Simulation of dissipative quantum dynamics through an engineered conical intersection

Conical intersections (CIs) are ubiquitous features in quantum chemistry where two molecular potential energy surfaces intersect. Characterized by a breakdown of the Born-Oppenheimer approximation, they result in strong hybridization between electronic and nuclear motion. CIs enable nonadiabatic transitions between electronic states and may heavily influence outcomes of chemical reactions via wave packet branching. Engineering synthetic CIs with tunable control to systematically explore the parameter space is a promising application of quantum simulators. In this talk, we report experimental results on controlling and measuring wave packet dynamics through an engineered CI in a superconducting circuit with one nonlinear (electronic) and two linear (nuclear, one reactive and one bath) modes. We characterize the measurement induced dephasing of the qubit via the bath mode, which drives wave packet branching in our model, and demonstrate the influence of excited state dynamics of the reactive mode on the effective dephasing rate in the presence of the CI. Specifically, we show that the dephasing, and hence the branching ratio, is influenced via a competition between the noise from the bath and the reorganization energy of the reactive coordinate.