Probing electronic decoherence with high-resolution attosecond photoelectron interferometry

Quantum coherence plays a fundamental role in the study and control of ultrafast dynamics in matter. In the case of photoionization, entanglement of the photoelectron with the ion is a well-known source of decoherence when only one of the particles is measured. Here, we investigate decoherence due to entanglement of the radial and angular degrees of freedom of the photoelectron. We study two-photon ionization via the 2s2p autoionizing state in He using high spectral resolution photoelectron interferometry. Combining experiment and theory, we show that the strong dipole coupling of the 2s2p and 2p(2) states results in the entanglement of the angular and radial degrees of freedom. This translates, in angle-integrated measurements, into a dynamic loss of coherence during autoionization.

Automated summary

Quantum coherence is crucial in the study of ultrafast dynamics in matter, but in the case of photoionization, entanglement causes decoherence. This study investigates the decoherence resulting from the entanglement of the radial and angular degrees of freedom of the photoelectron. It is shown through experiment and theory that the strong dipole coupling between the 2s2p and 2p(2) states in He leads to entanglement and subsequent loss of coherence in angle-integrated measurements during autoionization.