Maximizing Hole Coherence in Ultrafast Photoionization of Argon with SPA-Optimization

TL;DR

This paper introduces SPA-optimization, a derivative-free quantum control method, to maximize hole state coherence in ultrafast argon photoionization, enabling tailored superpositions with practical constraints.

Contribution

The paper presents SPA-optimization, a novel derivative-free method for quantum control, applied to optimize hole coherence in argon photoionization with shaped attosecond pulses.

Findings

Maximized hole coherence between 3s and 3p0 states.

Achieved control over hole population ratios.

Demonstrated computational efficiency of SPA-optimization.

Abstract

Photoionization with attosecond pulses populates hole states in the photoion. Superpositions of hole states represent ideal candidates for time-dependent spectroscopy, for example via pump-probe studies. The challenge consists in identifying pulses that create coherent superpositions of hole states while satisfying practical constraints. Here, we employ quantum optimal control to maximize the degree of coherence between these hole states. To this end, we introduce a derivative-free optimization method with Sequential PArametrization update (SPA-optimization). We demonstrate the versatility and computational efficiency of SPA-optimization for photoionization in argon by maximizing the coherence between the $3s$ and $3p_0$ hole states using shaped attosecond pulses. We show that it is possible to maximize the hole coherence while simultaneously prescribing the ratio of the final hole state populations.