Engineering control and readout of superconducting qubits

超导量子比特是量子计算和处理应用的一个有前途的候选者。在工业和学术界广泛使用的是transmon量子比特，由一个大电容器分流的约瑟夫森结组成。这些人造原子提供了能够通过制造来调整参数的好处，并且通过耦合到超导谐振器来提供容易的读出和控制。随着超导量子比特社区展望未来，一个强有力的竞争者是磁通量子比特，它被一个大电感分流，并且对电荷波动有弹性。随着人们对氟鎓的兴趣不断增长，本项目的目标是首先优化读出参数以实现高性能测量保真度，然后通过实验实现这一目标。这个项目将是我在项目B期间完成的工作的延续，涉及数值和分析优化。目的是使用我的项目B的结果，以确定适当的参数制度，适用于实验室。改进的读出能力直接使得能够有效地表征通量鎓，这进一步提高了尽可能有效地校准通量鎓门的能力。因此，该项目的未来前景将包括高保真度门的有效校准以及在多量子位架构中实现读出和门。我们最终想回答的问题是：在通量量子比特上实现高保真操作的最佳方法是什么？此外，超导量子比特的分解需要广泛的屏蔽、衰减和滤波，以防止各种退相干源。定制的Eccosorb红外滤波器广泛应用于超导量子比特社区，但很少有研究表明它们对量子比特性能的直接影响。我们的目标是构建，表征和实现这些滤波器，最终提出最佳配置，以保护量子比特免受高频光子引起的退相干。其他关键学习目标包括但不限于学习如何设计样品，并了解运行实验所需的控制电子设备和软件。

Superconducting qubits are a promising candidate for quantum computing and processing applications. Widely used in industry and academia is the transmon qubit, composed of a Josephson junction shunted by a large capacitor. These man-made atoms offer the benefit of being able to tune parameters via fabrication and offer ease of readout and control via coupling to a superconducting resonator. As the superconducting qubit community looks towards the future, a strong contender for an alternative is the fluxonium qubit, which is instead shunted by a large inductance and is resilient to charge fluctuations. As interest in the fluxonium continues to grow, the goal of this project is to first optimize readout parameters to achieve high performance measurement fidelity, and subsequently realize this experimentally. This project will be a continuation of the work I have completed during my Project B involving numerical and analytical optimization. The aim is to use the results from my Project B in order to identify the appropriate parameter regime to apply in the laboratory. Improved readout capabilities directly enable efficient characterization of the fluxonium which further improves the ability to calibrate the fluxonium gates as efficiently as possible. Thus, the future perspectives for the project will include efficient calibration of high fidelity gates and the implementation of both readout and gates in multi-qubit architectures. We ultimately want to answer the question: What is the best approach to implement high fidelity operations on fluxonium qubits? Additionally, superconducting qubits det ups require extensive shielding, attenuation, and filtering to protect against various sources of decoherence. Custom-made Eccosorb infrared filters are widely used in the superconducting qubit community, but little work has characterized their direct impact on qubit performance. We aim to build, characterize, and implement these filters to ultimately propose the optimal configuration to protect qubits against decoherence caused by high frequency photons. Other key learning objectives include, but are not limited to, learning how to design samples and understanding the control electronics and software required to run the experiments.