SAMOP 2023 – wissenschaftliches Programm
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QI: Fachverband Quanteninformation
QI 6: Poster I (joint session QI/Q)
QI 6.43: Poster
Montag, 6. März 2023, 16:30–19:00, Empore Lichthof
Guided variational quantum algorithm for time evolution in dynamical mean field theory — •Stefan Wolf1, Michael J. Hartmann1, and Martin Eckstein2 — 1Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg — 2I. Institute of Theoretical Physics, Department of Physics, University of Hamburg
Dynamical mean-field theory (DMFT) is a useful tool to treat models of strongly correlated fermions like the Hubbard model. The lattice of the model is replaced by a single-impurity site embedded in an effective bath. The resulting single impurity Anderson model (SIAM) can then be solved self-consistently with a quantum-classical hybrid algorithm. This procedure involves repeatedly preparing the ground state on a quantum computer and evolving it in time. We propose an approximation of the time evolution operator by a Hamiltonian variational ansatz. The parameters of the ansatz are obtained via a variational quantum algorithm that utilizes a small number of Trotter steps, given by the Suzuki-Trotter expansion of the time evolution operator, to guide the evolution of the parameters. The cost function is evaluated by measuring a single ancilla qubit using the Hadamard test, thus reducing the required number of measurements compared to other approaches. The resulting circuit for the time evolution is shallower than a comparable Suzuki-Trotter expansion. We show results for two-site DMFT with half-filling. We further looked into the possibility to extend the approach for the impurity model with more than one bath site and away from half-filling.