Electrically controlled spin qubit in Ge/Si nanowire with fast radio-frequency readout

2018 Fiscal Year Final Research Report

• Project/Area Number: 17K14076
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Nanostructural physics
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: SUN Jian 国立研究開発法人理化学研究所, 開拓研究本部, 客員研究員 (70792357)
• Project Period (FY): 2017-04-01 – 2019-03-31
• Keywords: spin-orbit interaction / quantum dot / nanowire

Outline of Final Research Achievements

We obtained the optimized ohmic contact to Ge/Si nanowire. With such devices, we achieved quasi-ballistic transport in the nanowire and measured quantized conductance features. The helical spin state was detected as a re-entrant conductance feature residing on conductance plateaus of 2e^2/h, which is a strong experimental support of the existence of strong spin-orbit interaction. We extracted a strong spin-orbit energy of 2.1 meV and g-factor of 3.6 (Nano Lett. 2018).
We also fabricated the gate-defined quantum dots in nanowire with sub-100 nm pitch finger gates and exfoliated hBN dielectric. A microwave transmission line resonator connected to the source is utilized to for the fast readout. Moreover, the qubit energy can be separately tuned by the chemical potential difference and the tunnel coupling between the adjacent dots, thus switching on and off the coupling. The hole-photon coupling strength is evaluated to be in the magnitude of several tens of MHz. (Nano Lett. 2019)

Free Research Field

ナノ構造物理

Academic Significance and Societal Importance of the Research Achievements

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