| 研究実績の概要 |
In this year we firstly demonstrate a hole charge qubit defined by the electrostatically confined double quantum dots in the Ge/Si core/shell nanowires. The gate-defined quantum dots were realized in nanowire by electrostatical confinement using sub-100 nm pitch finger gates. And h-BN flake was transferred on to the gates and used as dielectric layer as it is a clean single crystal to improve device performance. The quantum dots device was coupled to a microwave transmission line resonator by connecting the source to the resonator. A typical 50Ω transmission line resonator fabricated using a 100nm-thick MoRe superconducting thin film via e-beam lithography and etching. The resonance is centered at 5.967 GHz with a Q-factor of ~6000. It allows us to a fast read out the charge states in the quantum dots using the resonator. We succeed to perform dissipative readout of charge states using the resonator. We probed the resonator at the center frequency and simultaneously detect both the magnitude and phase of the resonator transmission. We observe a clear honeycomb structure. From fitting of the response with a theoretical model we evaluate charge dipole coupling rates as high as 85 MHz but charge decoherence rates of 10s of GHz indicating operation in the dispersive regime. (Nano Letters, 19 (2), 1052-1060, 2019)
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