Highly stable two-level current fluctuation in complex oxide heterostructures

Two-level systems based on point defects in dielectric oxides offer promising entropy source for random number generators. The random telegraph noise (RTN) generated by the two-level systems is ideal for creating random bit-strings for advanced computing and cryptographic technologies. However, in classical oxide systems, RTN signals often suffer from instability due to undesired defect migration and metastable electronic states. Herein, we present a two-level quantum system based on SrRuO3/LaAlO3/Nb-doped SrTiO3 heterostructure, which incorporates two different types of point defects, oxygen vacancies and antisite Ti defects. Temporal electron localization at antisite defects alters the energy levels of nearby oxygen vacancies through instantaneous Coulomb interaction, resulting in two-level current fluctuation across the interface. The RTN-like current signals exhibit high stability at room temperature. We utilize the stable two-level fluctuations to generate random bit-strings and confirm their applicability in practical stochastic machine learning algorithms for image super-resolution. This study provides a guideline for designing reliable entropy sources by exploiting the complementary interactions between cation and anion point defects in oxide-based electronic systems, essential for hardware-based random number generators.