PARITY FLUCTUATIONS BETWEEN COULOMB BLOCKADED SUPERCONDUCTING ISLANDS

We find that if two superconducting islands of different number parity are linked by a tunnel junction, the unpaired electron in the odd isl and has a tendency to tunnel into the even island. This process leads to fluctuations in time of the number parity of each island, giving ri se to a random telegraph noise spectrum with a characteristic frequenc y that has an unusual temperature dependence. This new phenomenon shou ld be observable in a Cooper-pair pump and similar single-electron tun neling devices.