Population-resolved measurement of an avoided crossing of light-dressed states

TL;DR

This paper presents a novel experimental technique to measure both the energy levels and population amplitudes of light-dressed states in a two-level atomic system, providing deeper insight into quantum state compositions.

Contribution

It introduces a population-resolved measurement method for avoided crossings in light-dressed states, extending beyond traditional spectroscopic energy measurements.

Findings

Resolved population amplitudes of light-dressed states

Demonstrated measurement in Rydberg states of cold rubidium

Provided detailed insight into eigenvector compositions

Abstract

A two-level system coupled by a coherent field is a ubiquitous system in atomic and molecular physics. In the rotating wave approximation, the light-dressed states are well described by a simple 2x2 Hamiltonian which can be easily solved analytically and is thus used in quantum mechanics education and as a basis for intuition for more complicated systems. The solution to the Hamiltonian is an avoided crossing between the light-dressed ground and excited states. In experiments, the avoided crossing is probed spectroscopically, meaning only the energies, or eigenvalues of the Hamiltonian, are measured. Here, we present a measurement of the avoided crossing which also resolves population, thus indicating the amplitude coefficients of the eigenvectors of the Hamiltonian. We perform the measurement in Rydberg states of cold rubidium atoms, resolving the energies spectroscopically with our pump lasers and the populations of each state using selective field ionization.