Physicists Create a Thermometer for Measuring ‘Quantumness’

Physicists have developed a novel method to detect quantum phenomena such as superposition and entanglement by observing "anomalous" heat flow, which appears to contradict the classical second law of thermodynamics. Traditionally, heat flows spontaneously from hotter to colder bodies, as stated by Clausius in 1850. However, at the quantum scale, heat can flow from colder to hotter systems due to quantum mechanical effects, without violating the fundamental thermodynamic principles. This quantum heat flow can be harnessed as a sensitive, non-destructive thermometer for measuring "quantumness" in physical systems. The technique involves coupling a quantum system to an information-storing system and a heat sink capable of absorbing energy. By measuring the temperature increase of the heat sink, researchers can infer the presence of quantum superposition or entanglement in the system. This approach not only provides a practical tool for verifying quantum resources in quantum computing but also deepens the understanding of the interplay between thermodynamics and information theory.