Inequalities for quantum-statistical response functions

Dani R. Castellanos, Petr Jizba

The Jarzynski equality, which relates equilibrium free-energy difference to an average of non-equilibrium work, plays a central role in modern non-equilibrium statistical thermodynamics. In this paper, we study a weaker consequence of this relation, known as Jarzynski's inequality, which can be formally obtained from the Jarzynski equality via Jensen's inequality. We identify and analyze several extensions of Jarzynski's inequality that go beyond its direct derivation from the Jarzynski equality. In particular, we consider chemical systems both in the linear-response regime and away from linear thermodynamics. Furthermore, by employing functional-integral techniques, we extend Jarzynski's inequality to many-body statistical systems described by quantum field theory. Salient issues, such as connections of the Jarzynski inequality with the maximum work theorem and the Landau--Lifshitz theory of fluctuations, are also discussed.

Eugen Fick, Günter Sauermann

Ming Yang

Bell inequalities exclude a broad class of local hidden-variable explanations of quantum correlations. A recurring objection is that the usual Bell form is static, whereas real measuring devices may contain local memory, stochastic dynamics, and measurement-induced disturbances of their hidden variables. We formulate this objection as a general transition-kernel model for dynamical hidden variables. The only locality assumption is imposed at the ontic level: conditional on the pre-measurement ontic state, the transition kernel and response function in each wing depend on the local setting but not on the distant setting or on distant post-measurement variables. Under measurement independence, all such dynamics can be absorbed into effective local response functions. The resulting probabilities have exactly the static Bell-local form and therefore obey the CHSH inequality. The result identifies the available escape routes for reproducing quantum correlations: violating ontic dynamical locality, violating measurement independence, or abandoning a classical hidden-variable ontology. As a consequence, local classical dynamical complexity cannot by itself spoof Bell-nonlocal statistics in device-independent protocols.

Peter Millington, Zong-Gang Mou, Paul M. Saffin +1 more

Abstract Inspired by Lefschetz thimble theory, we treat Quantum Field Theory as a statistical theory with a complex Probability Distribution Function (PDF). Such complex-valued PDFs permit the violation of Bell-type inequalities, which cannot be violated by a real-valued, non-negative PDF. In this paper, we consider the Classical-Statistical approximation in the context of Bell-type inequalities, viz. the familiar (spatial) Bell inequalities and the temporal Leggett-Garg inequalities. We show that the Classical-Statistical approximation does not violate temporal Bell-type inequalities, even though it is in some sense exact for a free theory, whereas the full quantum theory does. We explain the origin of this discrepancy, and point out the key difference between the spatial and temporal Bell-type inequalities. We comment on the import of this work for applications of the Classical-Statistical approximation.

Władysław Marcinek