The remarkable advances of quantum computation technology with superconducting qubits based on circuit quantum electrodynamics (QED) architecture have been achieved by improving control, protection and measurement of the quantum states at the same time. At the heart of all these quantum operations, the significant enhancement of the qubit coherence time during the last decades was the key. Even after all these advances, the coherence and relaxation time of superconducting qubits still requires further improvements toward fault-tolerant quantum computation. Here, we report our observation of a strongly enhanced lifetime of an in-situ tunable superconducting transmon qubit on a silicon substrate that is embedded in a three-dimensional copper cavity. We measured a lifetime of the qubit of up to 84 µs, which is the best reported value of an in-situ tunable transmon on a silicon substrate. In our experiment, the in-situ frequency tunability over a broad range enabled the Purcell factor to be controlled continuously by detuning the qubit frequency against the resonator frequency in the strong dispersive regime. The silicon substrate has its own importance because the substrate should be fully compatible with the conventional semiconductor processes so that scalability and multi-chip module capability are guaranteed. In order to control the Purcell factor with another parameter, we displaced the qubit position in the cavity and observed a longer relaxation time with a smaller coupling coefficient. We believe that this systematic study and the control technique of the Purcell effect in the circuit QED design, together with minimizing the microwave photon loss through an improvement of the fabrication, will contribute to the realization of a practical large-scale quantum computer based on superconducting qubit technology.

中文翻译：

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观察到硅衬底上原位可调谐晶体管的强增强弛豫时间达到接近 100 μs 的 Purcell 极限

通过同时改进对量子态的控制、保护和测量，实现了基于电路量子电动力学（QED）架构的超导量子位量子计算技术的显着进步。在所有这些量子操作的核心，过去几十年量子位相干时间的显着增强是关键。即使在所有这些进步之后，超导量子位的相干性和弛豫时间仍然需要进一步改进以实现容错量子计算。在这里，我们报告了我们对嵌入在三维铜腔中的硅衬底上的原位可调谐超导超导量子位的显着增强寿命的观察。我们测量了高达 84 µs 的量子位寿命，这是硅衬底上原位可调谐晶体管的最佳报道值。在我们的实验中，在较宽范围内的原位频率可调性使珀塞尔因子能够通过在强色散状态下相对于谐振器频率去调谐量子位频率来连续控制。硅衬底有其自身的重要性，因为衬底应该与传统的半导体工艺完全兼容，从而保证可扩展性和多芯片模块能力。为了用另一个参数控制珀塞尔因子，我们移动了腔中的量子位位置，并观察到更长的弛豫时间和更小的耦合系数。我们认为，这种系统的研究和电路 QED 设计中的珀塞尔效应控制技术，