Quantum interference enables constant-time quantum information processing

M. Stobińska, A. Buraczewski, M. Moore, W. R. Clements, J. J. Renema, S. W. Nam, T. Gerrits, A. Lita, W. S. Kolthammer, A. Eckstein, I. A. Walmsley

Research output: Working paper

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Science, medicine and engineering demand efficient information processing. It is a long-standing goal to use quantum mechanics to significantly improve such computations. The processing routinely involves examining data as a function of complementary variables, e.g., time and frequency. This is done by the Fourier transform approximations which accurately compute inputs of $2^n$ samples in $O(n 2^n)$ steps. In the quantum domain, an analogous process exists, namely a Fourier transform of quantum amplitudes, which requires exponentially fewer $O(n \log n)$ quantum gates. Here, we report a quantum fractional Kravchuk-Fourier transform, a related process suited to finite string processing. Unlike previous demonstrations, our architecture involves only one gate, resulting in constant-time processing of quantum information. The gate exploits a generalized Hong--Ou--Mandel effect, the basis for quantum-photonic information applications. We perform a proof-of-concept experiment by creation of large photon number states, interfering them on a beam splitter and using photon-counting detection. Existing quantum technologies may scale it up towards diverse applications.
Original languageEnglish
Number of pages44
Publication statusPublished - 11 Jul 2018

Publication series



  • quant-ph

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