Fig. 1: Pump-quench control of multi-particle systems.
From: Structural reconfiguration of interacting multi-particle systems through parametric pumping
a Selective excitation of state A in a system of trapped atoms, creating a dark state B. The vertical axis indicates the potential energy of the system, Epot. When state A is excited by light with appropriate energy, it will be pumped into an excited state (orange arrow), from which it can randomly decay into one of the base states (black arrows). State B cannot be activated by incident light; thus, pumping concentrates atoms in state B. b Cycling between pumping and quenching to create an absorbing 'quiet' state, which does not rely on the presence of well-defined potential energy levels and therefore is not limited to conservative systems. The vertical axis indicates the kinetic energy, Ekin, where Ekin = 0 refers to a base state of the system. By activating a multi-particle system’s vibration mode with parametric pumping, the system will oscillate to the point of transitioning into an unstable state (red arrow). When the pumping is turned off, the system in the unstable state is quenched by damping and will randomly decay back into one of the base states. By cycling between pumping and quenching, the time-averaged outcome is the creation of an absorbing state B, similar to the diagram in (a). c–f Application of pump-quench cycling to control the configuration of, c an acoustically levitated cluster of five particles, d a simulated cluster of a rod and two spheres, e a simulated cluster of 13 spheres, and f the size of an acoustically levitated granular raft.
