2017 Fiscal Year Research-status Report
Electrically controlled spin qubit in Ge/Si nanowire with fast radio-frequency readout
| Project/Area Number |
17K14076
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| Research Institution | Institute of Physical and Chemical Research |
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Principal Investigator |
孫 健 国立研究開発法人理化学研究所, 石橋極微デバイス工学研究室, 基礎科学特別研究員 (70792357)
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| Project Period (FY) |
2017-04-01 – 2019-03-31
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| Keywords | spin-orbit interaction / quantum point contact / quantum dot / spin qubit |
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| Outline of Annual Research Achievements |
Fabrication techniques have been developed for Ge/Si nanowire devices. We obtained the optimized ohmic contact to Ge/Si nanowire with Ti/Pd stack. With such devices, we achieved quasi-ballistic transport in the nanowire and measured quantized conductance features. We studied the spin-orbit interaction of the Ge/Si nanowire by measuring the quantized conductance. 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 (paper is under review). We also fabricated the gate-defined quantum dots in nanowire with sub-100 nm pitch finger gates and exfoliated hBN dielectric. A resonator connected to the source is utilized to for the fast readout.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
In the first fiscal year, the goal is to obtain optimized recipe of Ge/Si nanowire devices with clean Ohmic contact, study spin-orbit interaction and extract the Lande g-factor for the nanowire, and set-up the rf measurement for the quantum dots formed in the nanowire.
We fabricated high quality Ge/Si nanowire devices, with which we achieved quasi-ballistic transport in the nanowire and measured quantized conductance features.
The spin-orbit interaction of > 1 meV was verified by the helical spin state residing in the quantized conductance. Lande g-factor was extracted as 3.6 from the magneto-transport measurement.
Quantum dots were formed electrostatically using the local gates. The rf readout of the quantum dot can be done using a resonator connected to the drain of the nanowire.
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| Strategy for Future Research Activity |
In the coming fiscal year, we will continue the quantum dot measurements using the resonator. Firstly, the coupling of the quantum dots to resonator will be studied. The coherent control of the spin qubit will be verified by measuring the Rabi oscillations. We anticipate to measure the Larmor frequency from the magneto-dependence measurement.
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Research Products
(3 results)
