标题： 钽谐振器中涡流运动引起的损耗 显示英文标题

标题： Vortex Motion Induced Losses in Tantalum Resonators

摘要： 基于钽（Ta）的超导电路已被证明能够实现记录的量子比特退相干时间和品质因数，这促使人们仔细研究限制其性能的剩余损耗的微观起源。 我们最近表明，在低微波功率和毫开尔文温度下，基于Ta的谐振器中的损耗主要由两能级系统（TLSs）引起。 我们还观察到，某些器件在较低温度下表现出与组成薄膜的超导临界温度（Tc）不一致的指数激活损耗。 具体来说，直流电阻率测量显示Tc超过4 K，而使用这些薄膜制造的谐振器的微波测量显示损耗随温度呈指数增长，激活能低至0.3 K。在这里，我们对基于Ta的谐振器的结构和热力学特性进行了比较研究，并确定涡旋运动引起的损耗是热激活微波损耗的来源。 通过仔细的磁阻和X射线衍射测量，我们观察到增加的损耗发生在处于清洁极限的薄膜中，其中超导相干长度短于平均自由程。 在处于脏极限的薄膜中，涡旋运动引起的损耗被抑制，这些薄膜显示出可以钉扎涡旋的结构缺陷。 我们通过图案化明确钉扎涡旋来验证这一假设，并发现可以通过微加工抑制损耗。 显示英文摘要

摘要： Tantalum (Ta) based superconducting circuits have been demonstrated to enable record qubit coherence times and quality factors, motivating a careful study of the microscopic origin of the remaining losses that limit their performance. We have recently shown that the losses in Ta-based resonators are dominated by two-level systems (TLSs) at low microwave powers and millikelvin temperatures. We also observe that some devices exhibit loss that is exponentially activated at a lower temperature inconsistent with the superconducting critical temperature (Tc) of the constituent film. Specifically, dc resistivity measurements show a Tc of over 4 K, while microwave measurements of resonators fabricated from these films show losses that increase exponentially with temperature with an activation energy as low as 0.3 K. Here, we present a comparative study of the structural and thermodynamic properties of Ta-based resonators and identify vortex motion-induced loss as the source of thermally activated microwave loss. Through careful magnetoresistance and x-ray diffraction measurements, we observe that the increased loss occurs for films that are in the clean limit, where the superconducting coherence length is shorter than the mean free path. Vortex motion-induced losses are suppressed for films in the dirty limit, which show evidence of structural defects that can pin vortices. We verify this hypothesis by explicitly pinning vortices via patterning and find that we can suppress the loss by microfabrication.