Bosonic Quantum Error Correction with a Heavy Fluxonium Control Qubit

Abstract

Bosonic codes store information in the phase space of a quantum harmonic oscillator and offer a hardware‐efficient path towards quantum error correction (QEC), requiring only an oscillator and an auxiliary qubit for measurement and universal control. Of the many bosonic codes, the so‐called Gottesman‐Kitaev‐Preskill (GKP) code stands out as one of the most robust to dominant physical decoherence mechanisms, but is severely limited by bit‐ flip errors in the control qubit. In this thesis, we develop a new approach for implementing GKP QEC in superconducting circuits based on using a heavy fluxonium as the auxiliary control qubit due to its inherent bit‐flip protection. We demonstrate progress towards this in experiment by using a fluxonium in a 3D superconducting cavity architecture, and also propose novel strategies for moving future experiments to a fully 2D platform.