A conditional-phase switch at the single-photon level

Abstract

We present an experimental realization of a two-photon conditional-phase switch, related to the ``$c$-$\varphi$'' 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.

8 pages, 4 figures

References in corpus (2)

• Experimental quantum teleportation
• Nonlinear optics with less than one photon

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