Optimized single-qubit gates for Josephson phase qubits

TL;DR

This paper uses quantum optimal control theory to design high-fidelity single-qubit gates for Josephson phase qubits by optimizing bias current modulations, considering experimental imperfections and interactions.

Contribution

It introduces a method to optimize bias current pulses for Josephson qubits, enhancing gate fidelity and robustness against imperfections and qubit interactions.

Findings

Optimized pulses achieve higher gate fidelity.

Robustness against pulse shape imperfections demonstrated.

Effects of off-resonance and capacitive coupling analyzed.

Abstract

In a Josephson phase qubit the coherent manipulations of the computational states are achieved by modulating an applied ac current, typically in the microwave range. In this work we show that it is possible to find optimal modulations of the bias current to achieve high-fidelity gates. We apply quantum optimal control theory to determine the form of the pulses and study in details the case of a NOT-gate. To test the efficiency of the optimized pulses in an experimental setup, we also address the effect of possible imperfections in the pulses shapes, the role of off-resonance elements in the Hamiltonian, and the effect of capacitive interaction with a second qubit.