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A conditional-phase switch at the single-photon level

K. J. Resch·J. S. Lundeen·A. M. Steinberg
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Abstract

We present an experimental realization of a two-photon conditional-phase switch, related to the ``$c$-$ϕ$'' gate of quantum computation. This gate relies on quantum interference between photon pairs, generating entanglement between two optical modes through the process of spontaneous parametric down-conversion (SPDC). The interference effect serves to enhance the effective nonlinearity by many orders of magnitude, so it is significant at the quantum (single-photon) level. By adjusting the relative optical phase between the classical pump for SPDC and the pair of input modes, one can impress a large phase shift on one beam which depends on the presence or absence of a single photon in a control mode.

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K. J. Resch, J. S. Lundeen, A. M. Steinberg. 2002-05-17. A conditional-phase switch at the single-photon level. https://doi.org/10.1103/physrevlett.89.037904

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