Efficient Analysis of Low Frequency Noise in Quantum Devices

Noise can limit the prospects of semiconducting quantum devices through its effect on the coherence time, gate fidelities, readout fidelities, and device integration. Improving these prospects first requires characterizing the noise and the variations within a device and between devices of different design. Typically, noise is analyzed in the frequency domain via the power spectral density (PSD) and parameterized by a coefficient at 1 Hz and a single power law exponent, S = Af^α. Often, however, data are not well modeled by a single power law and hint at a stronger frequency dependence below ∼ 1 Hz. Thus, to obtain representative behavior, many time-consuming measurements must be taken creating a bottleneck in device feedback. Here, we present systematic measurements of the noise in industrially fabricated metal-oxide-semiconductor quantum dots analyzed in the frequency and time domains using a technique borrowed from the atomic clock community known as the Allan variance. The combination of these techniques allows for more complete characterization of the noise than is possible with the PSD alone. It also provides a map onto integer noise exponents (such as α = -1 and α = -2) and, with modification, a measure of the expected drift in the device as a function of time.