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Quantum Entanglement-Enhanced Spectroscopy for Probing Coherent Dynamics in Complex Chemical Systems

Revista, Zen, CHEMISTRY, 10

Published Nov 28, 2025• 0 citations
Publisher

Abstract

Quantum entanglement, a hallmark of quantum mechanics, offers unprecedented opportunities to revolutionize spectroscopic techniques. This paper explores the theoretical underpinnings and experimental prospects of quantum entanglement-enhanced spectroscopy for the precise probing of coherent dynamics in complex chemical systems. Traditional spectroscopic methods often face limitations in resolution, sensitivity, and the ability to distinguish subtle quantum phenomena due to their reliance on classical light sources. By harnessing entangled photons, it is possible to overcome these limitations, enabling sub-shot-noise measurements, enhanced spectral resolution beyond the diffraction limit, and access to non-classical correlations within molecular systems. We delve into how entangled light can be generated and engineered to interact with molecular ensembles, facilitating the study of processes such as exciton transport, charge transfer, and vibrational energy redistribution with extraordinary fidelity. The methodology section outlines conceptual experimental setups, including entangled two-photon absorption spectroscopy and quantum Ramsey interferometry, discussing the benefits of these approaches over their classical counterparts. We present hypothetical results demonstrating how entanglement can resolve overlapping spectral features, extend coherence lifetimes, and provide unique insights into the quantum pathways governing chemical reactions. The discussion addresses the challenges associated with maintaining entanglement in noisy chemical environments and outlines strategies for mitigating decoherence. Ultimately, entanglement-enhanced spectroscopy represents a transformative paradigm for chemical physics, promising a deeper understanding of fundamental quantum processes that dictate reactivity and function in biological and material sciences.

DOI
10.5281/zenodo.17743474

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Nonlinear spectroscopic techniques using entangled photon pairs can provide an opportunity to exploit non-classical correlations encoded in two-photon wavefunctions to manipulate two-exciton wavefunctions. We propose an entangled photon pair-enhanced multidimensional spectroscopic technique that is sensitive to exciton-exciton interactions and correlations at the femtosecond timescale. Simulations for a dissipative system, namely, the photosynthetic aggregate reveal the superior ability of entangled photon pairs, compared to both transform-limited and frequency-chirped laser pulses, to manipulate excited-state absorption pathways. The corresponding spectral features in the two-dimensional spectrogram are interpreted in terms of one- and two-exciton resonances. The signal scales linearly with the incoming intensity of the photon sources. We show that classifying these resonances using entangled photon source in the perturbative limit allow for probing exciton correlations at the natural energy scale. These insights can be used to explore multi-exciton dynamics in molecular systems using multiphoton entanglement.
In this talk, I will discuss the growing field of entangled-photon spectroscopy as related to mol. systems. An entangled \nstate is represented by a wavefunction, describing a group of particles, which cannot be factored into sep. states of \nindividual particles. For photons, these correlations lead to non-classical light-matter interactions, potentially creating new opportunities for spectroscopic techniques. For example, second-order processes with two entangled photons, such as two-photon absorption or sum frequency generation, occur at a linear rate with a cross section that should be close to that of one-photon classical processes. However, early results in the field have produced conflicting measurements as to its magnitude. I will discuss the role of excited state dephasing and time-ordering for entangled photon interactions. I will also briefly remark on other interesting prospects of entangled photons, such as their ability to break the temporal-spectral Fourier transform limit. For instance, few-femtosecond spectroscopy is predicted to be possible with entangled light sources of MHz linewidths. Given the entangled photons quantum correlations, this property may lead to interesting opportunities in directing quantum coupled quantum states, although the techniques are still at an early stage.