Symmetry-protection Zeno phase transition in monitored lattice gauge theories
Year: 2025
Authors: Wauters M.M., Ballini E., Biella A., Hauke P.H.
Autors Affiliation: Univ Trento, BEC Ctr, CNR, INO, Via Sommar 14, I-38123 Trento, Italy; Univ Trento, Dipartimento Fis, Via Sommar 14, I-38123 Trento, Italy; Trento Inst Fundamental Phys & Applicat, INFN, TIFPA, Via Sommar 14, I-38123 Povo, Trento, Italy.
Abstract: Quantum measurements profoundly influence system dynamics. They lead to complex nonequilibrium phenomena like the quantum Zeno effect, and they can be used for mitigating errors in quantum simulations. Such an ability is particularly valuable for lattice gauge theories (LGTs), which require the challenging preservation of an extensive number of local conservation laws. While it is known that tailored quantum measurements can soften violations of gauge symmetry, the nature of this protection, and in particular the possibility of a threshold behavior, is still unexplored. Here, we demonstrate the existence of a sharp transition, triggered by the measurement rate, between a protected gauge-theory regime resistant to simulation errors and an irregular regime. Our results are based on the paradigmatic example of a (1 + 1)-dimensional Z2 LGT. We study in detail the protection through projective measurements of ancillary qubits coupled to the local symmetry generators, and compare this approach with analog (weak) measurement protocols. We show that, while the resulting ensemble averages in the continuous-time limit share the same Liouvillian dynamics, different physical implementations of the stochastic gauge protection protocol yield trajectory unravelings with vastly different statistics. Additionally, we design an on-chip feedback mechanism that corrects bit-flip errors and significantly enhances the discrete-time scheme. Our results shed light on the dissipative criticality of strongly interacting, highly constrained quantum systems, and they offer valuable insights into error mitigation and correction of gauge-theory quantum simulations.
Journal/Review: PHYSICAL REVIEW B
Volume: 111 (9) Pages from: 94315-1 to: 94315-18
More Information: We thank J. Mildenberger, L. Spagnoli, A. Russomanno, and M. Burrello for fruitful discussions. This project has received funding from the European Union’s Horizon Europe research and innovation programme under Grant Agreement No. 101080086 NeQST and from European Union-NextGeneration EU, within PRIN 2022, PNRR M4C2, Project TANQU 2022FLSPAJ [CUP B53D23005130006] . P.H. has further received funding from the Italian Ministry of University and Research (MUR) through the FARE grant for the project DAVNE (Grant R20PEX7Y3A) , from the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number UeMO19-5.1, from the QuantERA II Programme through the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No 101017733, from the European Union under NextGenerationEU, PRIN 2022 Prot. n. 2022ATM8FY (CUP: E53D23002240006) , from the European Union under NextGenerationEU via the ICSC – Centro Nazionale di Ricerca in HPC, Big Data and Quantum Computing. This project has been supported by the Provincia Autonoma di Trento and Q@TN, the joint laboratory between the University of Trento, FBK-Fondazione Bruno Kessler, INFN-National Institute for Nuclear Physics, and CNR- National Research Council. Views and opinions expressed are, however, those of the author (s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the granting authority can be held responsible for them. A.B. would like to thank the Institut Henri Poincare (UAR 839 CNRS-Sorbonne Universite) and the LabEx CARMIN (ANR-10-LABX-59-01) for their support.KeyWords: Quantum Zeno; Python Framework; Dynamics; Invariance; Paradox; QutipDOI: 10.1103/PhysRevB.111.094315
