High Pockels and Piezoelectric Performance in Thin-Film Strontium Titanate for Cryogenic Electro-optical Systems

Quantum computers encounter various obstacles when scaling up qubit numbers and enhancing computational power. For superconducting qubits, one such challenge is the radio frequency (RF) bottleneck that occurs between the cryostat-contained qubit processor and the room temperature control and readout electronics. Similar to developments in classical systems, one proposed solution is to replace RF connections with optical fibers, leading to hybrid architectures where RF-qubits perform computation and optical qubits facilitate remote communication. Nevertheless, electro-optical (EO) transducers capable of efficiently converting RF-qubits to optical qubits with unity efficiency have not yet been realized. Achieving unity efficiency relies on materials that exhibit low losses, strong nonlinearities, and effective confinement of the electro-magnetic field. Ongoing research explores devices utilizing the Pockels and piezoelectric effects in lithium niobate, a common material in long-range optical communication. This presentation discusses recent progress involving thin-film strontium titanate, which demonstrates Pockels and piezoelectric coefficients significantly higher than those of lithium niobate [1,2]. The focus is on GHz Pockels response, thin-film piezoelectricity, and optical losses of this new class of material.