Kim Samuel, Shrekenhamer David, McElroy Kyle, Strikwerda Andrew, Alldredge Jacob
Research and Exploratory Development Department, Johns Hopkins University Applied Physics Laboratory, Laurel, MD, 20723, USA.
Electrical Engineering and Computer Science Department, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
Sci Rep. 2019 Mar 15;9(1):4630. doi: 10.1038/s41598-019-40891-1.
Here we consider a tunable superconducting cavity that can be used either as a tunable coupler to a qubit inside the cavity or as a tunable low noise, low temperature, RF filter. Our design consists of an array of radio-frequency superconducting quantum interference devices (rf SQUIDs) inside a superconducting cavity. This forms a tunable metamaterial structure which couples to the cavity through its magnetic plasma frequency. By tuning the resonant frequency of the metamaterial through an applied magnetic flux, one can tune the cavity mode profile. This allows us to detune the cavity initially centered at 5.593 GHz by over 200 MHz. The maximum quality factor approaches that of the empty cavity, which is 4.5 × 10. The metamaterial electromagnetic response is controlled via a low-frequency or dc magnetic flux bias, and we present a control line architecture that is capable of applying sufficient magnetic flux bias with minimal parasitic coupling. Together this design allows for an in-situ tunable cavity which enables low-temperature quantum control applications.
在这里，我们考虑一种可调谐超导腔，它既可以用作腔内量子比特的可调谐耦合器，也可以用作可调谐低噪声、低温射频滤波器。我们的设计由超导腔内的一系列射频超导量子干涉器件（rf SQUIDs）组成。这形成了一种可调谐超材料结构，该结构通过其磁等离子体频率与腔耦合。通过施加磁通量来调谐超材料的谐振频率，可以调谐腔模分布。这使我们能够将最初中心频率为5.593 GHz的腔失谐超过200 MHz。最大品质因数接近空腔的品质因数，即4.5×10。超材料的电磁响应通过低频或直流磁通量偏置来控制，并且我们提出了一种控制线架构，该架构能够以最小的寄生耦合施加足够的磁通量偏置。这种设计共同实现了一个原位可调谐腔，可用于低温量子控制应用。
