Two-level systems (TLSs) are ubiquitous in amorphous materials and interfaces, yet their microscopic origin remains poorly understood. Superconducting qubits offer a unique platform to probe these defects individually, acting as a sensitive spectrometer of their local solid-state environment.

We show that non-Poissonian quantum jump statistics allow us to distinguish these long-lived TLSs from the standard Markovian bath. Wide-band spectroscopy based on this understanding, combined with pump-probe experiments, reveals individual TLSs with lifetimes of up to several seconds. This level of control opens new paths toward understanding the microscopic origin of TLSs and exploring their potential as a novel memory resource