Superconducting Circuits for Noise-Resilient Qubits

Quantum computers are fundamentally limited by interactions with their environment. In superconducting quantum processors, microscopic degrees of freedom such as quasiparticle excitations and charge- or flux-coupled defects couple to the qubit circuits, inducing noise and therefore decoherence.
In this talk, I will give an overview of the operating principles of superconducting qubits, how specific noise processes induce decoherence in these systems, and how, in principle, qubit circuits could be designed such that the qubit manifold is protected from these decoherence channels. I will then discuss our recent proposal for a new noise-resilient qubit that we have nick-named “harmonium” (arXiv 2502.15459). I will explain how the harmonium circuit imbues the qubit with enhanced bit- and phase-flip protection, and how we can perform gates and readout.