三维传输子量子比特的退相干参数表征

超导量子比特的退相干时间是决定超导量子计算能否实现的重要指标之一. 文章以三维传输子量子比特(3D transmon)为研究对象, 在氧化硅衬底上制备了三维传输子量子比特, 并在超低温下(10 mK), 采用拉比振荡(Rabi oscillation)、能量弛豫(energy relaxation)、 拉姆齐条纹(Ramsey fringe)、自旋回波(spin echo)的方法, 对其进行了详细的退相干时间常数表征. 结果显示该量子比特的退相干时间在几百纳秒. 根据几种退相干时间的关系进行计算, 可以看出, 低频噪声目前不是影响量子比特退相干的最主要因素, 而氧化硅中的缺陷可能是样品退相干时间的主要瓶颈. 关键词： 三维传输子量子比特 拉比振荡 拉姆齐条纹 自旋回波

Decoherence characterization of three-dimensional transmon

The decoherence time of superconducting qubit is one of the main parameters that determine whether superconducting quantum computation can be realized. This paper mainly focuses on three-dimensional (3D) transmon. The sample is fabricated on SiO substrate, and measured in 10 mK temperature. By measuring Rabi oscillation, energy relaxation, Ramsey oscillation and spin echo, the decoherence time constants of 3D transmon are characterized. The results show that the decoherence time is around several hundred nanoseconds. Based on the relationship of different decoherence time constant, we have the concludes that the possible reason to diminish the decoherence time is the defect in SiO substrate, but not the low frequency noises.
Keywords： 3D transmon Rabi oscillation Ramsey fringe spin echo