QuICS Special Seminar: Shachar Fraenkel

Title:  Entanglement in dual-unitary quantum circuits with impurities
Speaker:  Shachar Fraenkel (Tel Aviv University)
Date & Time:  February 5, 2025, 11:00am
Where to Attend:  ATL 3100A and Virtual Via Zoom: https://umd.zoom.us/j/93193341356?pwd=eP1zjLaqybtvE4n9ozwR3cfxqZVbEb.1 Meeting ID: 931 9334 1356 Passcode: 760966

Universal behaviors of nonequilibrium quantum many-body systems may be usefully captured by the dynamics of quantum information measures. Notably, the dynamics of bipartite entanglement entropy can distinguish integrable quantum systems from chaotic ones. The two most successful effective theories describing the evolution of entanglement from a low-entangled initial state are the quasiparticle picture and the membrane picture, which provide distinct predictions for integrable and chaotic systems, respectively.

I will present exact results for entanglement dynamics in integrable and chaotic systems perturbed by a quantum impurity, showing that the impurity’s presence strongly alters the growth of entanglement. Specifically, this question is studied in dual-unitary quantum circuits perturbed by impurities, where the dual-unitarity of the bulk is leveraged to facilitate analytical calculations. I will show that in the case of the integrable bulk, a modified version of the integrable quasiparticle picture still holds, despite the impurity generically breaking integrability. On the other hand, the analytical results indicate that for certain chaotic bulk systems, entanglement dynamics are at odds with the simple membrane picture, raising the need for a more fine-grained theory. I will conclude by making contact with results concerning long-range entanglement mediated by impurities in noninteracting continuous-time lattice models, highlighting the prospect of using quantum circuit models to generalize the scope of this phenomenon.

Based on: S. Fraenkel and C. Rylands, Entanglement in dual unitary quantum circuits with impurities, arXiv:2410.03442 (2024).

 *We strongly encourage attendees to use their full name (and if possible, their UMD credentials) to join the zoom session.*