| 1. |
- Fitzek, David, 1993, et al.
(författare)
-
Optimizing Variational Quantum Algorithms with qBang: Efficiently Interweaving Metric and Momentum to Navigate Flat Energy Landscapes
- 2024
-
Ingår i: Quantum. - 2521-327X. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- Variational quantum algorithms (VQAs) represent a promising approach to utilizing current quantum computing infrastructures. VQAs are based on a parameterized quantum circuit optimized in a closed loop via a classical algorithm. This hybrid approach reduces the quantum processing unit load but comes at the cost of a classical optimization that can feature a flat energy landscape. Existing optimization techniques, including either imaginary time -propagation, natural gradient, or momentum -based approaches, are promising candidates but place either a significant burden on the quantum device or suffer frequently from slow convergence. In this work, we propose the quantum Broyden adaptive natural gradient (qBang) approach, a novel optimizer that aims to distill the best aspects of existing approaches. By employing the Broyden approach to approximate updates in the Fisher information matrix and combining it with a momentumbased algorithm, qBang reduces quantumresource requirements while performing better than more resource -demanding alternatives. Benchmarks for the barren plateau, quantum chemistry, and the maxcut problem demonstrate an overall stable performance with a clear improvement over existing techniques in the case of flat (but not exponentially flat) optimization landscapes. qBang introduces a new development strategy for gradient -based VQAs with a plethora of possible improvements.
|
|
| 2. |
- Baranov, Denis G., et al.
(författare)
-
Toward Molecular Chiral Polaritons
- 2023
-
Ingår i: ACS Photonics. - 2330-4022. ; 10:8, s. 2440-2455
-
Tidskriftsartikel (refereegranskat)abstract
- Coupling between light and material excitations underliesa widerange of optical phenomena. Polaritons are eigenstates of a coupledsystem with a hybridized wave function. Owing to their hybrid composition,polaritons exhibit at the same time properties typical for photonicand electronic excitations, thus offering new ways for controllingelectronic transport and even chemical kinetics. While most theoreticaland experimental efforts have been focused on polaritons with electric-dipolecoupling between light and matter, in chiral quantum emitters, electronictransitions are characterized by simultaneously nonzero electric andmagnetic dipole moments. Thus, it is natural to wonder what kindsof novel effects chirality may enable in the realm of strong light-mattercoupling. Right now, this field located at the intersection of nanophotonics,quantum optics, and chemistry is in its infancy. In this Perspective,we offer our view toward chiral polaritons. We review basic physicalconcepts underlying chirality of matter and electromagnetic field,discuss the main theoretical and experimental challenges that needto be solved, and consider novel effects that could be enabled bystrong coupling between chiral light and matter.
|
|
| 3. |
- Castagnola, Matteo, et al.
(författare)
-
Collective Strong Coupling Modifies Aggregation and Solvation
- 2024
-
Ingår i: Journal of Physical Chemistry Letters. - 1948-7185. ; 15, s. 1428-1434
-
Tidskriftsartikel (refereegranskat)abstract
- Intermolecular (Coulombic) interactions are pivotal for aggregation, solvation, and crystallization. We demonstrate that the collective strong coupling of several molecules to a single optical mode results in notable changes in the molecular excitations around a single perturbed molecule, thus representing an impurity in an otherwise ordered system. A competition between short-range coulombic and long-range photonic correlations inverts the local transition density in a polaritonic state, suggesting notable changes in the polarizability of the solvation shell. Our results provide an alternative perspective on recent work in polaritonic chemistry and pave the way for the rigorous treatment of cooperative effects in aggregation, solvation, and crystallization.
|
|
| 4. |
- Mortensen, Jens Jorgen, et al.
