2020, Struck, Tom, Hollmann, Arne, Schauer, Floyd, Fedorets, Olexiy, Schmidbauer, Andreas, Sawano, Kentarou, Riemann, Helge, Abrosimov, Nikolay V., Cywiński, Łukasz, Bougeard, Dominique, Schreiber, Lars R.

The original version of this Article omitted the following from the Acknowledgements: “This work has also been funded by the National Science Centre, Poland under QuantERA program, Grant No. 2017/25/Z/ST3/03044.” This has now been corrected in both the PDF and HTML versions of the Article. © 2020, The Author(s).

2020, Struck, Tom, Hollmann, Arne, Schauer, Floyd, Fedorets, Olexiy, Schmidbauer, Andreas, Sawano, Kentarou, Riemann, Helge, Abrosimov, Nikolay V., Cywiński, Łukasz, Bougeard, Dominique, Schreiber, Lars R.

We identify the dominant source for low-frequency spin qubit splitting noise in a highly isotopically-purified silicon device with an embedded nanomagnet and a spin echo decay time T2echo = 128 µs. The power spectral density (PSD) of the charge noise explains both, the clear transition from a 1/f2- to a 1/f-dependence of the splitting noise PSD as well as the experimental observation of a decreasing time-ensemble spin dephasing time, from T2*˜ 20 µs, with increasing measurement time over several hours. Despite their strong hyperfine contact interaction, the few 73Ge nuclei overlapping with the quantum dot in the barrier do not limit T2*, likely because their dynamics is frozen on a few hours measurement scale. We conclude that charge noise and the design of the gradient magnetic field are the key to further improve the qubit fidelity in isotopically purified 28Si/SiGe. © 2020, The Author(s).