Abstract

We report on the demonstration of ion–photon entanglement and Bell inequality violation in a system of trapped ${{}^{138}\mathrm{Ba}}^{+}$ ions. Entanglement between the Zeeman sublevels of the ground state of a single ${{}^{138}\mathrm{Ba}}^{+}$ ion and the polarization state of a single 493 nm photon emitted by the ion with a fidelity of $0.84\pm 0.01$ was achieved, along with a Bell signal of 2.3, exceeding the classical limit of 2 by more than eight standard deviations. This system is a promising candidate for a loophole-free Bell inequality violation test using long-range ion–ion entanglement as the wavelengths of the transitions of ${{}^{138}\mathrm{Ba}}^{+}$ are in the visible region and thus suitable for long-range transmission over fiber optic cable.

© 2014 Optical Society of America

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