Links + Resources
Overview: This Quanta article reports an experiment in which heat flowed from a colder quantum system to a hotter one, the reverse of its usual direction. Researchers used two correlated nuclear spins in a molecule; as their initial correlations weakened, those correlations acted as a resource enabling the reversed heat flow. The result does not violate the second law of thermodynamics when correlations are included in the accounting, and it does not mean time literally ran backward or that time travel became possible. It demonstrates how information stored in correlations can influence heat flow at microscopic scales.
Further Reading & Explanatory Resources
- Quantum thermodynamics explained: The Quantum Thermodynamics Revolution — Quanta Magazine. An accessible introduction to the connections among energy, entropy, information, and quantum machines, including Maxwell’s demon.[3]
- The arrow of time in context: A Debate Over the Physics of Time — Quanta Magazine. Explores why entropy gives everyday events a direction and why the universe’s low-entropy past matters; broader context rather than an explanation of this particular experiment.[4]
- Original research (technical): Reversing the direction of heat flow using quantum correlations — Micadei et al. Free access to the study behind the article, describing the nuclear magnetic resonance experiment and its information-theoretic explanation. The study was subsequently published in Nature Communications 10, 2456 (2019): published paper.[2]