... cracked!1
The reason is that in 1994 Peter Shor published a quantum algorithm which can factorize big numbers and solve the ``discrete logarithm'' in an efficient way (i.e., with polynomial complexity). Although a quantum algorithm which cracks a symmetric key efficiently has not been invented to date (at least to my knowledge), I suppose that it will be a question of a few years until one appears.
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... question.2
Perhaps in future times we will have inherently quantum-mechanical questions, or only need quantum information as answers. But this results in a whole new class of problems and goes beyond this project.
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... had.3
However, already in 1961 Rolf Landauer [2] from IBM has shown that any classical computation can equivalently be implemented in a reversible manner. Therefore, quantum logic in fact is a proper generalization of Boolean logic.
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