized universal quantum computers -in analogy to a universal classical computers in the 80s. The starting point is basically noticing the mismatch between the classical theories of computing and quantum physics. From the abstract of 'Quantum theory, the Church-Turing principle and the universal quantum computer': >It is argued that underlying the Church-Turing hypothesis there is an implicit physical assertion. Here, this assertion is presented explicitly as a physical principle: ‘every finitely realizable physical system can be perfectly simulated by a universal model computing machine operating by finite means’. Classical physics and the universal Turing machine, because the former is continuous and the latter discrete, do not obey the principle, at least in the strong form above. A class of model computing machines that is the quantum generalization of the class of Turing machines is described, and it is shown that quantum theory and the ‘universal quantum computer’ are compatible with the principle. Computing machines resembling the universal quantum computer could, in principle, be built and would have many remarkable properties not reproducible by any Turing machine. These do not include the computation of non-recursive functions, but they do include ‘quantum parallelism’, a method by which certain probabilistic tasks can be performed faster by a universal quantum computer than by any classical restriction of it.

hnfong 3y ago
The abstract seems to make the concept more profound than it actually is... and I daresay is prone to confuse the uninitiated. For one I don't think there's understood to be an implicit physical principle in Church-Turing thesis. The core idea of the thesis is that human thought can be modeled by a Turing-complete machine. It is silly to say that the thesis implies an assertion that the classical(non-quantum) physical system popular at the time, now known to be flawed (and possibly inconsistent), could be simulated by a Turing-complete machine. What I'm trying to say is, if the best known physical system known by science could be wrong or flawed or inconsistent (and it always has been, we haven't cracked all the secrets of the physical universe yet), it seems silly to assert that some computing system could perfectly simulate it. IMHO those ideas would be relevant only if there is evidence that human thought is capable of performing computation that cannot be simulated by a classical Turing machine because the human mind uses some features of the physical universe that the machine did not use. But on that front, AFAIK, classical computers can simulate quantum computers albeit with an exponential slowdown.

hnfong 3y ago

The abstract seems to make the concept more profound than it actually is... and I daresay is prone to confuse the uninitiated. For one I don't think there's understood to be an implicit physical principle in Church-Turing thesis. The core idea of the thesis is that human thought can be modeled by a Turing-complete machine. It is silly to say that the thesis implies an assertion that the classical(non-quantum) physical system popular at the time, now known to be flawed (and possibly inconsistent), could be simulated by a Turing-complete machine. What I'm trying to say is, if the best known physical system known by science could be wrong or flawed or inconsistent (and it always has been, we haven't cracked all the secrets of the physical universe yet), it seems silly to assert that some computing system could perfectly simulate it. IMHO those ideas would be relevant only if there is evidence that human thought is capable of performing computation that cannot be simulated by a classical Turing machine because the human mind uses some features of the physical universe that the machine did not use. But on that front, AFAIK, classical computers can simulate quantum computers albeit with an exponential slowdown.