Toward witnessing molecular exciton entanglement from spectroscopy

Journal Article · Wed Oct 20 00:00:00 EDT 2021 · Physical Review A

DOI:https://doi.org/10.1103/physreva.104.042416· OSTI ID:1979600

Sifain, Andrew E. ^[1]; Fassioli, Francesca ^[2]; Scholes, Gregory D. ^[3]

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1. Princeton University, NJ (United States); OSTI
2. Princeton University, NJ (United States); Scoula Internazionale Superiore di Studi Avanzati, Trieste (Italy)
3. Princeton University, NJ (United States)

Entanglement is a defining feature of quantum mechanics that can be a resource in engineered and natural systems, but measuring entanglement in experiment remains elusive especially for large chemical systems. Most practical approaches require determining and measuring a suitable entanglement witness which provides some level of information about the entanglement structure of the probed state. A fundamental quantity of quantum metrology is the quantum Fisher information (QFI), which is a rigorous witness of multipartite entanglement that can be evaluated from linear response functions for certain states. Here, in this paper, we explore measuring the QFI of molecular exciton states of the first-excitation subspace from spectroscopy. In particular, we utilize the fact that the linear response of a pure state subject to a weak electric field over all possible driving frequencies encodes the variance of the collective dipole moment in the probed state, which is a valid measure for QFI. The systems that are investigated include the molecular dimer, N-site linear aggregate with nearest-neighbor coupling, and N-site circular aggregate, all modeled as a collection of interacting qubits. Our theoretical analysis shows that the variance of the collective dipole moment in the brightest dipole-allowed eigenstate is the maximum QFI. The optical response of a thermally equilibrated state in the first-excitation subspace is also a valid QFI. Theoretical predictions of the measured QFI for realistic linear dye aggregates as a function of temperature and energetic disorder due to static variations of the host matrix show that two- to three-partite entanglement is realizable. This paper lays some groundwork and inspires measurement of multipartite entanglement of molecular excitons with ultrafast pump-probe experiments.

• Research Organization: Boston University, MA (United States); Princeton University, NJ (United States)
• Sponsoring Organization: European Union’s H2020; Gordon and Betty Moore Foundation; USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0020437
• OSTI ID: 1979600
• Journal Information: Physical Review A, Journal Name: Physical Review A Journal Issue: 4 Vol. 104; ISSN 2469-9926
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
electronic transitions
light-matter interaction
molecular spectra
quantum correlations in quantum information
quantum entanglement