We propose to use quantum information notions to characterize thermally induced melting of nonperturbative bound states at high temperatures. We apply tensor networks to investigate this idea in static and dynamical settings within the Ising quantum field theory, where bound states are confined fermion pairs—mesons. An equilibrium signature of meson melting is identified in the temperature dependence of the thermal-state second Rényi entropy, which varies from exponential to power-law scaling. Out of equilibrium, we identify as the relevant signature the transition from an oscillatory to a linear growing behavior of reflected entropy after a thermal quench. These analyses apply more broadly, which brings new ways of describing in-medium meson phenomena in quantum many-body and high-energy physics.

• Received 4 October 2022
• Revised 28 May 2023
• Accepted 21 September 2023

DOI:https://doi.org/10.1103/PhysRevD.108.076016

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Published by the American Physical Society