Single Ca/sup +/ ion trapping toward precise frequency measurement of the 4 /sup 2/S/sub 1/2/ - 3/sup 2/D/sub 5/2/ transition

We are proceeding with a development of an optical frequency standard using a ²S_frac12-²D_5/2 electric quadrupole transition of Ca⁺ ions in a small radio-frequency trap. We have theoretically confirmed that an uncertainty of < 1 times 10^-15 is attainable in measurement of the ²S_frac12 - ²D_5/2 transition frequency. Experimentally, we have developed stable laser-diode systems and observed the quantum jump of single ⁴⁰Ca⁺ ions to the ²D_5/2 state