Effect of measurement on the periodicity of the Coulomb staircase of a superconducting box.
We report on the effect of the backaction of a single Cooper pair transistor electrometer (E) on the charge state of a superconducting box (B). The charge is e periodic in the gate bias of B when E is operated near voltages 2 Delta/e or 4 Delta/e. We show that this is due to quasiparticle poisoning of B at a rate proportional to the number of quasiparticle tunneling events in E per second. We are able to eliminate this backaction and recover 2e-charge periodicity using a new measurement method based on switching-current modulation of E.
Männik
J
J
Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800, USA.
Lukens
J E
JE