Quantum

Finite Measured Entropy Production Does Not Imply Finite Microscopic Irreversibility

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Based on a feed excerpt; full article content has not been acquired. Source evidence retrieved 11/11/2026, 05:13:25 UTC.

Briefings

A driven quantum system with an imperfect counter register exhibits a finite, positive arrow of time despite having infinite microscopic entropy production. This occurs in a degenerate parametric oscillator below threshold, coupled to a thermal reservoir via bosonic ancillas. The system sustains a finite heat current into the vacuum bath where absorption is forbidden, creating a support mismatch between trajectory laws. A photon counter with finite collection efficiency and independent dark counts provides a coarse-grained measurement that remains uniformly bounded as temperature vanishes, while the hidden contribution scales linearly with vacuum heat current.

Key points

• A driven quantum system with an imperfect counter register can exhibit a finite, positive arrow of time while microscopic entropy production is infinite.
• The system is a degenerate parametric oscillator below threshold, coupled to a thermal reservoir through repeated interactions with bosonic ancillas.

Context

This finding challenges the assumption that finite coarse-grained measurements of entropy production imply finite microscopic irreversibility. It occurs in a driven quantum system where absorption is forbidden into the vacuum bath, creating a support mismatch between trajectory laws that allows finite measurements to coexist with infinite microscopic entropy production.

Limitations

The evidence is limited to a theoretical construction of a driven quantum system below threshold. The specific detector parameters, observation duration, and exact values of the heat current are not provided. The relationship between the hidden contribution and the vacuum heat current is given as an asymptotic expansion, not a precise formula. No experimental data or validation of the system's physical realizability is included.

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