The Quantum Dynamics Research Group focuses on developing novel computational approaches to simulating non-equilibrium dynamics of quantum systems in the condensed phase, overcoming the curse of dimensionality.
Postdoctoral, PhD and project positions are available in our group. Join Us.
March 2024: A novel and efficient approach to incorporating empirical gain / loss mechanisms into numerically exact, non-perturbative path integral simulations of open quantum systems published in the Journal of Physical Chemistry Letters. Check it out…
December 2023: A new tensor network approach to simulating quantum correlation functions published in the Journal of Chemical Physics. Check it out…
September 2023: Study of excitonic dynamics and pathways in the Fenna-Matthews-Olson complex published in the Journal of Physical Chemistry B. Check it out…
August 2023: Work on identifying pathways of quantum transport in molecular aggregates published in the Journal of Chemical Theory and Computation. Check it out…
May 2023: Package for simulating quantum dynamics in complex open systems package with support for a number of state-of-the-art methods published in the Journal of Chemical Physics. Check it out…
The cost of simulations of time-evolution of quantum systems grows exponentially with the number of dimensions involved. Various approaches, both approximate and numerically exact, are required to make such simulations feasible. Explore the ideas that are being developed in the group.
Path integrals offer a robust approach for simulating open quantum dynamics with advancements transcending initial system size limitations. However, accurately modeling systems governed by mechanisms that do not conserve the number of quantum particles, such as lossy cavity modes, remains a challenge. We present a method to incorporate such empirical source and drain mechanisms within a path integral framework using quantum master equations. This technique facilitates rigorous inclusion of bath degrees of freedom while accommodating empirical time scales via Lindbladian dynamics. Computational costs are primarily driven by the path integral method with minimal overhead from Lindbladian terms. We use it to study exciton transport in a four-site Fenna–Matthews–Olson model, examining the potential loss of the exciton to the reaction center. This path integral Lindblad method promises an enhanced ability to simulate dynamics and will be fundamental to simulation of spectra in diverse quantum processes in open systems.
Introducing a novel tensor network approach to computing quantum correlation functions for open quantum systems using Feynman-Vernon influence function. Read in full detail…
The dynamics of the excitation energy transfer (EET) in photosynthetic complexes is an interesting question both from the perspective of fundamental understanding and the research in artificial photosynthesis. Over the past decade, very accurate spectral densities have been developed to capture spatial inhomogeneities in the Fenna–Matthews–Olson (FMO) complex. However, challenges persist in numerically simulating these systems, both in terms of parameterizing them and following their dynamics over long periods of time because of long non-Markovian memories. We investigate the dynamics of FMO with the exact treatment of various theoretical spectral densities using the new tensor network path integral-based methods, which are uniquely capable of addressing the difficulty of long memory length and incoherent Förster theory. It is also important to be able to analyze the pathway of EET flow, which can be difficult to identify given the non-trivial structure of connections between bacteriochlorophyll molecules in FMO. We use the recently introduced ideas of relating coherence to population derivatives to analyze the transport process and reveal some new routes of transport. The combination of exact and approximate methods sheds light on the role of coherences in affecting the fine details of the transport and promises to be a powerful toolbox for future exploration of other open systems with quantum transport.
Understanding the pathways taken by a quantum particle during a transport process is an enormous challenge. There are broadly two different aspects of the problem that affect the route taken. First is obviously the couplings between the various sites, which translates into the intrinsic “strength” of a state-to-state channel. Apart from these inter-state couplings, the relative coupling strengths and timescales of the solvent modes form the second factor. This impact of the dissipative environment is significantly more difficult to analyze. Building on the recently derived relations between coherences and population derivatives, we present an analysis of the transport that allows us to account for both the effects in a rigorous manner. We demonstrate the richness hidden behind the transport even for a relatively simple system, a 4-site coarse-grained model of the Fenna–Matthews–Olson complex. The effect of the local dissipative media is highly nontrivial. We show that while the impact on the total site population may be small, there are noticeable changes to the pathway taken by the transport process. We also demonstrate how an analysis in a similar spirit can be done using the Förster approximation. The ability to untangle the dynamics at a greater granularity opens up possibilities in terms of design of novel systems with an eye toward quantum control.