Universal Quantum Birthmark: Ghost of the quantum past
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.
Cite
@article{arxiv.2602.00891,
title = {Universal Quantum Birthmark: Ghost of the quantum past},
author = {Ivy Xiaoya and Anton M. Graf and Eric J. Heller and Joonas Keski-Rahkonen},
journal= {arXiv preprint arXiv:2602.00891},
year = {2026}
}