Izmaylov Research Group
Izmaylov Research Group
Research
The main efforts of our group are directed toward developing electronic structure and quantum dynamics methods on classical and quantum computers to obtain detailed understanding of processes involving simultaneous changes in electronic and nuclear states. Such processes constitute crucial steps in many areas of fundamental and technological importance: solar energy conversion, UV-light DNA damage and repair, operation of MRI contrast agents, catalysis at surfaces, and general surface chemistry.
Overview
Ongoing projects
Representative publications:
1)I. G. Ryabinkin and A. F. Izmaylov, Geometric phase effects in dynamics near conical intersections: Symmetry breaking and spatial localization, Phys. Rev. Lett., 111, 220406 (2013)
2)I. G. Ryabinkin, L. Joubert-Doriol, and A. F. Izmaylov When do we need to account for the geometric phase in excited state dynamics? J. Chem. Phys. 140, 214116 (2014)
3)R. Gherib, I. G. Ryabinkin, and A. F. Izmaylov Why do mixed quantum-classical methods describe short-time dynamics through conical intersections so well? Analysis of geometric phase effects, J. Chem. Theory Comp., 11, 1375 (2015)
4)A. F. Izmaylov, J. Li, and L. Joubert-Doriol, Diabatic definition of geometric phase effects, J. Chem. Theory Comp. 12, 5278 (2016)
5)L. Joubert-Doriol, J. Sivasubramanium, I. G. Ryabinkin, and A. F. Izmaylov, Topologically correct quantum nonadiabatic formalism for on-the-fly dynamics, J. Phys. Chem. Lett. 8, 452 (2017)
YouTube videos:
2. Geometric phase effects in nonadiabatic dynamics
3. Method development for energy and charge transfer in organic molecules
Representative publications:
1)A. F. Izmaylov, Perturbative Wave-packet Spawning Procedure for Non-adiabatic Dynamics in Diabatic Representation, J. Chem. Phys., 138, 104115 (2013)
2)L. Joubert-Doriol, I. G. Ryabinkin, and A. F. Izmaylov Non-stochastic matrix Schrödinger equation for open systems, J. Chem. Phys. 141, 234112 (2014)
3)J. Nagesh, A. F. Izmaylov, and P. Brumer An efficient implementation of the localized operator partitioning method for electronic energy transfer, J. Chem. Phys. 142, 084114 (2015)
4)J. Nagesh, M. J. Frisch, P. Brumer, and A. F. Izmaylov, Localized operator partitioning method for electronic excitation energies in the time-dependent density functional formalism, J. Chem. Phys. 145, 244111 (2016)
5)A. F. Izmaylov and L. Joubert-Doriol, Quantum Nonadiabatic Cloning of Entangled Coherent States, J. Phys. Chem. Lett. 8, 1793 (2017)
Representative publications:
1)A. Klinkova, P.V. Cherepanov, I. G. Ryabinkin, M. Ho, M. Ashokkumar, A. F. Izmaylov, D. V. Andreeva, E. Kumacheva, Shape-dependent Interactions of Palladium Nanocrystals with Hydrogen, Small, 12, 2450 (2016)
2)I. G. Ryabinkin and A. F. Izmaylov, Mixed quantum-classical dynamics using collective electronic variables: A better alternative to electronic friction theories, J. Phys. Chem. Lett. 8, 440 (2017)
4. Modeling Chemical Reactions on Metallic Surfaces and Nanostructures
1. Quantum computing
The electronic structure problem is at the heart of our understanding of atomic and molecular electronic properties, which are so crucial for the rational molecular and material designs. Unfortunately, the computational cost of the electronic structure problem scales exponentially with the system size and presents a great challenge for a classical computer. On the other hand, there is a hope to overcome the exponential scaling by engaging a quantum computer. One of the main practical difficulties remains maintaining large enough number of qubits in a coherent superposition state entangling several particles. Another issue is related to reformulating the electronic structure problem for the quantum computer.
Recently, the Variational Quantum Eigensolver (VQE) method was developed to solve the electronic structure problem on a quantum computer. However, VQE is insufficient for accessing any molecular state but the ground state of an ionic form with the lowest electronic energy. For example, in the case of the H2 molecule, a potential energy surface of H2+ cannot be obtained (even though it is the simplest molecular problem with a single electron), because the cation is higher in energy than the neutral form. In our work, we fully resolve this embarrassing problem by proposing a methodology for constrained search [1]. The constrained search adds restrictions on the number of electrons and their spin in the state of interest.
We demonstrate the capacity of our constrained VQE (cVQE) methodology by simulating ground states of the H2 molecule and its cation with 4 qubits on the 19Q-Acorn quantum processor. Our method features a low gate count with total number of gates linearly proportional to the number of qubits used. This enables us to treat even larger molecules, such as H2O (8 qubits and close to 200 non-commuting Pauli terms in the Hamiltonian)[1].
Representative publications:
1) I. G. Ryabinkin, S. N. Genin, A. F. Izmaylov, Constrained variational quantum eigensolver: Quantum computer search engine in the Fock space, arXiv:1806.00461
2) I. G. Ryabinkin, S. N. Genin, A. F. Izmaylov, Relation between fermionic and qubit mean fields in the electronic structure problem, arXiv:1806.00514