Cooper-pair box as a variable capacitor

• Published in: IEEE transactions on applied superconductivity Vol. 15; no. 2; pp. 884 - 887
• Main Authors: Paik, H., Strauch, F.W., Ramos, R.C., Berkley, A.J., Xu, H., Dutta, S.K., Johnson, P.R., Dragt, A.J., Anderson, J.R., Lobb, C.J., Wellstood, F.C.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01.06.2005; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Aluminum; Applied sciences; Capacitance; Capacitors; Capacitors. Resistors. Filters; Charge transfer; Computer applications; Cooper-pair box; Coupling circuits; Electrical engineering. Electrical power engineering; Exact sciences and technology; Josephson junction; Josephson junctions; Mathematical analysis; Quantum capacitance; Quantum computing; qubit; Qubits (quantum computing); Superconductivity; Temperature; Tunable circuits and devices; variable capacitor; Various equipment and components; Voltage; Tunable circuit; Cooper-pair box; Quantum computation; Variable capacitor; Gate voltage; Josephson junction; qubit; Cooper pair; Capacitance; Quantum information; Experimental study; Charge transfer
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2005.850100

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.