A single atom trapped in a laser can be forced to cool down faster if it starts off significantly hotter than its surroundings.
April 24, 2026
Original Paper
Observation of quantum multi-Mpemba effect in a trapped-ion system
arXiv · 2604.21320
The Takeaway
Trapped-ion systems exhibit a quantum version of the Mpemba effect where a system further from equilibrium relaxes faster than one closer to it. This phenomenon is famous in the macroscopic world as hot water freezing faster than cold water, but it was never proven in the quantum realm. The experiment shows multiple crossings where the hotter system overtakes the cooler one on its way to the ground state. This happens because the initial high-energy state allows the particle to skip over certain mathematical bottlenecks in its evolution. Controlling these relaxation speeds could help engineers reset quantum computers much faster than current limits allow.
From the abstract
The quantum Mpemba effect (ME) in Markovian systems is conventionally explained by a smaller overlap between the initial state and the slowest decay mode (SDM). Such state, initially farther away from equilibrium or steady state, relaxes faster than closer ones, resulting to a crossing of their trajectories. This picture, by neglecting the transient dynamics, holds in the long-time limit. Here we experimentally observe multiple trajectory crossings (multi-ME) in the relaxation dynamics of a trap