发表机构
Chalmers University of Technology（查尔姆斯理工大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过扩展能隙工程设计出铌基磁通可调 transmon，大幅提升了超导量子比特对近红外光场的鲁棒性，抑制了准粒子诱导的弛豫与频率偏移。
AI 中文摘要
超导量子电路是大规模量子处理器的基础，且正日益与光学系统结合，但它们易受高能辐射和光场导致的准粒子中毒影响。约瑟夫森结的能隙工程可抑制准粒子诱导的弛豫，但结附近的准粒子仍会改变量子比特频率并引发相位误差。本文中，我们将能隙工程扩展至结之外，采用带有金-铌接地平面和岛的磁通可调 transmon，以及强能隙工程的铝结，旨在使准粒子远离结引线。与标称结相同的全铝 transmon 相比，我们证明铌器件在 excess 弛豫出现前可承受高一个数量级以上的近红外光功率。在相同功率范围内，Nb transmon 未显示可分辨的准粒子诱导频率偏移。同时，即使弛豫仍受保护，我们仍观察到退相和态制备与测量保真度随光功率增加。这些结果表明，对结之外的准粒子能谱进行工程设计可显著提高量子比特的鲁棒性，不仅能抵御辐射诱导的错误突发，还能抵御附近的光场。
英文摘要
Superconducting quantum circuits underpin large-scale quantum processors and are increasingly interfaced with optical systems, yet they are vulnerable to quasiparticle poisoning from high-energy radiation and optical fields. Gap engineering of Josephson junctions suppresses quasiparticle-induced relaxation, but quasiparticles near the junction can still shift the qubit frequency and cause phase errors. Here, we extend gap engineering beyond the junction using a flux-tunable transmon with a gold-on-niobium ground plane and island and strongly gap-engineered aluminum junctions designed to keep quasiparticles away from the junction leads. Compared with an all-aluminum transmon with nominally identical junctions, we demonstrate that the niobium device withstands more than an order of magnitude higher near-infrared optical power before excess relaxation appears. The Nb transmon shows no resolvable quasiparticle-induced frequency shift over the same power range. At the same time, we observe that dephasing and state-preparation-and-measurement infidelity increase with optical power even while relaxation remains protected. These results suggest that engineering the quasiparticle energy landscape beyond the junction can substantially increase qubit resilience, not only to radiation-induced error bursts, but also to nearby optical fields.
Comments13 pages, 9 figures
