# Anomalous Charge Noise in Superconducting Qubits

## TL;DR

This study characterizes charge noise in superconducting qubits, revealing a 1/f^α noise spectrum with large amplitude jumps, challenging existing models and suggesting new mechanisms like charge drift or patch potentials.

## Contribution

It provides detailed measurements of charge noise in superconducting qubits, highlighting large amplitude jumps and scale dependence, which are novel compared to prior work.

## Key findings

- Charge noise scales as 1/f^1.93 over 5 decades.
- Large charge jumps exceeding 0.1e are observed.
- Charge noise depends on device scale, indicating new models.

## Abstract

We have used Ramsey tomography to characterize charge noise in a weakly charge-sensitive superconducting qubit. We find a charge noise that scales with frequency as $1/f^\alpha$ over 5 decades with $\alpha = 1.93$ and a magnitude $S_q(\text{1Hz})= 2.9\times10^{-4}~e^2/\text{Hz}$. The noise exponent and magnitude of the low-frequency noise are much larger than those seen in prior work on single electron transistors, yet are consistent with reports of frequency noise in other superconducting qubits. Moreover, we observe frequent large-amplitude jumps in offset charge exceeding 0.1$e$; these large discrete charge jumps are incompatible with a picture of localized dipole-like two-level fluctuators. The data reveal an unexpected dependence of charge noise on device scale and suggest models involving either charge drift or fluctuating patch potentials.