Reversing the direction of heat flow using quantum correlations

TL;DR

This paper experimentally demonstrates reversing heat flow from cold to hot in a quantum system using initial quantum correlations, challenging classical thermodynamics principles.

Contribution

It shows that quantum correlations can reverse heat flow direction, providing new insights into quantum thermodynamics and information theory.

Findings

Heat flows from cold to hot with initial quantum correlations.

Quantum correlations enable control of heat transfer direction.

Experimental verification using NMR setup.

Abstract

Heat spontaneously flows from hot to cold in standard thermodynamics. However, the latter theory presupposes the absence of initial correlations between interacting systems. We here experimentally demonstrate the reversal of heat flow for two quantum correlated spins-1/2, initially prepared in local thermal states at different effective temperatures, employing a Nuclear Magnetic Resonance setup. We observe a spontaneous energy flow from the cold to the hot system. This process is enabled by a trade off between correlations and entropy that we quantify with information-theoretical quantities. These results highlight the subtle interplay of quantum mechanics, thermodynamics and information theory. They further provide a mechanism to control heat on the microscale.