Dielectric losses in multi-layer Josephson junction qubits
Dielectric losses in multi-layer Josephson junction qubits
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DOI：
10.1088/0953-2048/26/8/085010
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发表时间：
2013-08-01
影响因子：
3.6
通讯作者：
Prunnila, Mika
中科院分区：
文献类型：
--
作者：
Gunnarsson, David;Pirkkalainen, Juha-Matti;Prunnila, Mika
我们测量了约瑟夫森结相和transmon量子位的激发态寿命，所有这些都是用相同的可扩展多层工艺制造的。我们比较了去除隔离电介质SiNx之前和之后的相位量子比特的寿命，发现去除后的弛豫时间提高了四倍。连同来自transmon量子比特和共面波导谐振器的测量结果，这些测量表明寿命受到量子比特的介电成分的损耗的限制。我们已经提取了个别的损失贡献，从隧道结势垒，AlOx，隔离电介质，SiNx，和衬底，Si/SiO2，通过加权的总损耗与电场的部分在不同的电介质材料。我们的研究结果与其他研究结果一致，并补充了其他研究结果，表明超导量子比特可以用作介电材料高频表征的可靠工具。最后，我们讨论了设计和材料选择的变化如何将量子比特的寿命提高到4倍。
We have measured the excited state lifetimes in Josephson junction phase and transmon qubits, all of which were fabricated with the same scalable multi-layer process. We have compared the lifetimes of phase qubits before and after removal of the isolating dielectric, SiNx, and find a fourfold improvement of the relaxation time after the removal. Together with the results from the transmon qubit and measurements on coplanar waveguide resonators, these measurements indicate that the lifetimes are limited by losses from the dielectric constituents of the qubits. We have extracted the individual loss contributions from the dielectrics in the tunnel junction barrier, AlOx, the isolating dielectric, SiNx, and the substrate, Si/SiO2, by weighting the total loss with the parts of the electric field over the different dielectric materials. Our results agree well with and complement the findings from other studies, demonstrating that superconducting qubits can be used as a reliable tool for high-frequency characterization of dielectric materials. We conclude with a discussion of how changes in design and material choice could improve qubit lifetimes by up to a factor of 4.