Influence of charge noise on foundry-fabricated spin qubit*

            Semiconductor quantum dots represent a promising platform for quantum information processing [1]. Among the various technologies belonging to this category, silicon has low-spin-orbit interaction, and can be purified into its zero nuclear spin isotopes. Electron spins in silicon therefore stand out as potential qubits given their long coherence times and demonstrated fault-tolerant single qubit operations [2]. In this context, quantum dots (QDs) formed in CMOS classical electronics offer a path towards scalable quantum computing, by leveraging industrial fabrication foundries [3], and potentially make reliable spin qubits

However, fluctuating charge traps in the vicinity of QDs have a strong impact on the characteristic of spin qubits by modifying both their static and dynamical properties.

In this context, we present how one can characterize the influence of charge noise on foundry-fabricated devices at low frequency. We will focus on the fluctuation of the electrochemical potential and valley splitting using tunneling spectroscopy and relaxometry at the hotspot respectively.

In a second time, we present analysis of charge noise at high frequency. For this purpose, we have performed dynamical decoupling on a single-electron spin qubit and extract noise power spectral density at large decoupling rate. The obtained PSD indicates that coherence is likely dominated by charge noise and agrees with the extrapolation of low frequency charge noise probed by standard method.

In conclusion, the low amplitude of charge noise measured in these foundry-fabricated structures makes it a good platform toward the realization of high-quality spin-qubits.

[1] Loss, Daniel, and David P. DiVincenzo. "Quantum computation with quantum dots." Physical Review A 57, 120 (1998).

[2] Yoneda, Jun, et al. "A quantum-dot spin qubit with coherence limited by charge noise and fidelity higher than 99.9%." Nature nanotechnology 13, 102 (2018).

[3] Maurand, R., et al. "A CMOS silicon spin qubit." Nature communications 7, 13575 (2016).