Superconducting Quantum Routers, Modules, Gates, and Measurements Based on Charge-pumped Parametric InteractionsZhou, Chao (2024) Superconducting Quantum Routers, Modules, Gates, and Measurements Based on Charge-pumped Parametric Interactions. Doctoral Dissertation, University of Pittsburgh. (Unpublished)
AbstractSuperconducting quantum circuits have emerged as very promising platforms for quantum information processing. As the field navigates the Noisy Intermediate-Scale Quantum era, we can now achieve high-fidelity quantum gates across hundreds of physical qubits. Nonetheless, evolving from NISQ machines to fault-tolerant quantum computers still requires numerous advancements in both science and engineering. In this dissertation, I aim to contribute solutions to the challenge of realizing large-scale quantum computers by exploring new ways to employ parametric interactions in superconducting quantum circuits. Specifically, the parametric charge-pumping scheme, activated by directly applying microwave drives to a coupler device that is coupled to one or multiple fixed frequency qubits, offers the versatility to execute a variety of both single-qubit and multi-qubit quantum operations. Moreover, the parametric coupling scheme also facilitates innovative qubit connection architectures and potential new error correction schemes. The thesis starts with an introduction to the theory of charge-pumped parametric interactions and the classical electronics setup necessary for such operations. Building on this foundation, I showcase the potential of parametric interactions using two experimental works conducted during my PhD. Firstly, we have realized a prototype modular structure superconducting quantum computer with parametric interactions. The design centrals a microwave quantum state router that realizes all-to-all couplings among four independent and detachable quantum modules. We have performed full mode characterization, gate calibration, inter- and intra-module photon transfer, pairwise entanglements, and even parallel operation of simultaneous iSWAP gates. This experiment illustrates the potential of parametric interactions for building high-efficiency qubit inter-connections. Secondly, I demonstrate the versatility of parametric interactions by performing a parametric transverse component readout on a transmon qubit. This experiment utilizes the idea of `multi-parametric interactions', in which multiple parametric drives are applied simultaneously to a set of quantum modes, and shows that a three-wave mixing coupler device can not only be used for quantum gates, but can also be used to perform novel qubit readouts that can be potentially very useful in qubit error correction schemes. In the concluding chapter, I discuss the future of the parametric coupling scheme in larger-scale modular devices and ongoing efforts to enhance parametric coupler performance. Share
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