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arXiv · 2210.13490

From Dual Unitarity to Generic Quantum Operator Spreading

Michael A. Rampp·Roderich Moessner·Pieter W. Claeys
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Abstract

Dual-unitary circuits are paradigmatic examples of exactly solvable yet chaotic quantum many-body systems, but solvability naturally goes along with a degree of non-generic behaviour. By investigating the effect of weakly broken dual-unitarity on the spreading of local operators we study whether, and how, small deviations from dual-unitarity recover fully generic many-body dynamics. We present a discrete path-integral formula for the out-of-time-order correlator and use it to recover a butterfly velocity smaller than the light-cone velocity, $v_B < v_{LC}$ , and a diffusively broadening operator front, two generic features of ergodic quantum spin chains absent in dual-unitary circuit dynamics. We find that the butterfly velocity and diffusion constant are determined by a small set of microscopic quantities and that the operator entanglement of the gates plays a crucial role.

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Michael A. Rampp, Roderich Moessner, Pieter W. Claeys. 2022-10-24. From Dual Unitarity to Generic Quantum Operator Spreading. https://doi.org/10.1103/physrevlett.130.130402

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