Probing non-adiabaticity in a quantum Otto cycle through quantum texture and imaginarity
Jonas F. G. Santos
Finite-time driving in quantum thermodynamic cycles inevitably generates coherences in the instantaneous energy basis, leading to quantum friction and degrading the operational performance. In this work, we demonstrate that the non-adiabatic inner friction produced during unitary driving of a two-level system can be faithfully quantified by combining two distinct resource-theoretic notions: quantum texture (rugosity) and imaginarity. We show that neither rugosity nor imaginarity alone is sufficient to track the total non-adiabaticity, and we introduce a combined witness, which is strictly non-negative and vanishes if and only if the driving is quasi-static. Applying this framework to a finite-time quantum Otto refrigerator, we establish an exact closed-form relation connecting the coefficient of performance directly to the quantum texture and imaginarity, evaluated at the end of the unitary compression and expansion strokes. Furthermore, we show that local minima of the non-adiabatic witness accurately identify the operating regimes that maximize cooling performance. Our findings provide a geometric and resource-theoretic foundation for inner friction, offering practical diagnostic tools for optimizing finite-time quantum thermal machines.
quant-pharXiv:2611.02291•Nov 3, 2026