A model of magnetic impurities within the Josephson junction of a phase qubit

作者：Erickson R P^*; Pappas D P

来源：Superconductor Science and Technology, 2010, 23(2): 025026.

DOI：10.1088/0953-2048/23/2/025026

We consider a superconducting phase qubit consisting of a monocrystalline sapphire Josephson junction with its symmetry axis perpendicular to the junction interfaces. Via the London gauge, we present a theoretical model of Fe(3+) magnetic impurities within the junction that describes the effect of a low concentration of such impurities on the operation of the qubit. Specifically, we derive an interaction Hamiltonian expressed in terms of angular momentum states of magnetic impurities and low-lying oscillator states of a current-biased phase qubit. We discuss the coupling between the qubit and impurities within the model near resonance. When the junction is biased at an optimal point for acting as a phase qubit, with a phase difference of pi/2 and impurity concentration no greater than 0.05%, we find only a slight decrease in the Q factor of less than 0.01%.

• 出版日期2010-2