Quantum Mpemba Effect Experimentally Verified: Accelerating Relaxation in Quantum Systems

Researchers from China, Britain, and Singapore have experimentally demonstrated the quantum Mpemba effect, showcasing that specific initial conditions can accelerate relaxation in quantum systems. This phenomenon mirrors the classical Mpemba effect, where, paradoxically, hot water can cool faster than cold water under particular conditions.

The team's findings, published in Nature Communications, involved using single trapped ions to exponentially accelerate the relaxation of a pure state into a stationary state. This is a key characteristic of the strong Mpemba effect (sME). The research provides strategies for designing and analyzing open quantum systems, potentially benefiting quantum batteries and other technologies.

The study highlights that the decay rate of a system in a sME state is greater than others, emphasizing the influence of initial conditions on equilibrium speed. While classical systems are described by the Fokker-Planck equation with temperature as the key variable, quantum systems follow the Lindblad master equation, where the energy of the sME state is crucial.

Researchers created a pure state with zero overlap with the slowest decay mode (SDM) by trapping a Ca ion and coupling three energy levels using laser interactions. By tuning Rabi frequencies, they observed different relaxation regimes. The transition from sME to weak ME occurred when the ratio of Rabi frequencies equaled the Liouvillian exceptional point (LEP).

Hui Jing, a physicist at China's Hunan Normal University, notes that the quantum sME's relaxation path includes the LEP, where the eigenvalue of the dynamical generator changes from real to complex. This work offers an alternative method for increasing ion cooling rates and enhancing quantum battery efficiency. Future research will focus on the quantum Mpemba effect's behavior at the LEP, potentially leading to even faster decay rates.