The Quantum Mpemba Mystery: When Greater Chaos Speeds Up Order ⚡ экспресс
The quantum Mpemba effect (QME) — the paradoxical acceleration of symmetry restoration with a larger initial breaking — is investigated on a superconducting processor with a fully-connected architecture and tunable interactions to control coupling regimes, potentials, and initial states. Symmetry restoration was quantified via entanglement asymmetry, computed from the density matrix reconstructed by quantum state tomography. In the strong short-range coupling regime, when quenching from a tilted Néel state, crossings of asymmetry curves were observed, confirming QME. In the intermediate regime, synchronization of entanglement asymmetry and entanglement entropy dynamics indicated suppression of the effect. QME revives upon introducing linear local potentials or quenching from a tilted ferromagnetic state, with the latter being robust to local disorder. Flexible modulation of QME via multiple controllable parameters is demonstrated, deepening the understanding of non-equilibrium dynamics of many-body systems and opening avenues for quantum information applications.
In everyday life, hot water sometimes freezes faster than cold water—that's the Mpemba effect. In quantum systems, a similar paradox occurs: a more strongly broken symmetry restores itself faster, like a compressed spring that recoils more sharply if squeezed tighter.
Physicists built such a 'spring' on a superconducting chip—a platform that John Bardeen helped to develop. They set an initial state, as if bending the spring, and tracked a special measure of order—an analog of temperature for chaos. It turned out that by changing the strength of interactions between components, you can switch the accelerated recoiling on and off. With long-range interactions, the effect disappeared; with strong nearest-neighbor coupling, it flourished.
By adding a gentle tilt, the scientists reignited the effect, and small disturbances couldn't kill it. As John Preskill showed, such techniques help circumvent errors. So even the familiar laws of the standard model hold surprises when it comes to non-equilibrium behavior.
🎯 The Mpemba effect is named after Tanzanian Erasto Mpemba, who as a schoolboy noticed the unusual freezing of hot milk and stubbornly proved the effect's existence. Curiously, Aristotle had mentioned a similar phenomenon long before.
🎬 Sci-fi writers often describe how chaos births order, like self-assembling nanobots in Stanisław Lem's works. The quantum Mpemba effect feels like a lab illustration of how matter can surprise us with unexpected behavior.