Correlations of spin splitting and orbital fluctuations due to 1/f charge noise in the Si/SiGe quantum dot

Abstract

Fluctuations in electric fields can change the position of a gate-defined quantum dot (QD) in a semiconductor heterostructure. In the presence of magnetic field gradient, these stochastic shifts of electron's wavefunction lead to fluctuations of electron's spin splitting. The resulting spin dephasing due to charge noise limits the coherence times of spin qubits in isotopically purified Si/SiGe quantum dots. We investigate the spin splitting noise caused by such a process due to microscopic motion of charges at the semiconductor-oxide interface. We compare effects of isotropic and planar displacement of the charges and estimate their densities and typical displacement magnitudes that can reproduce experimentally observed spin splitting noise spectra. We predict that for a defect density of 1010 cm−2, visible correlations between noises in spin splitting and in energy of electron's ground state in the quantum dot are expected.