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Complex heat capacity as a witness of spatio-temporal entanglement

Mia Stamatova and Vlatko Vedral

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Phys. Rev. A 114, 022448 – Published 24 August, 2026

DOI: https://doi.org/10.1103/vpbk-gcbl

Abstract

We propose a witness of temporal quantum entanglement using the imaginary component of the complex heat capacity—a measurable thermodynamic quantity in temperature-modulated calorimetry. By establishing a direct correspondence between complex heat capacity and the pseudodensity matrix formalism, our approach enables the characterization of both spatial and temporal quantum correlations without demanding additional state-level manipulation beyond initial tomography. We analytically demonstrate this connection for an open quantum system modeled by a qubit coupled to a thermal bath and show how both pseudodensity matrix negativity and violations of a temporal Clauser-Horne-Shimony-Holt inequality emerge as indicators of nonclassical temporal correlations. We further identify bounds on the imaginary heat capacity that guarantee temporal entanglement, providing an experimentally accessible criterion at the macroscopic scale. This framework offers a feasible route for probing temporal quantum effects in condensed-matter systems and opens a viable path toward experimental realization.

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Phys. Rev. A 114, 022448– Published 24 August, 2026
  • Received 2 September 2025
  • Accepted 24 July 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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