The interparticle Coulombic decay process (ICD) in a Coulomb-coupled pair of quantum dots (QDs) was predicted to feature electronic relaxation within one QD in conjunction with ionization of the other. In this work the QD model is extended from a pair to a triad of one excited and two ionizable QDs and in total three electrons. Analytical Wigner-Weisskopf expressions for the decay rates are formulated and confirmed with numerical electron dynamics calculations, suggesting a rate enhancement by a factor two that may be relevant for the competitiveness of ICD in QDs. Particularly, we compare two energetic scenarios, one allowing only for single ionization of the QD triad and one, not yet discussed in the community, potentially allowing for double ionization.

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In this work, we investigate the capability of known quantum computing algorithms for fault-tolerant quantum computing to simulate the laser-driven electron dynamics of excitation and ionization processes in small molecules such as lithium hydride, which can be benchmarked against the most accurate time-dependent full configuration interaction (TD-FCI) calculations. The conventional TD-FCI wave packet propagation is reproduced using the Jordan−Wigner transformation for wave function and operators and the Trotter product formula for expressing the propagator. In addition, the time-dependent dipole moment, as an example of a time-dependent expectation value, is calculated using the Hadamard test. To include non-Hermitian operators in the ionization dynamics, a similar approach to the quantum imaginary time evolution (QITE) algorithm is employed to translate the propagator, including a complex absorption potential, into quantum gates. The computations are executed on a quantum computer simulator. By construction, all quantum computer algorithms, except for the QITE algorithm used only for ionization but not for excitation dynamics, would scale polynomially on a quantum computer with fully entangled qubits. In contrast, TD-FCI scales exponentially. Hence, quantum computation holds promises for substantial progress in the understanding of electron dynamics of excitation processes in increasingly large molecular systems, as has already been witnessed in electronic structure theory.

The interparticle Coulombic decay is a synchronized decay and ionization phenomenon occurring on two separated and only Coulomb interaction coupled electron binding sites. This publication explores how drastically small environmental changes in between the two sites, basically impurities, can alter the ionization properties and process rate, although the involved electronic transitions remain unaltered. A comparison among the present electron dynamics calculations for the example of different types of quantum dots, accommodating a one- or a two-dimensional continuum for the outgoing electron, and the well-investigated atomic and molecular cases with three-dimensional continuum, reveals that the impurity effect is most pronounced the stronger that electron is confined. This necessarily leads to challenges and opportunities in a quantum dot experiment to prove the interparticle Coulombic decay.

We introduce a Python 2.7 software called gmx2qmmm, which provides an interface between the Gaussian and Gromacs software packages in an additive quantum mechanics/molecular mechanics (QM/MM) scheme. Other QM packages will be added in future releases. The main advantage of gmx2qmmm is its simplicity in terms of input setup and configuration as it maintains the Gromacs file formats, as well as input conventions. It is also designed such that users do not need to reconfigure or recompile any of the interfaced programs. While our main goal was to provide a simplified transition from Gromacs to QM/MM using Gromacs directly as the basis for the MM part, we considered alternative ways to treat the QM/MM boundary. Our software was also developed to test a previously considered way to account for the presence of link atoms, which we term here link atom correction functions (LCFs). We show that LCFs can be good candidates to improve the forces at the QM/MM junction; however, from our data, it is also apparent that LCFs will not necessarily improve energy barriers, likely due to them being tailored to improve the situation close to potential minima. LCFs are, however, trivial to set up and can be used in the future to support the accuracy of QM/MM optimizations and dynamics. We present data on how our interface compares to a full QM description of small polypeptides; furthermore, we investigate the UV/vis spectroscopy of chlorophyll-containing proteins depending on the employed potentials and geometries.

In a pair of self-assembled or gated laterally-arranged quantum dots, an electronically excited state can undergo interparticle Coulombic decay. Then an electron from a neighbor quantum dot is emitted into the electronic continuum along the two available dimensions.This study proves that the process is not only operative among two, but also among three quantum dots, where a second electron-emitting dot causes a rate increase by a factor of two according to the predictions from the analytical Wigner-Weisskopf rate equation. The predictions hold over the complete range of conformation angles among the quantum dots and over a large range of distances. Electron dynamics was calculated by multiconfiguration time-dependent Hartree and is, irrespective of the large number of discrete variable representation grid points, feasible after having developed an OpenACC graphic card compilation of the program.

Ultrafast electron dynamics has made rapid progress in the last few years. With Jellyfish we now introduce a program suite that enable to perform the entire workflow of an electron-dynamics simulation. The modular program architecture offers the flexible combination of different propagators, Hamiltonians, basis sets and more. Jellyfish can be operated by a graphical user interface, which makes it easy to get started for non-specialist users and gives experienced users a clear overview of entire functionality. The temporal evolution of a wave function can currently be executed in the time-dependent configuration interaction method (TDCI) formalism, however, a plugin system facilitates the expansion to other methods and tools without requiring in-depth knowledge of the program. Currently developed plugins allow to include results from conventional electronic structure calculations as well as the usage and extension of quantum-compute algorithms for electron dynamics. We present the capabilities of Jellyfish on two examples to showcase the simulation and analysis of light-driven correlated electron dynamics. The implemented visualization of various densities enables an efficient and detailed analysis for the long-standing quest of the electron-hole pair formation.

A detailed analysis of the electronic structure and decay dynamics in a symmetric system with three electrons in three linearly aligned binding sites representing quantum dots (QDs) is given. The two outer A QDs are two-level potentials and can act as (virtual) photon emitters, whereas the central B QD can be ionized from its one level into a continuum confined on the QD axis upon absorbing virtual photons in the inter-Coulombic decay (ICD) process. Two scenarios in such an ABA array are explored. One ICD process is from a singly excited resonance state, whose decay releasing one virtual photon we find superimposed with resonance energy transfer among both A QDs. Moreover, the decay-process manifold for a doubly excited (DE) resonance is explored, in which collective ICD among all three sites and excited ICD among the outer QDs engage. Rates for all processes are found to be extremely low, although ICD rates with two neighbors are predicted to double compared to ICD among two sites only. The slowing is caused by Coulomb barriers imposed from ground or excited state electrons in the A sites. Outliers occur on the one hand at short distances, where the charge transfer among QDs mixes the possible decay pathways. On the other hand, we discovered a shape resonance-enhanced DE-ICD pathway, in which an excited and localized B* shape resonance state forms, which is able to decay quickly into the final ICD continuum.