title: Spectroscopic Evidence of the Aharonov-Casher Effect in a Cooper Pair Box.
abstract: We observe the effect of the Aharonov-Casher (AC) interference on the spectrum of a superconducting system containing a symmetric Cooper pair box (CPB) and a large inductance. By varying the charge n_{g} induced on the CPB island, we observe oscillations of the device spectrum with the period Δn_{g}=2e. These oscillations are attributed to the charge-controlled AC interference between the fluxon tunneling processes in the CPB Josephson junctions. The measured phase and charge dependences of the frequencies of the |0⟩→|1⟩ and |0⟩→|2⟩ transitions are in good agreement with our numerical simulations. Almost complete suppression of the single fluxon tunneling due to destructive interference is observed for the charge n_{g}=e(2n+1). The CPB in this regime enables fluxon pairing, which can be used for the development of parity-protected superconducting qubits.
authors.affiliation: Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA.|Department of Electrical Engineering, University of Massachusetts, Boston, Massachusetts 02125, USA.
authors.forename: M T
authors.initials: MT
authors.lastname: Bell
authors.affiliation: Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA.
authors.forename: W
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA.|LPTHE, CNRS UMR 7589, 4 place Jussieu, 75252 Paris, France.
authors.forename: L B
authors.initials: LB
authors.lastname: Ioffe
authors.affiliation: Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA.
authors.forename: M E
authors.initials: ME
authors.lastname: Gershenson