Attosecond Entangled Photons from Two-Photon Decay of Metastable Atoms: A Source for Attosecond Experiments and Beyond

TL;DR

This paper proposes a novel method to generate attosecond entangled photon pairs via two-photon decay in metastable helium, offering a new source for ultrafast experiments and potential to explore zeptosecond dynamics.

Contribution

It introduces a new atomic decay-based source of entangled bi-photons in the attosecond regime for ultrafast quantum optics applications.

Findings

Calculated bi-photon generation rate from helium decay.

Demonstrated suitability for attosecond pump-probe experiments.

Discussed potential to reach zeptosecond time scales.

Abstract

We propose the generation of attosecond entangled bi-photons in the extreme-ultraviolet regime by two-photon decay of a metastable atomic state as a source similar to spontaneous parametric down-conversion photons. The 1s2s $^1S_0$ metastable state in helium decays to the ground state by emission of two energy-time entangled photons with a photon bandwidth equal to the total energy spacing of 20.62 eV. This results in a pair correlation time in the attosecond regime making these entangled photons a highly suitable source for attosecond pump-probe experiments. The bi-photon generation rate from a direct four photon excitation of helium at 240 nm is calculated and used to assess some feasible schemes to generate these bi-photons. Possible applications of entangled bi-photons in attosecond time scale experiments, and a discussion of their potential to reach the zeptosecond regime are presented.