Universal Quantum Birthmark: Ghost of the quantum past
Ivy Xiaoya, Anton M. Graf, Eric J. Heller, Joonas Keski-Rahkonen

TL;DR
This paper uncovers a universal quantum memory effect called the quantum birthmark, which persists regardless of the system’s chaotic nature, challenging classical ideas of ergodicity and thermalization.
Contribution
It provides a comprehensive theoretical framework for the quantum birthmark, showing it depends only on symmetry class and Hilbert-space dimension, not microscopic details.
Findings
Quantum evolution retains a universal memory of initial conditions.
The quantum birthmark depends solely on symmetry class and Hilbert-space dimension.
This effect questions classical assumptions of ergodicity and thermalization.
Abstract
Quantum dynamics retains a permanent and universal memory of its initial conditions, even in systems whose spectra display fully chaotic, random-matrix behavior. This effect, known as the quantum birthmark, appears as an enhancement of the long-time return probability of any non-stationary state compared to the overlap with a typical ergodic state. In this work, we develop the full theoretical foundation for this universal contribution that depends only on the global symmetry class and accessible Hilbert-space dimension, not on the microscopic dynamics. Our findings reveal that quantum evolution preserves an unavoidable, symmetry-controlled imprint of its origin, a quantum effect calling into question classical expectations of ergodicity and the resulting thermalization scenarios.
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Taxonomy
TopicsQuantum many-body systems · Quantum chaos and dynamical systems · Advanced Thermodynamics and Statistical Mechanics
