Engineering control and readout of superconducting qubits

超导量子位是量子计算和处理应用的有前途的候选者。 transmon 量子位在工业界和学术界广泛使用，它由一个大电容器并联的约瑟夫森结组成。这些人造原子的优点是能够通过制造来调整参数，并通过与超导谐振器的耦合提供轻松的读出和控制。随着超导量子位社区展望未来，替代品的有力竞争者是 Fluxium 量子位，它由大电感分流，并且对电荷波动具有弹性。随着人们对 Fluxium 的兴趣不断增长，该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点。该项目将是我在项目 B 期间完成的涉及数值和分析优化的工作的延续。目的是利用我的项目 B 的结果来确定适用于实验室的适当参数制度。改进的读出功能可直接实现 Fluxium 的高效表征，从而进一步提高尽可能高效地校准 Fluxium 门的能力。因此，该项目的未来前景将包括高保真门的有效校准以及多量子位架构中读出和门的实现。我们最终想要回答这个问题：在 Fluxium 量子位上实现高保真度操作的最佳方法是什么？此外，超导量子位检测需要广泛的屏蔽、衰减和过滤，以防止各种退相干源。定制的 ECcosorb 红外滤光片广泛应用于超导量子位领域，但很少有研究表明它们对量子位性能的直接影响。我们的目标是构建、表征和实现这些滤波器，以最终提出最佳配置，以保护量子位免受高频光子引起的退相干的影响。其他关键学习目标包括但不限于学习如何设计样本以及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.