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DY: Fachverband Dynamik und Statistische Physik

DY 35: Poster: Quantum Dynamics and Many-body Systems

DY 35.19: Poster

Wednesday, March 20, 2024, 15:00–18:00, Poster D

Scarred circuits - implementing integer subspaces within digital chaotic quantum dynamics — •Tobias Dörstel and Michael Buchhold — Institut für Theoretische Physik, Universität zu Köln, D-50937 Cologne, Germany

Weak ergodicity breaking describes scenarios where a subpart of the Hilbert space does not thermalise under generic time evolution. In Hamiltonian systems, this corresponds to so-called quantum many-body scar states, which are eigenstates of the Hamiltonian but disobey the eigenstate thermalisation hypothesis. Here, we extend the concept to chaotic quantum circuits by implementing conditioned unitary gates and measurements with feedback. The unitary gates implement the projector-based Shiraishi-Mori construction that leaves the scarred-subspace invariant. Measurements and feedback are designed such that they preserve this subspace and, in addition, guide the dynamics towards the scarred subspace. We study the robustness of the scarred subspace by categorizing the evolution into the scars and their stability against external perturbations. To do so, we combine efficient numerical simulations of so-called conditioned Haar random gates and feedback with analytical arguments.

Keywords: monitored circuit; scar states; weak ergodicity breaking; Haar random; quantum dynamics