Hvis man vælger at benytte superpositionen i kvanteberegningerne, kan en eksponentiel algoritme hastighedsforøgelse fås, hvis man kan finde ud af at lave en sådan algoritme. Det bemærkelsesværdige er, at denne hastighedsforøgelse fås med eksponentiel mindre brugt energi, i forhold til en klassisk algoritme på en traditionel [[supercomputer]]!<ref name="Brassard2003">[https://arxiv.org/pdf/quant-ph/0306182.pdf 25 June 2003, arxiv.org, Eli Biham, Gilles Brassard, Dan Kenigsberg and Tal Mor: Quantum Computing Without Entanglement] Citat: "...It is generally believed that entanglement is essential for quantum computing. We present here a few simple examples in which quantum computing without entanglement is better than anything classically achievable, in terms of the reliability of the outcome after a fixed number of oracle calls...When information is lacking about the state of a qubit, we say that this qubit is in a mixed state...A quantum mixed state ρ of several qubits is called a product state if it can be written as a tensor product of the states of the individual qubits...Quantum computers can manipulate quantum information by means of unitary transformations [11, 14, 7]. In particular, they can work with superpositions...The linearity of quantum mechanics gives rise to two important phenomena. (1) Quantum parallelism: we can compute f on arbitrarily many classical inputs by a single application of Uf to a suitable superposition...On the other hand, it has been demonstrated that quantum computers can solve some problems exponentially faster than any classical computer provided the input is given as an oracle[8, 2], and even if we allow bounded errors [18]...A fundamental question is: Where does the surprising computational advantage provided by quantum mechanics come from? What is the nonclassical property of quantum mechanics that leads to such an advantage? Do superposition and interference provide the quantum advantage? Probably the most often heard answer is that the power of quantum computing comes from the '''use of entanglement''', and indeed there are very strong arguments in favour of this belief. (See [12, 4, 13, 10, 15] for a discussion.) We show in this paper that this common belief is '''wrong'''..."</ref><ref name="Milestone"/>
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