Multi-level charge fluctuations in a Si/SiGe double quantum dot device

A candidate explanation for charge noise in semiconductor quantum dot devices is the fluctuation

of an ensemble of discrete two-level charge noise sources. A large variety of such fluctuators results

in Gaussian 1/f noise; however, significant deviation from Gaussianity is routinely observed that

may inform models of the underlying contributors to charge noise. Here we analyze multi-level

charge fluctuations present in a Si/SiGe double quantum dot device over a range of device voltage

and temperature values to probe the response of the charge fluctuations to changing operating con-

ditions. We perform algorithmically assisted drift detection and change point detection to detrend

the data and remove a slow fluctuator component, as a preprocessing step. We then perform model

comparison on the residual, post-processed time series between different n-level fluctuator (nLF)

factorial hidden Markov models (FHMMs) (2x2LF, 3LF, and 4LF), finding that although in most

voltage configurations the 2x2LF model is preferred, there is a particular region of device space

where the 4LF model outperforms the other models, indicating an emergent conditional rate de-

pendence between the constituent 2LFs. Finally, we fit a phenomenological, detailed balance model

to the extracted 2x2LF rate data, yielding lever arm estimates in the range of −2μeV/mV up to

4μeV/mV between the two 2LFs and nearby gate electrodes.