Improved control of quantum dots in Ge/SiGe quantum wells for spin qubit applications*

Much work on semiconductor spin qubits has focused on extending capabilities and understanding limitations of Si andGaAs.In parallel,alternative materials are being scrutinized for potential advantages in terms of coherence times,control,and extensibility,without sacrificing key features.One such quantum well system,undoped strained Ge/SiGe,appears promising as a candidate spin qubit host due to low disorder,small hole effective mass, and large spin-orbit coupling,and has already been used to demonstrate basic single quantum dots.We take the next steps toward hole spin qubits by preparing a double quantum dot in a one-layer gate structure,then using multilayer gate stacks to demonstrate improved quantum dot control.