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Pré-Publication, Document De Travail (Preprint/Prepublication) Année : 2022

Integrable Digital Quantum Simulation: Generalized Gibbs Ensembles and Trotter Transitions

Résumé

The Trotter-Suzuki decomposition is a promising avenue for digital quantum simulation (DQS), approximating continuous-time dynamics by discrete Trotter steps of duration τ. Recent work suggested that DQS is typically characterized by a sharp Trotter transition: when τ is increased beyond a threshold value, approximation errors become uncontrolled at large times due to the onset of quantum chaos. Here we contrast this picture with the case of integrable DQS. We focus on a simple quench from a spin-wave state in the prototypical XXZ Heisenberg spin chain, and study its integrable Trotterized evolution as a function of τ. Due to its exact local conservation laws, the system does not heat up to infinite temperature and the late-time properties of the dynamics are captured by a discrete Generalized Gibbs Ensemble (dGGE). By means of exact calculations we find that, for small τ , the dGGE depends analytically on the Trotter step, implying that discretization errors remain bounded even at infinite times. Conversely, the dGGE changes abruptly at a threshold value τ th , signaling a novel type of Trotter transition. We show that the latter can be detected locally, as it is associated with the appearance of a non-zero staggered magnetization with a subtle dependence on τ. We highlight the differences between continuous and discrete GGEs, suggesting the latter as novel interesting nonequilibrium states exclusive to digital platforms.
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hal-03897619 , version 1 (14-12-2022)

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Eric Vernier, Bruno Bertini, Giuliano Giudici, Lorenzo Piroli. Integrable Digital Quantum Simulation: Generalized Gibbs Ensembles and Trotter Transitions. 2022. ⟨hal-03897619⟩
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