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arXiv:2512.11030 · Physical Review A

Choi echo: dynamical irreversibility and local decoherence in quantum many-body chaos

Jose Alfredo de Leon, Miguel Gonzalez, Carlos Diaz-Mejia

quant-phSubmitted Dec 11, 2025• Announced Dec 15, 2025• 0 citations

v1 · Dec 11, 2025 v2 · Jun 30, 2026

Abstract

Quantifying intrinsic irreversibility in open quantum dynamics is central to understanding decoherence and information loss in many-body systems. In this work, we introduce the Choi echo, which provides an operational interpretation of the purity of the Choi state, the state representation of a quantum channel, as a quantifier of the robustness of quantum correlations against local information erasure. We employ this framework to analyze the reduced dynamics of a subsystem and to test whether local decoherence probes quantum chaos in many-body systems. Across paradigmatic spin chain models, we show that while the Choi echo captures key dynamical features, it also exhibits intrinsic limitations that, in certain regions of parameter space, restrict its ability to resolve the integrable-to-chaos transition at the level of spectral correlations. In particular, we demonstrate that local decoherence can spuriously signal quantum chaos in integrable regimes, tracing them to the inability of a strictly local probe to distinguish efficient coherent transport from genuinely scrambling dynamics. Our results show that local decoherence signals are controlled by the entanglement generated between the probe and its environment during the dynamics, rather than by spectral correlations, clarifying the practical scope of local dynamical diagnostics.

Journal reference: Phys. Rev. A 113, 062224 (2026)
DOI: 10.1103/zdjp-1rck
Comments: 9 pages, 4 figures

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Quantifying intrinsic irreversibility in open quantum dynamics is central to understanding decoherence and information loss in many-body systems. In this work, we introduce the Choi echo, which provides an operational interpretation of the purity of the Choi state, the state representation of a quantum channel, as a quantifier of the robustness of quantum correlations against local information erasure. We employ this framework to analyze the reduced dynamics of a subsystem and to test whether local decoherence probes quantum chaos in many-body systems. Across paradigmatic spin chain models, we show that while the Choi echo captures key dynamical features, it also exhibits intrinsic limitations that, in certain regions of parameter space, restrict its ability to resolve the integrable-to-chaos transition at the level of spectral correlations. In particular, we demonstrate that local decoherence can spuriously signal quantum chaos in integrable regimes, tracing them to the inability of a strictly local probe to distinguish efficient coherent transport from genuinely scrambling dynamics. Our results show that local decoherence signals are controlled by the entanglement generated between the probe and its environment during the dynamics, rather than by spectral correlations, clarifying the practical scope of local dynamical diagnostics.

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We define a quantity, the so-called purity fidelity , which measures the rate of dynamical irreversibility due to decoherence, observed e.g. in echo experiments, in the presence of an arbitrary small perturbation of the total (system + environment) Hamiltonian. We derive a linear response formula for the purity fidelity in terms of integrated time correlation functions of the perturbation. Our relation predicts, similar to the case of fidelity decay, that the faster the decay of purity fidelity the slower is the decay of time correlations. In particular, we find exponential decay in quantum mixing regime and faster, initially quadratic and later typically Gaussian decay in the regime of non-ergodic, e.g. integrable quantum dynamics. We illustrate our approach by an analytical calculation and numerical experiments in the Ising spin 1/2 chain kicked with tilted homogeneous magnetic field where part of the chain is interpreted as a system under observation and part as an environment.

We establish a rigorous connection between quantum coherence and quantum chaos by employing coherence measures originating from the resource theory framework as a diagnostic tool for quantum chaos.We quantify this connection at two different levels: quantum states and quantum channels.At the level of states, we show how several well-studied quantifiers of chaos are, in fact, quantum coherence measures in disguise (or closely related to them).We further this connection for all quantum coherence measures by using tools from majorization theory.Then we numerically study the coherence of chaotic-versus-integrable eigenstates and find excellent agreement with random matrix theory in the bulk of the spectrum.At the level of channels, we show that the coherence-generating power (CGP)-a measure of how much coherence a dynamical process generates on average-emerges as a subpart of the out-of-time-ordered correlator (OTOC), a measure of information scrambling in many-body systems.Via numerical simulations of the (nonintegrable) transverse-field Ising model, we show that the OTOC and CGP capture quantum recurrences in quantitatively the same way.Moreover, using random matrix theory, we analytically characterize the OTOC-CGP connection for the Haar and Gaussian ensembles.In closing, we remark on how our coherence-based signatures of chaos relate to other diagnostics, namely, the Loschmidt echo, OTOC, and the Spectral Form Factor.

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An initial local excitation in a confined quantum system evolves, exploring the whole system and returning to the initial position as a mesoscopic echo at the Heisenberg time. We consider two weakly coupled spin chains, a spin ladder, where one is a quantum channel while the other represents an environment. We quantify decoherence in the quantum channel through the attenuation of the mesoscopic echoes. We evaluate decoherence rates for different ratios between sources of amplitude fluctuation and dephasing in the interchain interaction Hamiltonian. The many-body dynamics is seen as a one-body evolution with a decoherence rate given by the Fermi golden rule.

Decoherence in quantum systems which are classically chaotic is studied. The Arnold cat map and the quantum kicked rotor are chosen as examples of linear and nonlinear chaotic systems. The Feynman-Vernon influence functional formalism is used to study the effect of the environment on the system. It is well known that quantum coherence can obliterate chaotic behavior in the corresponding classical system. But interaction with an environment can under general circumstances quickly diminish quantum coherence and reenact classical chaotic behavior. How effectively decoherence works to sustain chaos, and how the resultant behavior qualitatively differs from the quantum picture, depending on the coupling of the system with the environment and the spectral density and temperature of the environment. We show how recurrence in the quantum cat map is lost and classical ergodicity is recovered due to the effect of the environment. Quantum coherence and diffusion suppression are instrumental to dynamical localization for the kicked rotor. We show how environment-induced effects can destroy this localization. Such effects can also be understood as resulting from external noises driving the system. Peculiar to decohering chaotic systems is the apparent transition from reversible to irreversible dynamics. We show such transitions in the quantum cat map and the kicked rotor and distinguish it from apparent irreversibility originating from dynamical instability and imprecise measurements. By performing a time reversal on and following the quantum kicked rotor dynamics numerically, we show how the otherwise reversible quantum dynamics acquires an arrow of time upon the introduction of noise or interaction with an environment.