arXiv subjects

Matteo Bruschi

Publications and source records attributed to Matteo Bruschi.

5 recordsLinked to original sources

arXiv2026

Simulating spectrally resolved exciton--exciton-interaction pump--probe spectroscopy

Exciton--exciton-interaction pump--probe spectroscopy (EEI--PP) captures the fifth-order signal of light-matter interaction, directly probing exciton--exciton annihilation. This allows studying excitation energy transport even in extended, nearly isoenergetic landscapes. Although spectrally resolved fifth-order signals have already been explored in simplified cases, in larger systems only spectrally integrated signals have been analyzed. We present a microscopic theoretical description for spectrally resolved EEI--PP response with realistic lineshapes, revealing how single- and multi-exciton state structure shape the spectral features and dynamics. The description is applicable to large molecular systems such as squaraine polymers, facilitating a direct comparison with experimental spectra. By a decomposition of the total signal into individual excitation pathways, we demonstrate that the spectral resolution is needed to distinguish otherwise intertwined single- and multi-exciton dynamics, such as single-exciton relaxation and exciton--exciton annihilation.

physics.chem-ph↗

arXiv2025

Influence of excitonic coupling, static disorder, and coherent dynamics in action-2D electronic spectroscopy of a molecular dimer model

We investigate the spectral features of Action-2D Electronic Spectroscopy (A-2DES) in a molecular dimer model across different regimes of excitonic coupling. By explicitly including a second-excited state for each chromophore, we simulate A-2DES spectra ranging from the non-interacting limit to the strong-coupling case, focusing on the significance of cross peaks. While for weak excitonic coupling, cross peaks can be understood as the incoherent mixing of linear signals of the two chromophores, these features reflect excitonic delocalization as the coupling increases. We highlight that A-2DES offers enhanced sensitivity to coherent excited-state dynamics, particularly in the intermediate-coupling regime, where it provides higher contrast compared to its coherent-detected counterpart. Finally, we show that static disorder reduces the relative amplitude of cross peaks compared to diagonal features in a way that depends on the excitonic coupling. Notably, the relative suppression of cross peaks decreases with the strength of the excitonic coupling, implying that spectral features related to incoherent mixing are less prominent in inhomogeneous samples. These findings support the potential of A-2DES for investigating excitonic dynamics in small multi-chromophoric systems.

physics.chem-ph↗

arXiv2024

Simulating Non-Markovian Dynamics in Multidimensional Electronic Spectroscopy via Quantum Algorithm

Including the effect of the molecular environment in the numerical modeling of time-resolved electronic spectroscopy remains an important challenge in computational spectroscopy. In this contribution, we present a general approach for the simulation of the optical response of multi-chromophore systems in a structured environment and its implementation as a quantum algorithm. A key step of the procedure is the pseudomode embedding of the system-environment problem resulting in a finite set of quantum states evolving according to a Markovian quantum master equation. This formulation is then solved by a collision model integrated into a quantum algorithm designed to simulate linear and nonlinear response functions. The workflow is validated by simulating spectra for the prototypical excitonic dimer interacting with fast (memoryless) and finite-memory environments. The results demonstrate, on the one hand, the potential of the pseudomode embedding for simulating the dynamical features of nonlinear spectroscopy, including lineshape, spectral diffusion, and relaxations along delay times. On the other hand, the explicit synthesis of quantum circuits provides a fully quantum simulation protocol of nonlinear spectroscopy harnessing the efficient quantum simulation of many-body dynamics promised by the future generation of fault-tolerant quantum computers.

quant-ph↗

arXiv2024

From Stochastic Hamiltonian to Quantum Simulation: Exploring Memory Effects in Exciton Dynamics

The unraveling of open quantum system dynamics in terms of stochastic quantum trajectories offers a picture of open system dynamics that consistently considers memory effects stemming from the finite correlation time of environment fluctuations. These fluctuations significantly influence the coherence and energy transport properties of excitonic systems. When their correlation time is comparable to the timescale of the Hamiltonian evolution, it leads to the departure of open system dynamics from the Markovian limit. In this work, we leverage the unraveling of exciton dynamics through stochastic Hamiltonian propagators to design quantum circuits that simulate exciton transport, capturing finite memory effects. In addition to enabling the synthesis of parametrizable quantum circuits, stochastic unitary propagators provide a transparent framework for investigating non-Markovian effects on exciton transport. Our analysis reveals a nuanced relationship between environment correlation time and transport efficiency, identifying a regime of "memory-assisted" quantum transport where time-correlated fluctuations allow the system to reach higher efficiency. However, this property is not universal and can only be realized in conjunction with specific features of the system Hamiltonian.

quant-ph↗

arXiv2021

Strategies to simulate dephasing-assisted quantum transport on digital quantum computers

Simulating charge and energy transfer in extended molecular networks requires an effective model to include the environment because it significantly affects the quantum dynamics. A prototypical effect known as Environment-Assisted Quantum Transport (ENAQT) consists in the modulation and sometimes enhancement of the transfer efficiency by the interaction with an environment. A simple description of this phenomenon is obtained by a quantum master equation describing a quantum walk over the molecular network in the presence of inter-site decoherence. We consider the problem of simulating the dynamics underlying ENAQT in a digital quantum computer. Two different quantum algorithms are introduced, the first one based on stochastic Hamiltonians and the second one based on a collision scheme. We test both algorithms by simulating ENAQT in a small molecular network on a quantum computer emulator and provide a comparative analysis of the two approaches. Both algorithms can be implemented in a memory efficient encoding with the number of required qubits scaling logarithmically with the size of the simulated system while the number of gates increases quadratically. We discuss the algorithmic quantum trajectories generated by the two simulation strategies showing that they realize distinct unravellings of the site-dephasing master equation. In our approach, the non-unitary dynamics of the open system is obtained through effective representations of the environment, paving the way to digital quantum simulations of quantum transport influenced by structured environments.

quant-ph↗