Hot Cools Faster: The Quantum Mpemba Effect express
The Mpemba paradox, hot water sometimes freezes faster than cold, has gained a quantum sequel. In the microworld, a particle pushed farther from the finish line gets there first. Experimenters demonstrated this on a single spin: like a racer, they pushed it farther from equilibrium, and it reached it faster than after a weak nudge.
The key is entropy, the measure of chaos. In quantum reality, greater disorder accelerates the march toward order. The irony is that the classical Mpemba effect is a capricious rarity, while its quantum counterpart is stable and predictable.
Engineers harnessed this trick: they embedded it into a micro-fridge and dramatically boosted its cooling capacity.
Original abstract
as written by the authors arXiv:2511.14552
Coherence is an inherently quantum property that deeply affects microscopic processes, including thermalization phenomena. A striking example is the quantum Mpemba effect (QME), in which a system can exhibit anomalous relaxation, thermalizing faster from a state initially farther from equilibrium than from one closer. Here, we experimentally investigate the genuine QME and observe how the dynamics of a spin-1/2 system interacting with a heat sink can be sped-up to equilibrium. Furthermore, we apply the QME in a quantum Otto refrigerator, thereby increasing its cooling power. This proof-of-concept experiment unveils new practical paths for improving quantum thermal tasks.
Although the Mpemba effect in a glass of water is not always observed and still sparks debate, its quantum sibling turned out to be more reliable and predictable.