Quantum Quenches that Resemble Operator Growth

• URL: http://arxiv.org/abs/2605.23874v2
• Date: Tue, 26 May 2026 07:33:31 GMT
• Title: Quantum Quenches that Resemble Operator Growth
• Abstract summary: We study growth quenches, which may gradually destabilize a false vacuum in certain kinetic constrained quantum lattice models.<n>We show that the growth quench dynamics is localized in both Krylov and Fock spaces.<n>In the 1D East-West model, we interpret Fock space cage states as the existence of a conserved charge.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: We study growth quenches, which are local quenches that may gradually destabilize a false vacuum in certain kinetic constrained quantum lattice models, such as the East-West model. We point out a formal analogy with the dynamics of a local operator in the Heisenberg picture. Exploiting this analogy, we obtain several results on growth quenches by adapting operator-dynamics concepts and methods. First, applying the Krylov approach (recursion method), we conjecture the linear growth of Lanzcos coefficients in generic quenches, $a_m \sim νm$ (diagonal), and $b_m \sim αm$ (off-diagonal), extending an operator growth hypothesis. We show that the growth quench dynamics is localized in both Krylov and Fock spaces when $|ν| > 2 α$, and derive a bound for the growth quench analogue of Lyapunov exponent $λ_L \le \sqrt{4 α^2 - ν^2}$ when $|ν| < 2 α$. Second, we realize the Fock localization in large $N$ solvable growth quenches inspired by Sachdev-Ye-Kitaev (SYK) models. The bound on Lyapunov exponent is saturated in large-$q$ SYK grow quench. By contrast, the growth quench is almost always Fock localized in a nonrandom all-to-all growth quench amenable to semiclassics. Finally, in the 1D East-West model, we interpret Fock space cage states as the existence of a conserved charge. We show that the latter has ballistic transport due to current conservation. Moreover, adding hopping with a fine-tuned amplitude induces a partial localization due to a flat band. Our work suggest growth quenches as a promising approach to realize non-equilibrium coherent phenomena in many-body systems.

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