(författare)
-
GPAW: An open Python package for electronic structure calculations
- 2024
-
Ingår i: Journal of Chemical Physics. - 1089-7690 .- 0021-9606. ; 160:9
-
Tidskriftsartikel (refereegranskat)abstract
- We review the GPAW open-source Python package for electronic structure calculations. GPAW is based on the projector-augmented wave method and can solve the self-consistent density functional theory (DFT) equations using three different wave-function representations, namely real-space grids, plane waves, and numerical atomic orbitals. The three representations are complementary and mutually independent and can be connected by transformations via the real-space grid. This multi-basis feature renders GPAW highly versatile and unique among similar codes. By virtue of its modular structure, the GPAW code constitutes an ideal platform for the implementation of new features and methodologies. Moreover, it is well integrated with the Atomic Simulation Environment (ASE), providing a flexible and dynamic user interface. In addition to ground-state DFT calculations, GPAW supports many-body GW band structures, optical excitations from the Bethe-Salpeter Equation, variational calculations of excited states in molecules and solids via direct optimization, and real-time propagation of the Kohn-Sham equations within time-dependent DFT. A range of more advanced methods to describe magnetic excitations and non-collinear magnetism in solids are also now available. In addition, GPAW can calculate non-linear optical tensors of solids, charged crystal point defects, and much more. Recently, support for graphics processing unit (GPU) acceleration has been achieved with minor modifications to the GPAW code thanks to the CuPy library. We end the review with an outlook, describing some future plans for GPAW.
|
|
| 5. |
- Schäfer, Christian, 1989, et al.
(författare)
-
Chiral Polaritonics: Analytical Solutions, Intuition, and Use
- 2023
-
Ingår i: Journal of Physical Chemistry Letters. - 1948-7185. ; 14:15, s. 3777-3784
-
Tidskriftsartikel (refereegranskat)abstract
- Preferential selection of a given enantiomer over its chiral counterpart has become increasingly relevant in the advent of the next era of medical drug design. In parallel, cavity quantum electrodynamics has grown into a solid framework to control energy transfer and chemical reactivity, the latter requiring strong coupling. In this work, we derive an analytical solution to a system of many chiral emitters interacting with a chiral cavity similar to the widely used Tavis-Cummings and Hopfield models of quantum optics. We are able to estimate the discriminating strength of chiral polaritonics, discuss possible future development directions and exciting applications such as elucidating homochirality, and deliver much needed intuition to foster the newly flourishing field of chiral polaritonics.
|
|
| 6. |
- Schäfer, Christian, 1989, et al.
(författare)
-
Machine Learning for Polaritonic Chemistry: Accessing Chemical Kinetics
- 2024
-
Ingår i: Journal of the American Chemical Society. - 1520-5126 .- 0002-7863. ; 146:8, s. 5402-5413
-
Tidskriftsartikel (refereegranskat)abstract
- Altering chemical reactivity and material structure in confined optical environments is on the rise, and yet, a conclusive understanding of the microscopic mechanisms remains elusive. This originates mostly from the fact that accurately predicting vibrational and reactive dynamics for soluted ensembles of realistic molecules is no small endeavor, and adding (collective) strong light-matter interaction does not simplify matters. Here, we establish a framework based on a combination of machine learning (ML) models, trained using density-functional theory calculations and molecular dynamics to accelerate such simulations. We then apply this approach to evaluate strong coupling, changes in reaction rate constant, and their influence on enthalpy and entropy for the deprotection reaction of 1-phenyl-2-trimethylsilylacetylene, which has been studied previously both experimentally and using ab initio simulations. While we find qualitative agreement with critical experimental observations, especially with regard to the changes in kinetics, we also find differences in comparison with previous theoretical predictions. The features for which the ML-accelerated and ab initio simulations agree show the experimentally estimated kinetic behavior. Conflicting features indicate that a contribution of dynamic electronic polarization to the reaction process is more relevant than currently believed. Our work demonstrates the practical use of ML for polaritonic chemistry, discusses limitations of common approximations, and paves the way for a more holistic description of polaritonic chemistry.
|
|
| 7. |
- Schäfer, Christian, 1989, et al.
