Bockstiegel C, Wang Y, Vissers M R, Wei L F, Chaudhuri S, Hubmayr J, Gao J
National Institute of Standards and Technology, Boulder, Colorado 80305, USA.
Quantum Optoelectronics Laboratory, Southwest Jiaotong University, Chengdu, Sichuan 610031, China.
Appl Phys Lett. 2016 May 30;108(22). doi: 10.1063/1.4953209. Epub 2016 Jun 3.
We present a tunable coupler scheme that allows us to tune the coupling strength between a feedline and a superconducting resonator 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 . We have demonstrated tuning over a factor of 40, between ~ 5.5 × 10 and ~ 2.3 × 10, 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.
我们提出了一种可调谐耦合器方案，该方案使我们能够在很宽的范围内调节馈线与超导谐振器之间的耦合强度。在该方案中，我们用由20nm NbTiN薄膜制成的50Ω集总元件非线性传输线对馈线进行分流。通过注入直流电流，非线性动态电感发生变化，分流谐振器的有效阻抗会周期性地从短路变为开路，从而调节耦合强度和耦合品质因数。通过施加小于3.3mA的直流电流，我们已证明对于一个4.5GHz的谐振器，其耦合强度可在约5.5×10到约2.3×10之间实现40倍的调节。我们的可调谐耦合器方案易于实现，可能在超导探测器以及量子计算/信息实验中得到广泛应用。
