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arXiv · 1401.8127

Computational advantage from quantum-controlled ordering of gates

Mateus Araújo·Fabio Costa·Časlav Brukner
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Abstract

It is usually assumed that a quantum computation is performed by applying gates in a specific order. One can relax this assumption by allowing a control quantum system to switch the order in which the gates are applied. This provides a more general kind of quantum computing, that allows transformations on blackbox quantum gates that are impossible in a circuit with fixed order. Here we show that this model of quantum computing is physically realizable, by proposing an interferometric setup that can implement such a quantum control of the order between the gates. We show that this new resource provides a reduction in computational complexity: we propose a problem that can be solved using $O(n)$ blackbox queries, whereas the best known quantum algorithm with fixed order between the gates requires $O(n^2)$ queries. Furthermore, we conjecture that solving this problem in a classical computer takes exponential time, which may be of independent interest.

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Mateus Araújo, Fabio Costa, Časlav Brukner. 2014-01-31. Computational advantage from quantum-controlled ordering of gates. https://doi.org/10.1103/physrevlett.113.250402

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