title: Generation of a decoherence-free entangled state using a radio-frequency dressed state.
abstract: We propose the generation of entangled states with trapped calcium ions using a combination of an rf dressed state and a spin-dependent force. By using this method, a decoherence-free entangled state of rf qubits can be directly generated, and ideally its fidelity is close to unity. We demonstrate an rf entangled state with a fidelity of 0.68±0.08, which has a coherence time of more than 200 ms by virtue of the fact that it is an eigenstate with energy gaps between adjacent levels. Using the same technique, we also produce a qutrit-qutrit entangled state with a fidelity of 0.77±0.09, which exceeds the threshold value for separability of 2/3.
authors.affiliation: Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan. noguchi@qe.ee.es.osaka-u.ac.jp
authors.forename: Atsushi
authors.initials: A
authors.lastname: Noguchi
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Haze
authors.forename: Kenji
authors.initials: K
authors.lastname: Toyoda
authors.forename: Shinji
authors.initials: S
authors.lastname: Urabe