Simulation of 1/f charge noise affecting a quantum dot in a Si/SiGe structure

Due to presence of magnetic field gradient needed for coherent spin control, dephasing of single-electron spin qubits in silicon quantum dots is often dominated by 1/f charge noise. We investigate theoretically fluctuations of ground state energy of an electron in gated quantum dot in realistic Si/SiGe structure. We assume that the charge noise is caused by motion of charges trapped at the semiconductor-oxide interface. We consider a realistic range of trapped charge densities, ρ∼10¹⁰ cm⁻², and typical lenghtscales of isotropically distributed displacements of these charges, δr≤1 nm, and identify pairs (ρ,δr) for which the amplitude and shape of the noise spectrum is in good agreement with spectra reconstructed in recent experiments on similar structures.

由于相干自旋操控（coherent spin control）所需的磁场梯度（magnetic field gradient）的存在，硅量子点（silicon quantum dots）中的单电子自旋量子比特（single-electron spin qubits）的退相（dephasing）通常由1/f电荷噪声（1/f charge noise）主导。我们从理论上研究了实际Si/SiGe异质结构栅控量子点中电子的基态能量（ground state energy）涨落。我们假设电荷噪声源于被俘获于半导体-氧化物界面（semiconductor-oxide interface）处的电荷的运动。我们考虑了俘获电荷密度ρ~10¹⁰ cm⁻²的典型取值范围，以及这些电荷的各向同性分布位移的典型尺度δr≤1 nm，并确定了使噪声谱（noise spectrum）的幅值与形状与近期针对同类结构开展的实验中重构得到的噪声谱吻合良好的(ρ,δr)参数对。