Progress in measurement techniques for the single Cooper-pair box qubit

The aluminum single Cooper-pair box (SCB) qubit has demonstrated potential as a candidate for quantum computing. Measurements of coherent manipulation of the relevant SCB states have been demonstrated with various charge and quantum capacitance readout methods. We performed studies of quasiparticle dynamics in an SCB that yielded poisoning probabilities and rates of quasiparticle tunneling processes. Attempts to prevent poisoning with a differential SCB isolated from ground and other quasiparticle sources revealed the possibility for quasiparticle generation on superconducting islands of diminutive size. We have gone on to conduct more advanced measurements of coupled qubits as an important step towards the realization of multi-qubit systems and other precursors that are pivotal in the evolution of reliable quantum computing.