State Flip at Exceptional Points in Atomic Spectra

TL;DR

This paper investigates the behavior of non-adiabatic population transfer at exceptional points in the hydrogen atom's spectrum, revealing conditions under which typical adiabatic assumptions break down and exploring higher-order exceptional points.

Contribution

It provides a realistic quantum system analysis of population transfer at exceptional points, including third-order cases, and examines the limits of the non-adiabatic hypothesis.

Findings

Encircling an exceptional point leads to the system ending in the same state regardless of initial conditions.

Non-adiabatic hypothesis can be violated when nearby resonances are considered.

Analysis of third-order exceptional points involving three resonances.

Abstract

We study the behavior of the non-adiabatic population transfer between resonances at an exceptional point in the spectrum of the hydrogen atom. It is known that, when the exceptional point is encircled, the system always ends up in the same state, independent of the initial occupation within the two-dimensional subspace spanned by the states coalescing at the exceptional point. We verify this behavior for a realistic quantum system, viz. the hydrogen atom in crossed electric and magnetic fields. It is also shown that the non-adiabatic hypothesis can be violated when resonances in the vicinity are taken into account. In addition, we study the non-adiabatic population transfer in the case of a third-order exceptional point, in which three resonances are involved.