Engineering of the qubit initialization in an imperfect physical system

TL;DR

This paper introduces a robust inverse engineering method for qubit initialization that enhances fidelity, reduces excitation time, and is adaptable to various physical systems despite imperfections and inhomogeneities.

Contribution

The authors develop a pulse engineering technique combining multiple degrees of freedom and perturbation theory to improve qubit initialization robustness and efficiency.

Findings

Initialization more robust against laser intensity variations

Reduces intermediate state occupation by a factor of 17

Applicable to diverse quantum systems like NV centers and superconducting qubits

Abstract

We proposed a method to engineer the light matter interaction while initializing a qubit in presence of physical constraints utilizing the inverse engineering. Combining the multiple degrees of freedom in the pulse parameters with the perturbation theory, we developed pulses to initialize the qubit within a tightly packed frequency interval to an arbitrary superposition state with high fidelity. Importantly, the initialization induces low off-resonant excitations to the neighboring qubits, and it is robust against the spatial inhomogeneity in the laser intensity. We applied the method to the ensemble rare-earth ions system, and simulations show that the initialization is more robust against the variations in laser intensity than the previous pulses, and reduces the time that ions spend in the intermediate excited state by a factor of 17. The method is applicable to any systems addressed in frequency such as NV centers, superconducting qubits, quantum dots, and molecular qubit systems.