Microscopic bath effects on noise spectra in semiconductor quantum dot qubits

TL;DR

This paper investigates how microscopic bath effects induce 1/f noise in semiconductor quantum dot qubits, showing that temperature fluctuations in small baths can explain experimental charge noise data.

Contribution

It demonstrates that microscopic bath effects can produce 1/f noise in quantum dot qubits and improves noise modeling by considering sub-bath size, fitting experimental data with minimal fluctuators.

Findings

Temperature fluctuations cause 1/f noise in single two-level systems.

Modeling sub-bath size improves fit to experimental charge noise data.

As few as two fluctuators can explain observed noise spectra.

Abstract

When a system is thermally coupled to only a small part of a larger bath, statistical fluctuations of the temperature (more precisely, the internal energy) of this "sub-bath" around the mean temperature defined by the larger bath can become significant. We show that these temperature fluctuations generally give rise to 1/f-like noise power spectral density from even a single two-level system. We extend these results to a distribution of fluctuators, finding the corresponding modification to the Dutta-Horn relation. Then we consider the specific situation of charge noise in silicon quantum dot qubits and show that recent experimental data [E. J. Connors, et al., Phys. Rev. B 100, 165305 (2019)] can be modeled as arising from as few as two two-level fluctuators, and accounting for sub-bath size improves the quality of the fit.