Trapping and cooling of ions for quantum information processing

In quantum networks quantum information is processed by exchanging quantum states between physical systems. We have studied trapping and cooling of ions for quantum information processing to build a prototype of the quantum network. We have found ⁴³Ca ⁺ as the best candidate for the qubit in the quantum network. The schemes for quantum gate operations and for quantum state transfer with the ion species are discussed. We have developed a ring ion trap and a light source consisting of violet diode lasers for realizing the schemes. We have achieved deterministic coupling of a single ⁴⁰Ca ⁺ to the optical field in a cavity.