Probing Low-Frequency Charge Noise in Few-Electron CMOS Quantum Dots

Abstract

Charge noise is one of the main sources of environmental decoherence for spin qubits in silicon, presenting a major obstacle in the path towards highly scalable and reproducible qubit fabrication. Here we demonstrate in-depth characterization of the charge noise environment experienced by a quantum dot in a CMOS-fabricated silicon nanowire. We probe the charge noise for different quantum dot configurations, finding that it is possible to tune the charge noise over two orders of magnitude, ranging from $1\phantom{\rule{0.2em}{0ex}}\text{\ensuremath{\mu}}{\mathrm{eV}}^{2}/\mathrm{Hz}$ to $100\phantom{\rule{0.2em}{0ex}}\text{\ensuremath{\mu}}{\mathrm{eV}}^{2}/\mathrm{Hz}$. In particular, we show that the top interface and the reservoirs are the main sources of charge noise, and their effect can be mitigated by controlling the quantum dot extension. Additionally, we demonstrate a method for the measurement of the charge noise experienced by a quantum dot in the few-electron regime. We measure a comparatively high charge noise value of $40\phantom{\rule{0.2em}{0ex}}\text{\ensuremath{\mu}}{\mathrm{eV}}^{2}/\mathrm{Hz}$ at the first electron, and demonstrate that the charge noise is highly dependent on the electron occupancy of the quantum dot.