(författare)
-
Making ab initio QED functional(s): Nonperturbative and photon-free effective frameworks for strong light-matter coupling
- 2021
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 118:41
-
Tidskriftsartikel (refereegranskat)abstract
- Strong light-matter coupling provides a promising path for the control of quantum matter where the latter is routinely described from first principles. However, combining the quantized nature of light with this ab initio tool set is challenging and merely developing as the coupled light-matter Hilbert space is conceptually different and computational cost quickly becomes overwhelming. In this work, we provide a nonperturbative photon-free formulation of quantum electrodynamics (QED) in the long-wavelength limit, which is formulated solely on the matter Hilbert space and can serve as an accurate starting point for such ab initio methods. The present formulation is an extension of quantum mechanics that recovers the exact results of QED for the zero and infinite-coupling limit and the infinite-frequency as well as the homogeneous limit, and we can constructively increase its accuracy. We show how this formulation can be used to devise approximations for quantum-electrodynamical density-functional theory (QEDFT), which in turn also allows us to extend the ansatz to the full minimal-coupling problem and to nonadiabatic situations. Finally, we provide a simple local density-type functional that takes the strong coupling to the transverse photon degrees of freedom into account and includes the correct frequency and polarization dependence. This QEDFT functional accounts for the quantized nature of light while remaining computationally simple enough to allow its application to a large range of systems. All approximations allow the seamless application to periodic systems.
|
|
| 8. |
- Schäfer, Christian, 1989
(författare)
-
Polaritonic Chemistry from First Principles via Embedding Radiation Reaction
- 2022
-
Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 13:30, s. 6905-6911
-
Tidskriftsartikel (refereegranskat)abstract
- The coherent interaction of a large collection of molecules with a common photonic mode results in strong light-matter coupling, a feature that has proven highly beneficial for chemistry and has introduced the research topics polaritonic and QED chemistry. Here, we demonstrate an embedding approach to capture the collective nature while retaining the full ab initio representation of single molecules─an approach ideal for polaritonic chemistry. The accuracy of the embedding radiation-reaction ansatz is demonstrated for time-dependent density-functional theory. Then, by virtue of a simple proton-tunneling model, we illustrate that the influence of collective strong coupling on chemical reactions features a nontrivial dependence on the number of emitters and can alternate between strong catalyzing and an inhibiting effect. Bridging classical electrodynamics, quantum optical descriptions, and the ab initio description of realistic molecules, this work can serve as a guiding light for future developments and investigations in the quickly growing fields of QED chemistry and QED material design.
|
|
| 9. |
- Schäfer, Christian, 1989, et al.
(författare)
-
Shining light on the microscopic resonant mechanism responsible for cavity-mediated chemical reactivity
- 2022
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 13:1
-
Tidskriftsartikel (refereegranskat)abstract
- Strong light–matter interaction in cavity environments is emerging as a promising approach to control chemical reactions in a non-intrusive and efficient manner. The underlying mechanism that distinguishes between steering, accelerating, or decelerating a chemical reaction has, however, remained unclear, hampering progress in this frontier area of research. We leverage quantum-electrodynamical density-functional theory to unveil the microscopic mechanism behind the experimentally observed reduced reaction rate under cavity induced resonant vibrational strong light-matter coupling. We observe multiple resonances and obtain the thus far theoretically elusive but experimentally critical resonant feature for a single strongly coupled molecule undergoing the reaction. While we describe only a single mode and do not explicitly account for collective coupling or intermolecular interactions, the qualitative agreement with experimental measurements suggests that our conclusions can be largely abstracted towards the experimental realization. Specifically, we find that the cavity mode acts as mediator between different vibrational modes. In effect, vibrational energy localized in single bonds that are critical for the reaction is redistributed differently which ultimately inhibits the reaction.
|
|
| 10. |
- Schäfer, Christian, 1989, et al.
(författare)
-
Shortcut to Self-Consistent Light-Matter Interaction and Realistic Spectra from First Principles
- 2022
-
Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 128:15
-
Tidskriftsartikel (refereegranskat)abstract
- We introduce a simple approach to how an electromagnetic environment can be efficiently embedded into state-of-the-art electronic structure methods, taking the form of radiation-reaction forces. We demonstrate that this self-consistently provides access to radiative emission, natural linewidth, Lamb shifts, strong coupling, electromagnetically induced transparency, Purcell-enhanced and superradiant emission. As an example, we illustrate its seamless integration into time-dependent density-functional theory with virtually no additional cost, presenting a convenient shortcut to light-matter interactions.
|
|
| 11. |
- Shin, Dongbin, et al.
