Robustness of gauge-invariant dynamics against defects in ultracold-atom gauge theories

Abstract

Recent years have seen strong progress in quantum simulation of gauge-theory dynamics using ultracold-atom experiments. A principal challenge in these efforts is the certification of gauge invariance, which has recently been realized [Yang et al., arXiv:2003.08945]. One major but poorly investigated experimental source of gaugeinvariance violation is an imperfect preparation of the initial state. Using the time-dependent density-matrix renormalization group, we analyze the robustness of gauge-invariant dynamics against potential preparation defects in the above ultracold-atom implementation of a U(1) gauge theory. We find defects related to an erroneous initialization of matter fields to be innocuous, as the associated gauge-invariance violation remains strongly localized throughout the time evolution. A defect due to faulty initialization of the gauge field leads to a mild proliferation of the associated violation. Furthermore, we characterize the influence of immobile and mobile defects by monitoring the spread of entanglement entropy. Overall, our results indicate that the aforementioned experimental realization exhibits a high level of fidelity in the gauge invariance of its dynamics at all evolution times. Our work provides strong evidence that ultracold-atom setups can serve as an extremely reliable framework for the quantum simulation of gauge-theory dynamics.

Suppressing nonperturbative gauge errors in the thermodynamic limit using local pseudogenerators

“…However, recent works have shown that gauge invariance has intrinsic timescales over which it persists, even without protection, in the presence of perturbative errors [54,55]. Furthermore, explicit gauge violations have been shown to remain localized even in large-scale simulators in the presence of linear protection [45,56], performing better than the analytically predicted worstcase scenarios. Therefore, it is natural to ask not only whether LPG protection will fare well in the thermodynamic limit, but also whether it will do so in the presence of nonperturbative errors that can arise in QSM setups [10].…”

“…. , L/2 over which it persists in a staircase of prethermal plateaus in finite systems [55,56]. Eventually, however, the system relaxes into a steady state of maximal gauge violation if no gauge protection is employed [25].…”

Observation of unconventional many-body scarring in a quantum simulator

“…Notably, this protocol can be used to probe the global fidelity, as well as the out-of-time correlations between arbitrary quantum states, e.g., |⟨ψ(t 1 )| |ψ(t 2 )⟩| 2 , with the help of single-atom resolution quantum gas microscopes [43,45]. This would empower detailed experimental studies of exotic quantum phenomena such as dynamical quantum phase transitions [46]. The observation of long-lived quantum coherence due to scarring and its controllable enhancement via periodic modulation, lays the foundation for applications such as quantum memories and quantum sensing [47].…”

From quantum link models to D-theory: a resource efficient framework for the quantum simulation and computation of gauge theories

“…Most remarkably, quantum simulation experiments of quantum link models including matter fields using ultracold atomic gases in optical superlattices have already been performed successfully [41,42], with impressive control of the gauge symmetry. Numerous different aspects of (2 + 1)-d U(1) quantum link models have been investigated in [52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68].…”