Optimization of Junction and Bias Parameters in readout of Phase Qubit

TL;DR

This paper presents a detailed numerical analysis of Josephson junctions, optimizing parameters like barrier thickness and bias current to improve phase qubit measurement, aligning well with experimental results.

Contribution

It introduces an exact numerical solution to the nonlinear Ginzburg-Landau equation for Josephson junctions and identifies optimal parameters for phase qubit performance.

Findings

Thicker barriers improve measurement accuracy of phase qubits.

Optimal bias and junction parameters enhance qubit operation.

Results agree with experimental data.

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.