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.
Highlights
Heat spontaneously flows from hot to cold in standard thermodynamics
We report the experimental demonstration of the reversal of heat flow for two initially quantum-correlated qubits prepared in local thermal states at different effective temperatures employing Nuclear Magnetic Resonance (NMR) techniques[21,22]
We have observed the reversal of the energy flow between two quantum-correlated qubits with different effective temperatures, associated with the respective populations of the two levels
Summary
Heat spontaneously flows from hot to cold in standard thermodynamics. the latter theory presupposes the absence of initial correlations between interacting systems. It has been theoretically suggested that for quantum-correlated local thermal states, heat might flow from the cold to the hot system, effectively reversing its direction[9,10,11,12]. We report the experimental demonstration of the reversal of heat flow for two initially quantum-correlated qubits (twospin-1/2 systems) prepared in local thermal states at different effective temperatures employing Nuclear Magnetic Resonance (NMR) techniques[21,22]. We observe a spontaneous heat current from the cold to the hot spin and show that this process is made possible by a decrease of their mutual information. We theoretically derive and experimentally investigate an expression for the heat current that reveals the trade off between information and entropy
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