Superconducting Quantum Routers, Modules, Gates, and Measurements Based on Charge-pumped Parametric Interactions

Abstract: Precisely controlled couplings between qubits are vital parts of all quantum information processing. While most superconducting qubits use the "surface code" structure, which involves two-body interactions on a 2D lattice, longer-range and multi-node couplings offer efficiency and innovative error correction. In my PhD research, I have been working on realizing such qubit connections via three-wave parametric interactions and using them to build modular quantum computers.  We have realized two components of a large-scale modular machine: a quantum state router with all-to-all couplings among four simple modules, and a compact 4-qubit quantum module. Both systems are designed around the idea of coupling multiple computational modes to a central Superconducting Nonlinear Asymmetric Inductive eLement (SNAIL) and are fully controlled with 3-wave-mixing parametric interactions. I will present experiment results measured in both systems, including fast all-to-all gates between arbitrary module cavity pairs, high-fidelity single and multi-qubit parametric gates, and inter/intra-module qubit entanglement. The operations demonstrated here can readily be extended to faster and higher-fidelity parametric operations, as well as scaled to support larger networks of modular quantum computers. Moreover, I’ll also discuss control electronics development to enable these experiments and other usages of multi-parametric interactions, for example in quantum measurement.