Interacting Two-Level Systems as a Source of 1/f Charge Noise in Quantum Dot Qubits

TL;DR

This paper models charge noise in quantum dot qubits as arising from interacting two-level systems (TLS) in a 2D bath, reproducing observed 1/f noise spectra and spatial correlations through simulations of elastic interactions.

Contribution

It introduces a novel model of interacting TLS via elastic strain fields to explain 1/f charge noise and correlations in quantum dot qubits.

Findings

1/f noise spectra match experimental observations

Cross correlations decrease exponentially with dot separation

Simulations reproduce qualitative features of charge noise

Abstract

Charge noise in semiconducting quantum dots has been observed to have a 1/f spectrum. We propose a model in which a pair of quantum dots are coupled to a 2D bath of fluctuating two level systems (TLS) that have electric dipole moments and that interact with each other, i.e., with the other fluctuators. These interactions are primarily via the elastic strain field. We use a 2D nearest-neighbor Ising spin glass to represent these elastic interactions and to simulate the dynamics of the bath of electric dipole fluctuators in the presence of a ground plane representing metal gates above the oxide layer containing the fluctuators. The interactions between the TLS cause the energy splitting of individual fluctuators to change with time. We calculate the resulting fluctuations in the electric potential at the two quantum dots that lie below the oxide layer. We find that 1/f electric potential noise spectra at the quantum dots and cross correlation in the noise between the two quantum dots are in qualitative agreement with experiment. Our simulations find that the cross correlations decrease exponentially with increasing quantum dot separation.