(författare)
-
Simulating Terahertz Field-Induced Ferroelectricity in Quantum Paraelectric SrTiO3
- 2022
-
Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 129:16
-
Tidskriftsartikel (refereegranskat)abstract
- Recent experiments have demonstrated that light can induce a transition from the quantum paraelectric to the ferroelectric phase of SrTiO3. Here, we investigate this terahertz field-induced ferroelectric phase transition by solving the time-dependent lattice Schrödinger equation based on first-principles calculations. We find that ferroelectricity originates from a light-induced mixing between ground and first excited lattice states in the quantum paraelectric phase. In agreement with the experimental findings, our study shows that the nonoscillatory second harmonic generation signal can be evidence of ferroelectricity in SrTiO3. We reveal the microscopic details of this exotic phase transition and highlight that this phenomenon is a unique behavior of the quantum paraelectric phase.
|
|
| 12. |
- Sidler, Dominik, et al.
(författare)
-
A perspective on ab initio modeling of polaritonic chemistry: The role of non-equilibrium effects and quantum collectivity
- 2022
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 156:23
-
Tidskriftsartikel (refereegranskat)abstract
- This Perspective provides a brief introduction into the theoretical complexity of polaritonic chemistry, which emerges from the hybrid nature of strongly coupled light-matter states. To tackle this complexity, the importance of ab initio methods is highlighted. Based on those, novel ideas and research avenues are developed with respect to quantum collectivity, as well as for resonance phenomena immanent in reaction rates under vibrational strong coupling. Indeed, fundamental theoretical questions arise about the mesoscopic scale of quantum-collectively coupled molecules when considering the depolarization shift in the interpretation of experimental data. Furthermore, to rationalize recent findings based on quantum electrodynamical density-functional theory (QEDFT), a simple, but computationally efficient, Langevin framework is proposed based on well-established methods from molecular dynamics. It suggests the emergence of cavity-induced non-equilibrium nuclear dynamics, where thermal (stochastic) resonance phenomena could emerge in the absence of external periodic driving. Overall, we believe that the latest ab initio results indeed suggest a paradigmatic shift for ground-state chemical reactions under vibrational strong coupling from the collective quantum interpretation toward a more local, (semi)-classically and non-equilibrium dominated perspective. Finally, various extensions toward a refined description of cavity-modified chemistry are introduced in the context of QEDFT, and future directions of the field are sketched.
|
|
| 13. |
- Xu, Nan, et al.
(författare)
-
Tensorial Properties via the Neuroevolution Potential Framework: Fast Simulation of Infrared and Raman Spectra
- 2024
-
Ingår i: Journal of Chemical Theory and Computation. - 1549-9626 .- 1549-9618. ; 20:8, s. 3273-3284
-
Tidskriftsartikel (refereegranskat)abstract
- Infrared and Raman spectroscopy are widely used for the characterization of gases, liquids, and solids, as the spectra contain a wealth of information concerning, in particular, the dynamics of these systems. Atomic scale simulations can be used to predict such spectra but are often severely limited due to high computational cost or the need for strong approximations that limit the application range and reliability. Here, we introduce a machine learning (ML) accelerated approach that addresses these shortcomings and provides a significant performance boost in terms of data and computational efficiency compared with earlier ML schemes. To this end, we generalize the neuroevolution potential approach to enable the prediction of rank one and two tensors to obtain the tensorial neuroevolution potential (TNEP) scheme. We apply the resulting framework to construct models for the dipole moment, polarizability, and susceptibility of molecules, liquids, and solids and show that our approach compares favorably with several ML models from the literature with respect to accuracy and computational efficiency. Finally, we demonstrate the application of the TNEP approach to the prediction of infrared and Raman spectra of liquid water, a molecule (PTAF-), and a prototypical perovskite with strong anharmonicity (BaZrO3). The TNEP approach is implemented in the free and open source software package gpumd, which makes this methodology readily available to the scientific community.
|
|
