The microscopic origins of charge noise in solid-state qubits

In solid-state quantum computing, charge noise is a primary source of decoherence. Whether you are working with superconducting qubits, semiconductor quantum dots, or color centers, the electric field from fluctuating charges in the environment couples directly to the qubit's energy levels, causing phase drift.

The dominant contributor is surface noise. Trapped charges on oxides and interfaces exhibit drift-diffusion dynamics, hopping between localized defect sites. Phenomenologically, this manifests as a 1/f noise spectrum, which is exceptionally difficult to filter out because it grows stronger at low frequencies.

In our calculations, we model these charge fluctuations using a master equation coupled to a Poisson solver to map out the spatial dependence of the noise. By understanding how the electric field power spectral density scales with the distance from the surface, we can design device geometries that minimize noise exposure.

Ultimately, materials science and surface passivation are as critical as quantum control. Cleaning the surface oxide interfaces and using specialized capping layers are the most promising avenues for extending coherence times in heterogeneous photonic and semiconductor devices.