Stability of long ion chains versus catastrophic melting collisions: a combined numerical and experimental study

For scalable quantum computing with trapped atomic ions, a stable ion chain held in ultrahigh vacuum conditions is a pre-requsite. However, collisions with the residual background gas molecules can ''melt'' the ion chain: the imparted kinetic energies are high enough such that the Coulomb crystal is heated to the gas phase. Currently this problem presents a significant challenge to the number of qubits for compact trapped ion quantum computers in room temperature setups. It is also an interesting classical Floquet many-body problem in its own right: under periodic driving and non-linear Coulomb interactions, the trajectories of the ions can be classically chaotic. Here, we study the dynamics of multiple ions in a linear Paul-trap through combined numerical and experimental approaches, and find how different regions of the trap parameter space affect the dynamics of the ion chains and the melting probabilities. Contrary to the commonly held belief of radio-frequency heating induces melting, we show that the melting arise from the driven-dissipative competitions in the many-body system.