Electron-on-neon (eNe) charge states coupled to superconducting circuits are a promising platform for quantum computing. Control over the formation of these charge states requires techniques to track and control the growth of solid $\mathrm{Ne}$ films on the circuit surface. We demonstrate a real-time $\mathrm{Ne}$ film-growth monitor using high-transition-temperature (high-$T_c$) YBCO microwave resonators. The high $T_c$ enables tracking of the film thickness near $\mathrm{Ne}$’s triple temperature and below. Across more than 300 solidification experiments, we find that the final $\mathrm{Ne}$ thickness varies stochastically from a few nanometers to a few microns for films solidified from the liquid phase. By increasing the driving power in the resonator, we consistently reduce the final thickness to below 100 nm. These results represent an important step toward controlled formation of $\mathrm{Ne}$ films for eNe qubits and highlight the broader utility of high-$T_c$ resonators for hybrid quantum systems.

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• Cryogenic technology
• Phase transitions
• Quantum information with solid state qubits
• Noble gases
• Quantum fluids & solids
• Surface growth
• Thin films
• Microwave techniques