Characterization of a single Cooper pair box

We have used a radio-frequency single electron transistor to read-out a single Cooper pair box. We observe a Coulomb staircase with 2e periodicity, but with a shorter step corresponding to odd number of charges in the box. From the size of this short step we can extract the even–odd energy difference, View the MathML source, and study its magnetic field dependence. We have also characterized the box with microwave spectroscopy and extracted the charging energy and the Josephson coupling energy to be View the MathML source and View the MathML source.