The LCQS welcomed Emiel Koridon from Leiden Universiteit (The Netherlands) during the first week of February 2024. If you want to learn more from Emiel’s work, here is his google scholar link.
He will give a seminar Tuesday, February 6th, 2024 on ‘Quantum Computational Chemistry for the Identification and Description of Conical Intersection Regions ‘.
Abstract:
The recent advances in near-term quantum devices give rise to a need for noise-robust algorithms that minimize device requirements. Working towards this goal from both the chemical as the quantum computational perspective we investigate the identification and description of conical intersections. Conical intersections are topologically protected crossings between the potential energy surfaces of a molecular Hamiltonian and play a pivotal role in chemical processes such as photoisomerization and non-radiative relaxation. They are characterized by a non-zero Berry phase, which is a topological invariant defined on a closed path in atomic coordinate space, taking the value π when the path encircles the intersection manifold. We show that for real molecular Hamiltonians, the Berry phase can be obtained by tracing a local optimum of a variational ansatz along the chosen path and estimating the overlap between the initial and final state with a control-free Hadamard test. Since the Berry phase can only take two discrete values (0 or π), our procedure succeeds even for a cumulative error bounded by a constant; this allows us to bound the total sampling cost and to readily verify the success of the procedure.
