Abstract
The coherence and fidelity of quantum dot (QD) spin qubits are fundamentally limited by charge noise arising from electrically active trap states at oxide interfaces, heterostructure boundaries, and within the bulk semiconductor. These traps introduce electrostatic fluctuations that couple to the qubit via spin-orbit interactions or charge-sensitive confinement potentials, leading to dephasing and gate errors. In this work, we present a general trap characterization framework for identifying and quantifying the spectral signatures of these trap states using AC impedance spectroscopy, deep-level transient spectroscopy (DLTS), and conventional capacitance-voltage (C-V) analysis. While our case study focuses on strained Ge/SiGe quantum well heterostructures, the approach is broadly applicable to other material systems and qubit types. We demonstrate that each class of traps (oxide interface, quantum well interface, and bulk) exhibits distinct fingerprints across frequency- and time-domain