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Universal continuous-variable quantum computation: Requirement of optical nonlinearity for photon counting

Stephen D. Bartlett·Barry C. Sanders
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Abstract

Although universal continuous-variable quantum computation cannot be achieved via linear optics (including squeezing), homodyne detection and feed-forward, inclusion of ideal photon counting measurements overcomes this obstacle. These measurements are sometimes described by arrays of beam splitters to distribute the photons across several modes. We show that such a scheme cannot be used to implement ideal photon counting and that such measurements necessarily involve nonlinear evolution. However, this requirement of nonlinearity can be moved "off-line," thereby permitting universal continuous-variable quantum computation with linear optics.

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Stephen D. Bartlett, Barry C. Sanders. 2002-03-19. Universal continuous-variable quantum computation: Requirement of optical nonlinearity for photon counting. https://doi.org/10.1103/physreva.65.042304

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