Publications Gabriele CALLIARI

2025

Article

• G. Calliari, M. Di Liberto, H. Pichler, T. Zache Quantum simulating continuum field theories with large-spin lattice models, PRX Quantum 6 30304 (2025-07-09), http://dx.doi.org/10.1103/nt76-ttmj doi:10.1103/nt76-ttmj (ID: 721390) Toggle Abstract
  Simulating the real-time dynamics of quantum field theories (QFTs) is one of the most promising applications of quantum simulators. Regularizing a bosonic QFT for quantum simulation purposes typically involves a truncation in Hilbert space in addition to a discretization of space. Here, we discuss how to perform such a regularization of scalar QFTs using multi-level or qudit systems, and show that this enables quantitative predictions in the continuum limit by extrapolating results obtained for large-spin lattice models. With extensive matrix-product state simulations, we numerically demonstrate the sequence of extrapolations that leads to quantitative agreement of observables for the integrable sine-Gordon (sG) QFT. We further show how to prepare static and moving soliton excitations, and analyze their scattering dynamics, in agreement with a semi-classical model and analytical predictions. Finally, we illustrate how a non-integrable perturbation of the sG model gives rise to dynamics reminiscent of string breaking and plasma oscillations in gauge theories. Our methods are directly applicable in state-of-the-art analog quantum simulators, opening the door to implementing a wide variety of scalar field theories and tackling long-standing questions in non-equilibrium QFT like the fate of the false vacuum.

Preprints

• L. Bombieri, T. Zache, G. Calliari, M. Lukin, H. Pichler, D. Gonzalez Cuadra Deconfined quantum criticality on a triangular Rydberg array, (2025-08-11), arXiv:2508.08366 arXiv:2508.08366 (ID: 721492) Toggle Abstract
  Fluctuations can drive continuous phase transitions between two distinct ordered phases -- so-called Deconfined Quantum Critical points (DQCPs) -- which lie beyond the Landau-Ginzburg-Wilson paradigm. Despite several theoretical predictions over the past decades, experimental evidence of DQCPs remains elusive. We show that a DQCP can be explored in a system of Rydberg atoms arranged on a triangular lattice and coupled through van der Waals interactions. Specifically, we investigate the nature of the phase transition between two ordered phases at 1/3 and at 2/3 Rydberg excitation density, which were recently probed experimentally in [P. Scholl et al., Nature 595, 233 (2021)]. Using a field-theoretical analysis, we predict both the critical exponents for infinitely long cylinders of increasing circumference and the emergence of a conformal field theory near criticality showing an enlarged U(1) symmetry -- a signature of DQCPs -- and confirm these predictions numerically. Finally, we extend these results to ladder geometries and show how the emergent U(1) symmetry could be probed experimentally using finite tweezer arrays.
• G. Calliari, R. Ott, H. Pichler, T. Zache Field digitization scaling in a Z symmetric model, (2025-07-30), arXiv:2507.22984 arXiv:2507.22984 (ID: 721491) Toggle Abstract
  The simulation of quantum field theories, both classical and quantum, requires regularization of infinitely many degrees of freedom. However, in the context of field digitization (FD) -- a truncation of the local fields to discrete values -- a comprehensive framework to obtain continuum results is currently missing. Here, we propose to analyze FD by interpreting the parameter as a coupling in the renormalization group (RG) sense. As a first example, we investigate the two-dimensional classical -state clock model as a Z FD of the -symmetric -model. Using effective field theory, we employ the RG to derive generalized scaling hypotheses involving the FD parameter , which allows us to relate data obtained for different -regularized models in a procedure that we term (FDS). Using numerical tensor-network calculations at finite bond dimension , we further uncover an unconventional universal crossover around a low-temperature phase transition induced by finite , demonstrating that FDS can be extended to describe the interplay of and . Finally, we analytically prove that our calculations for the 2D classical-statistical Z clock model are directly related to the quantum physics in the ground state of a (2+1)D Z lattice gauge theory which serves as a FD of compact quantum electrodynamics. Our study thus paves the way for applications of FDS to quantum simulations of more complex models in higher spatial dimensions, where it could serve as a tool to analyze the continuum limit of digitized quantum field theories.