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美国卫生研究院文献>Applied Physics Letters
>A tunable coupler for superconducting microwave resonators using a nonlinear kinetic inductance transmission line
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A tunable coupler for superconducting microwave resonators using a nonlinear kinetic inductance transmission line
We present a tunable coupler scheme that allows us to tune the coupling strength between a feedline and a superconducting resonator in situ over a wide range. In this scheme, we shunt the feedline with a 50-Ω lumped-element nonlinear transmission line made from a 20 nm NbTiN film. By injecting a DC current, the nonlinear kinetic inductance changes and the effective impedance shunting the resonator periodically varies from a short to an open, which tunes the coupling strength and coupling quality factor Qc. We have demonstrated Qc tuning over a factor of 40, between Qc ~ 5.5 × 104 and Qc ~ 2.3 × 106, for a 4.5 GHz resonator by applying a DC current less than 3.3 mA. Our tunable coupler scheme is easy to implement and may find broad applications in superconducting detector and quantum computing/information experiments.
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