Single-Shot Readout of a S/T Qubit with a Cryogenic AC-Coupled HBT Amplifier in a Lithographic MOS Double Quantum Dot

Existing silicon fabrication capabilities can be exploited to form qubits in MOS nanostructures. However, it has been challenging to produce few-electron lithographically defined MOS double quantum dots (DQD) with tunable tunnel coupling (demonstrated in GaAs and Si-SiGe). We introduce a Si-MOS DQD device utilizing a foundry-compatible single poly-Si gate layer design. We demonstrate a well-defined few-electron DQD and tune the inter-dot tunnel coupling over several orders of magnitude. We demonstrate Pauli spin blockade readout of a two-electron S/T system and analyze the DQD properties via coherent S/T manipulations. The qubit state is read out in single shot with a SiGe HBT cryogenic amplification circuit, with a noise floor of 25 fA/Hz^1/2 and readout sensitivity of 360x10^-6 Hz^-1/2. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.