Population transfer between two quantum states by piecewise chirping of femtosecond pulses: Theory and experiment

TL;DR

This paper introduces a novel method for quantum state population transfer using a train of ultrashort laser pulses, demonstrating its effectiveness and robustness both theoretically and experimentally on Rubidium atoms.

Contribution

The paper presents a new piecewise adiabatic passage technique with pulse train control for robust quantum state transfer, extending traditional single-pulse methods.

Findings

Complete population transfer achieved in Rubidium atoms.

Method is insensitive to total excitation energy under adiabatic conditions.

Experimental demonstration confirms theoretical predictions.

Abstract

We propose and demonstrate the method of population transfer by piecewise adiabatic passage between two quantum states. Coherent excitation of a two-level system with a train of ultrashort laser pulses is shown to reproduce the effect of an adiabatic passage, conventionally achieved with a single frequency-chirped pulse. By properly adjusting the amplitudes and phases of the pulses in the excitation pulse train, we achieve complete and robust population transfer to the target state. The effect is demonstrated experimentally by observing piecewise excitation of Rubidium atoms from 5s_1/2 to 5p_1/2 electronic state. We show that similarly to the conventional adiabatic passage, the piecewise process is insensitive to the total excitation energy as long as the adiabaticity conditions are satisfied. The piecewise nature of the process suggests that robust and selective population transfer could be implemented in a variety of complex quantum systems beyond the two-level approximation.