Molecular Entanglement Witness by Absorption Spectroscopy in Cavity QED

TL;DR

This paper proposes a protocol using absorption spectroscopy in cavity QED to detect multipartite molecular entanglement at room temperature, leveraging quantum Fisher information as an entanglement witness.

Contribution

It generalizes the quantum Fisher information-based entanglement witness for non-identical local responses and links it to absorption spectroscopy for practical detection.

Findings

Quantum Fisher information effectively witnesses inter-molecular entanglement.

The entanglement witness works near the superradiant phase transition.

Detection protocol applicable to room temperature chemical systems.

Abstract

Producing and maintaining molecular entanglement at room temperature and detecting multipartite entanglement features of macroscopic molecular systems remain key challenges for understanding inter-molecular quantum effects in chemistry. Here, we study the quantum Fisher information, a central concept in quantum metrology, as a multipartite entanglement witness. We generalize the entanglement witness functional related to quantum Fisher information regarding non-identical local response operators. We show that it is a good inter-molecular entanglement witness for ultrastrong light-matter coupling in cavity quantum electrodynamics, including near the superradiant phase transition. We further connect quantum Fisher information to the dipole correlator, which suggests that this entanglement could be detected by absorption spectroscopy. Our work proposes a general protocol to detect inter-molecular entanglement in chemical systems at room temperature.