Charge Noise Characterization in SiGe Triple-Dot Qubits

Gated semiconductor quantum dots are attractive candidates for quantum information processing because of the large existing base of fabrication processes providing nearly defect-free host materials and gate patterning techniques. Isotopically-enhanced silicon precursors are now routinely leveraged to create spin-based qubits with long coherence times [1]. Electrical control of these qubits is sensitive to unwanted charge fluctuations originating from the device itself. This noise can be mitigated -- but not eliminated -- through clever device designs and modes of operation [2,3]. Complementing these design and operation advances are the efforts to understand the origins of charge noise and methods to reduce the noise [4]. In this talk, I will review one of the promising spin qubits, Si/SiGe triple-quantum dots, and general techniques that have been developed to gain insight into what limits the performance of these devices. An emphasis will be placed on correlating qubit performance to simpler and more universal charge noise characterization methods. In particular, power spectral densities will be presented as a function of different device designs and temperatures. In addition, cross-correlation measurements will show the noise to be a local phenomenon. Simple characterization structures and methods will also be discussed that have general applicability to all semiconductor quantum-dot qubits in an effort to drive to a common understanding of the microscopic origins of charge noise in these systems.
[1] K. Eng et al. Science Advances 1, e1500214 (2015)
[2] M.D. Reed et al. Phys. Rev. Letters 116, 110402 (2016)
[3] F. Martins et al. Phys. Rev. Letters 116, 116801 (2016)
[4] B. M. Freeman et al. App. Phys. Letters 108, 253108 (2016)