Engineering control and readout of superconducting qubits

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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.