# Robust two-level system control by a detuned and chirped laser pulse

## TL;DR

This paper introduces a robust control method for two-level quantum systems using ultrafast chirped laser pulses, demonstrating resilience to power fluctuations through numerical and experimental validation.

## Contribution

It presents a novel, simple control scheme employing nonadiabatic chirped pulses that achieves robustness against power fluctuations in two-level systems.

## Key findings

- Numerical evidence of robustness against power fluctuations.
- Experimental demonstration with cold atoms using femtosecond lasers.
- Identification of a cusp on the Bloch sphere indicating optimal control.

## Abstract

We propose and demonstrate a robust control scheme by ultrafast nonadiabatic chirped laser pulse, designed for targeting coherent superpositions of two-level systems. Robustness against power fluctuation is proved by our numerical study and a proof-of-principle experiment performed with femtosecond laser interaction on cold atoms. They exhibit for the final driven dynamics a cusp on the Bloch sphere, corresponding to a zero curvature of fidelity. This solution is particularly simple and thus applicable to a wide range of potential applications.