Resonators in circuit quantum electrodynamics systems naturally carry multiple modes, which may have non-negligible influence on qubit parameters and device performance. While new theories and techniques are under investigation to deal with the multi-mode effects in circuit quantum electrodynamics systems, researchers have proposed novel engineering designs featuring multi-mode resonators to achieve enhanced functionalities of superconducting quantum processors. Here, we propose multi-mode bus coupling architecture, in which superconducting qubits are coupled to multiple bus resonators to gain larger coupling strength. Applications of multi-mode bus couplers can be helpful for improving i SWAP gate fidelity and gate speed beyond the limit of single-mode scenario. The proposed multi-mode bus coupling architecture is compatible with a scalable variation of the traditional bus coupling architecture. It opens up new possibilities for realization of scalable superconducting quantum computation with circuit quantum electrodynamics systems.
To meet the specification of the qubits in our laboratory,a 0.4 kA·cm^-2 superconducting rapid single flux quantum(RSFQ) circuit was designed and successfully fabricated with an improved Nb-based self-aligned lift-off process.This circuit consists of a single-fluxquantum(SFQ) pulse generator,a Josephson transmission line(JTL) and a T-flip flop(TFF),and it acts as a frequency divider.The values of the inductors in this circuit were extracted using InductEX and the basic function of this circuit was confirmed using the simulation software WRspice before fabrication.After fabrication,the basic parameters of this circuit were measured at ~2.5 K in a Janis He-3 cryostat.This work laid the theoretical and experimental basis for the future research on the RSFQqubit control circuits.
Transmission characteristics of single and double coplanar waveguide(CPW)resonators are simulated.The crosstalk of two CPW resonators located on the same chip is observed in simulation as well as in low temperature measurement results.The crosstalk behaves as exponential attenuation versus the distance between two resonators.
We successfully designed and fabricated TES bolometers utilizing Al/Ti bilayer TESs as sensitive thermometers.To reduce the intrinsic noise level and tune the saturation power of a bolometer,the TES thermometer is placed on a suspended SiN platform which is thermally coupled to the heat bath by four long SiN beams with different geometries.The measurement results show that the detectors have background limited noise performance,with a low noise equivalent power(NEP)on the order of10-17W/Hz1/2and have a saturation power of several tens pW at a bath temperature of 320 mK.These detectors are suitable for applications in ground-based astrophysics experiments by integrating absorbers for specific wavelengths.
3D Transmon是目前已知退相干时间较长的一种超导量子比特,在超导量子计算、量子光学、腔量子电动力学等方面具有重要的应用.拉比振荡是表征量子系统退相干时间的重要方法,也是体现量子系统能够进行能级演化的基本实验.对3D Transmon进行拉比振荡测试,需要进行严格的时序控制,测试调试的过程较为繁琐.本文制备了3D Transmon样品,对其基本参数进行了测试表征,创新性地提出了一种基于网络分析仪的拉比振荡测试方法,基于该方法的测试系统搭建简单,可作为迅速验证3D Transmon是否具备量子特性的一种手段,该方法也可推广至其他量子系统进行时域特性的初步验证.
