Non-equilibrium dynamics in quantum many-body systems lies at the heart of the current development of modern quantum science and technology where rich phenomena have been found during recent years, especially in synthetic quantum platforms such as ultracold atoms and superconducting qubit.

However, simple and universal rules behind non-equilibrium quantum dynamics are still lacking. Non-equilibrium dynamics usually involve highly excited states beyond the conventional low-energy universality. The main difficulties in discovering universal behavior in non-equilibrium dynamics arise from the strongly correlating nature and the complexity of non-equilibrium many-body systems, as well as the experimental challenges associated with high-precision quantum control of these systems.

In this study, researchers employed solid-state nuclear spin systems, which are natural and adjustable experimental platforms for studying the non-equilibrium dynamics of quantum many-body systems. Based on years of expertise in quantum control and quantum simulation of nuclear spin systems, they designed the pulse sequences to high-precisely control the 1H nuclear spins in adamantane (C10H16) powder (each grain containing approximately 109 to 1012 molecules), and realized randomly interacting spin models with adjustable anisotropic parameters. The randomness arises from the random orientations between the lattice axes in different grains and the static magnetic field.

Then, researchers observed a new phenomenon that the spin depolarization dynamics shows a clear transition from monotonic to oscillatory decay as the anisotropic parameter changed. They found that the behavior of the spin depolarization dynamics can be universally described by two parameters. By comparing the experimental observations with several different theoretical approaches, researchers offered a comprehensive theoretical explanation of non-equilibrium quantum many-body dynamics.

This study serves as an excellent example of how quantum information technology can be used to discover new physical laws. Besides, the methods and techniques used in this study provide new insights for other physical systems such as ultracold atoms or molecules.

Dominating interaction processes behind the spin depolarization dynamics. (Image by Prof. DU’s team)