AranyKéz#113
Nem úgy van az ám, hogy minden nehéz problémára megadja a legpontosabb választ, azért ennek is van határa.
<< Upon termination of the algorithm, the 8-dimensional complex vector stored in the register must be somehow read off from the qubit register by a quantum measurement. However, by the laws of quantum mechanics, that measurement will yield a random 3 bit string (and it will destroy the stored state as well). This random string can be used in computing the value of a function because (by design) the probability distribution of the measured output bitstring is skewed in favor of the correct value of the function. By repeated runs of the quantum computer and measurement of the output, the correct value can be determined, to a high probability, by majority polling of the outputs. In brief, quantum computations are probabilistic >>
<< * One cannot measure the phase of ψ at any computational basis state so there is no way of reading out the complete answer. This is in the nature of measurement in quantum mechanics.
* There is no way to efficiently prepare the input state ψ. >>
Meg minél több qubit-tel dolgozik a gép, annál nagyobb probléma a dekoherencia.
Szóval a kvantumszámítógép se valami mágikus jótevő, a "lélek", meg egyebek létezéséről meg aztán főleg nem kéne következtetéseket levonni belőle.