A hybrid quantum algorithm to detect conical intersections

by Joanna Fraxanet Morales (ICFO-The Institute of Photonic Sciences)

Friday 21 Jul 2023, 14:00 → 15:00 Europe/Berlin

Seminar Room 5

Conical intersections are topologically protected crossings between the potential energy surfaces of a molecular Hamiltonian, known to play an important role in certain chemical processes. Characterizing their properties poses challenges for current available methods, but their presence can be resolved 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.

 

In quantum chemistry, variational quantum algorithms are often proposed as a method to resolve ground state energies to high accuracy, demanding a number of samples and convergence requirements which are often out of reach. For this reason, it is compelling to suggest alternative quantities that are less reliant on the precision of both the optimization process and the measurement procedure.

 

In this talk, I will present a hybrid quantum algorithm to compute the Berry phase, which can be obtained by tracing a local optimum of a variational ansatz along a chosen path and estimating the overlap between the initial and final state with a control-free Hadamard test. In particular, since the Berry phase can only take two discrete values, our procedure succeeds even for a cumulative error bounded by a constant.

 

https://desy.zoom.us/j/66566624655?pwd=eWJTR1BndzhZMnVGWjNpRm9sTmxqQT09

Meeting-ID: 665 6662 4655
Code: 798733