Quantum computers use various forms of quantum-level processs as an explicit part of their hardware. They make extensive use of {[qubits}} physcial elements that are in multiple superimposed states, sort of 0 and 1 at the same time. Quantum effects mean that effectively the same pieces of phsyical hardware simulrtaneosly perofrm multiple veesions of the same calculations, in contrats to classicla parallel processing where several physically dstinct processors do work on parts or variants of an algorith at the same time. Ths may be used ot modle quantum-level effects in phsyics, but can also be used in other kinds of algoriths. In particular many of the techniques used in cryptography will become insecure as a quantum computer can effectively try billions of options of a key similtaneously. In AI, one can imagie that certain kinds of neural network could benefit and one of the technologies for reservoir computing is quantum; however practical applications are probably still some years off Note that conventional computers may experience quantum effects such as tunneling between adjacent tracks, but this is usually regarded as a problem (indeed is one of the limits of convetional electronics), whereas quantum computers make deliberate use of these kinds of effect.
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