Quantum Correlation and Synchronisation-Enhanced Energy Transfer in Driven-Dissipative Light-Harvesting Dimers

TL;DR

The paper addresses the robustness of quantum synchronisation as a mechanism for excitonic energy transfer in driven-dissipative light-harvesting dimers. It adopts an open quantum-system framework for an exciton–vibrational dimer and compares full quantum dynamics with semiclassical rate equations, revealing that non-negligible quantum correlations between electronic and vibrational degrees are essential for synchronisation and transfer. A nonlinear, non-Condon modulation of the dipole–dipole interaction—the environment-assisted transfer channel—enables long-lived coherence and sustained energy flow under continuous pumping. In driven-dissipative steady states, this mechanism yields high phase coherence (PLV near unity) alongside persistent energy transfer, suggesting a general principle for robust transport in dissipative molecular systems. The results point toward design principles for bio-inspired energy transport and motivate exploration of larger chromophore networks and 2DES signatures of vibronic coherence.

Abstract

Quantum synchronisation has recently been proposed as a mechanism for electronic excitation energy transfer in light-harvesting complexes, yet its robustness in driven-dissipative settings remains under active investigation. Here, we revisit this mechanism in cryptophyte photosynthetic antennae using an exciton--vibrational dimer model. By comparing the full open quantum dynamics with semi-classical rate equations for electronic density-matrix elements and vibrational observables, we demonstrate that quantum correlations between electronic and vibrational degrees of freedom, beyond the semi-classical factorised limit, underpin the emergence of quantum synchronisation. Furthermore, we introduce an environment-assisted transfer mechanism arising as a nonlinear, non-Condon correction to the dipole--dipole interaction. This mechanism enables long-lived quantum coherence and continuous, synchronisation-enhanced energy transfer in a driven-dissipative regime, thereby suggesting new avenues for investigating photosynthetic energy-transfer dynamics.

Figures (4)

• Figure 1: Schematic illustration of an exciton–vibrational dimer weakly coupled to its environment, including vibronic relaxation and electronic dephasing channels with rates $\Gamma_{\rm th}$ and $\Gamma_{\rm deph}$, receptively. The additional rate $\Gamma_{\rm dip}$ denotes the introduced environment-assisted contribution to the dipole--dipole interaction.
• Figure 2: Numerical simulation of Eq. \ref{['eq:froster_eom']} under various conditions. The left column of subplots considers the case with vibronic dissipation only, while the right one further includes $\hat{\sigma}_m$ electronic dephasing. The first row depicts the density matrix populations of electronic states. The second row plots $\expval*{\hat{b}_m^{\dagger}+\hat{b}_m}$, and the last row shows the moving PLV of a time window 0.1 ps over the 100 ps simulation. The negative values of $\expval*{\hat{b}_m^{\dagger}+\hat{b}_m}$ have been discarded for logarithmic scales on the vertical axes. Parameters used in the simulation can be found in Table. (\ref{['tab:1']}).
• Figure 3: Numerical simulation of the quantum dynamics (\ref{['eq:system']}) with $\hat{\sigma}_m$ electronic dephasing compared to classical ODE simulation. The first row shows electronic density matrix elements. The second and third rows depict $\expval*{\hat{b}_m^{\dagger}+\hat{b}_m}$ and ${\rm i}\expval*{\hat{b}_m^{\dagger}-\hat{b}_m}$, respectively. The last row plots the quantum correlations $\Delta C_m\equiv \expval*{\op{m}}\expval*{\hat{b}_m^{\dagger}+\hat{b}_m}-\expval*{\op{m}(\hat{b}_m^{\dagger}+\hat{b}_m)}$ due to the factorised-state approximation \ref{['eq:factorized']}. Parameters used can be found in Table. (\ref{['tab:1']}).
• Figure 4: Numerical simulation of the environment-assisted energy transfer process. The first row shows the electronic populations of the single excited states, expected displacements $\expval*{\hat{b}_m^{\dagger}+\hat{b}_m}$, and corresponding PLVs, from left to right, respectively. The second row zooms in on the electronic populations during the first 0.5 ps. Instead of using $\Delta\varepsilon$ in Table. (\ref{['tab:1']}), we use real site energies, $\varepsilon_1=19574$ and $\varepsilon_2=18532$, assume the double excitation energy to be 60000, which is large enough to keep the Heitler--London approximation valid ($\rho_{00}=0$) and allows us to focus only on the single excited states (all in units of cm$^{-1}$). The Rabi frequency is taken to be $\Omega=200$ THz, the environment-assistant rate is $\Gamma_{\rm dip} = 10$ THz, and the electronic dephasing rate is now $\Gamma_{\rm deph} = 0.1$ THz.