Realization of modular quantum computers via parametric interactions
Precisely controlled couplings between qubits are vital parts of all quantum information processing. For superconducting qubits, most platforms employ a network of two-body interactions between nearest-neighbor qubits in a two-dimensional lattice, the so-called “surface code” structure. However, longer range and multi-node couplings are very desirable as they reduce the overhead of interactions between distant qubits and enable new topologies for alternate, hopefully more efficient, error correcting schemes. 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. I’ll also discus control electronics development to enable these experiments and other usages of multi-parametric interactions, for example in quantum measurement.