Cooper-Pair Box as a Variable Capacitor
Hanhee Paik, Frederick W. Strauch, Roberto Ramos, A. J. Berkley, Huizhong Xu, S. K. Dutta, Philip R. S. Johnson, Alex J. Dragt, J. R. Anderson, Christopher J. Lobb, F. C. Wellstood · IEEE Transactions on Applied Superconductivity · 2005
We calculate the effective capacitance of a Cooper-pair box and demonstrate that the Cooper-pair box can be used as a variable capacitor. The gate voltage modulates the charge transfer through the small junction in the Cooper-pair box, leading to a gate-dependent capacitance. We describe ongoing experiments to use an Al/AlO/sub x//Al Cooper-pair box as a tunable circuit element at milli-Kelvin temperatures and discuss possible applications to quantum computing as a variable coupling element between two Josephson junction qubits.