Morris R G E, van Loo A F, Kosen S, Karenowska A D
Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK.
Sci Rep. 2017 Sep 14;7(1):11511. doi: 10.1038/s41598-017-11835-4.
We report measurements made at millikelvin temperatures of a superconducting coplanar waveguide resonator (CPWR) coupled to a sphere of yttrium-iron garnet. Systems hybridising collective spin excitations with microwave photons have recently attracted interest for their potential quantum information applications. In this experiment the non-uniform microwave field of the CPWR allows coupling to be achieved to many different magnon modes in the sphere. Calculations of the relative coupling strength of different mode families in the sphere to the CPWR are used to successfully identify the magnon modes and their frequencies. The measurements are extended to the quantum limit by reducing the drive power until, on average, less than one photon is present in the CPWR. Investigating the time-dependent response of the system to square pulses, oscillations in the output signal at the mode splitting frequency are observed. These results demonstrate the feasibility of future experiments combining magnonic elements with planar superconducting quantum devices.
我们报告了在毫开尔文温度下对与钇铁石榴石球体耦合的超导共面波导谐振器（CPWR）所进行的测量。将集体自旋激发与微波光子混合的系统最近因其潜在的量子信息应用而备受关注。在本实验中，CPWR的非均匀微波场使得能够与球体中的许多不同磁振子模式实现耦合。通过计算球体中不同模式族与CPWR的相对耦合强度，成功识别出了磁振子模式及其频率。通过降低驱动功率，将测量扩展到量子极限，直到平均而言CPWR中存在的光子少于一个。研究系统对方波脉冲的时间相关响应时，观察到了在模式分裂频率处输出信号的振荡。这些结果证明了未来将磁振子元件与平面超导量子器件相结合的实验的可行性。
