Optimization of Junction and Bias Parameters in readout of Phase Qubit

Abstract

The exact numerical solution of the nonlinear Ginzburg-Landau equation for Josephson junctions is obtained, from which the nontrivial current density and effective potential of the Josephson junction are accurately found. Tunneling probabilities of the calculated bound states in the resulting potential well are computed. The effects of junction and bias parameters such as thickness of the insulating barrier, cross sectional area, bias current and magnetic field are fully investigated using a successive perturbation approach. We define and compute figures of merit for achieving optimal operation of phase qubits and measurement of states. Particularly, it is predicted that Josephson junctions with thicker barriers yield better performance in measurement of the phase qubit. The proportion of other parameters is also studied and discussed for the right situation of the setup. Results are in complete agreement with reported experimental data.