  In the context of engineered quantum systems, there is a demand for
superconducting tunable devices able to operate with high Q-factors at power
levels equivalent to only a few photons. In this work, we developed a 3D
microwave reentrant cavity with such characteristics ready to provide a very
fine-tuning of a high-Q resonant mode over a large dynamic range. This system
has an electronic tuning mechanism based on a mechanically amplified
piezoelectric actuator, which controls the resonator dominant mode frequency by
changing the cavity narrow gap by very small displacements. Experiments were
conducted at room and dilution refrigerator temperatures showing a large
dynamic range up to 4 GHz and 1 GHz, respectively, and were compared to a FEM
model simulated data. At elevated microwave power input, nonlinear thermal
effects were observed to destroy the superconductivity of the cavity due to the
large electric fields generated in the small gap of the reentrant cavity.
