Cryogenic microwave mixing and phase control in superconducting quantum paraelectric resonator

Scaling quantum processors requires cryogenic microwave components to minimize thermal load and wiring complexity. However, conventional microwave components such as mixers and phase shifters perform poorly at millikelvin temperatures. Here, we report an SrTiO 3 (STO)-based microwave frequency mixer and phase shifter operating at sub-Kelvin temperatures. Utilizing the effective χ (2) nonlinearity of STO in the quantum paraelectric state, induced by a static or oscillating field, we achieve efficient microwave frequency mixing. Our device features an aluminum superconducting coplanar waveguide resonator on STO, which resonantly enhances mixing characteristics. The exceptionally high field-tunable dielectric constant of STO—approximately 30,000—allows for highly compact architectures and facilitates voltage-controlled phase shifting. Furthermore, we demonstrate multi-tone frequency mixing via phase modulation, facilitating spectral filtering and shaping. These STO-based devices provide a transformative approach to the generation of intricate microwave waveforms, tailoring control and readout signals in multi-qubit systems and paving the way for co-located quantum-classical integration.