近日，美国普林斯顿大学Houck, Andrew A团队研究了二维传输量子比特的毫秒寿命和相干时间。2025年11月5日出版的《自然》杂志发表了这项成果。

材料改进是降低超导量子比特损耗与退相干效应的有效途径，因其成果能直接应用于大规模处理器制造。近期研究通过采用钽作基底、蓝宝石作衬底，提升了传输子量子比特的相干性。这类器件的损耗主要源于表面与体介电质中贡献相当的双能级系统，表明必须同步改善两者才能实现技术水平的实质突破。

研究组通过采用高阻硅衬底显著降低了体衬底损耗，在45个二维传输子量子比特中实现了平均质量因子（Q^avg）达9.7×10⁶的性能。最优异量子比特的Q^avg达1.5×10⁷，最高值达2.5×10⁷，对应寿命（T₁）达1.68毫秒。低损耗特性使研究组能够观测约瑟夫森结相关的退相干效应，并通过改进低污染结沉积工艺实现哈恩回波相干时间（T_2E）超越能量弛豫时间。这些材料突破无需改变量子比特结构，可直接兼容标准量子控制门操作。研究组实现了保真度达99.994%的单量子比特门。这种钽-硅材料平台构成简洁的堆叠结构，具备晶圆级规模化制造潜力，为大规模量子处理器的开发铺平道路。

附：英文原文

Title: Millisecond lifetimes and coherence times in 2D transmon qubits

Author: Bland, Matthew P., Bahrami, Faranak, Martinez, Jeronimo G. C., Prestegaard, Paal H., Smitham, Basil M., Joshi, Atharv, Hedrick, Elizabeth, Kumar, Shashwat, Yang, Ambrose, Pakpour-Tabrizi, Alexander C., Jindal, Apoorv, Chang, Ray D., Cheng, Guangming, Yao, Nan, Cava, Robert J., de Leon, Nathalie P., Houck, Andrew A.

Issue&Volume: 2025-11-05

Abstract: Materials improvement is a powerful approach to reducing loss and decoherence in superconducting qubits, because such improvements can be readily translated to large-scale processors. Recent work improved transmon coherence by using tantalum as a base layer and sapphire as a substrate1. The losses in these devices are dominated by two-level systems with comparable contributions from both the surface and bulk dielectrics2, indicating that both must be tackled to achieve substantial improvements in the state of the art. Here we show that replacing the substrate with high-resistivity silicon markedly decreases the bulk substrate loss, enabling 2D transmons with time-averaged quality factors (Qavg) of 9.7×106 across 45qubits. For our best qubit, we achieve a Qavg of 1.5×107, reaching a maximum Q of 2.5×107, corresponding to a lifetime (T1) up to 1.68ms. This low loss also allows us to observe decoherence effects related to the Josephson junction, and we use an improved, low-contamination junction deposition to achieve Hahn echo coherence times (T2E) exceeding T1. We achieve these materials improvements without any modifications to the qubit architecture, allowing us to readily incorporate standard quantum control gates. We demonstrate single-qubit gates with 99.994% fidelity. The tantalum-on-silicon platform comprises a simple material stack that can potentially be fabricated at the wafer scale and therefore can be readily translated to large-scale quantum processors.

DOI: 10.1038/s41586-025-09687-4

Source: https://www.nature.com/articles/s41586-025-09687-4