Ergodicity Breaking and Quantum Many-Body Scars

In Plain English

Usually, when you drop an ice cube into hot coffee, the ice rapidly melts as its temperature rises to match its surroundings—a process known as thermalization.

This drive toward equilibrium is taken as a given in classical physics. However, the quantum world can surprise us. In our collaborative research, we successfully engineered special states called "Quantum Many-Body Scars."

Returning to the analogy, these scars act exactly like a quantum version of ice that stubbornly refuses to melt, even when sitting in hot coffee. By avoiding thermalization, these states preserve the memory of their initial conditions, offering a pathway toward creating stable quantum memory systems.

Research Summary

The breakdown of thermalization in isolated quantum systems remains one of the most intriguing frontiers in many-body physics. Our research explores the phenomenon of quantum many-body scars (QMBS)—rare, non-thermal eigenstates embedded within an otherwise chaotic spectrum.

In recent collaborative efforts, we have theoretically and experimentally demonstrated that spinor gases driven by spin-flopping fields serve as excellent platforms for investigating ergodicity breaking. We observed that specific initial states remain non-thermal at weak driving strengths despite the majority of the system thermalizing, providing clear evidence of QMBS. As driving strength varies, we map the smooth transition from integrability to weak ergodicity breaking, shedding light on how quantum information can persist against the natural tendency toward thermal equilibrium.