On-chip GKP Quantum Error Correction with a Fluxonium Control Qubit, Part 2/2

Bosonic quantum error correction (QEC) protocols encode and protect quantum information in the phase space of a quantum harmonic oscillator, offering a hardware-efficient path towards fault-tolerant quantum computing. To control the encoded information, a nonlinear element, such as a qubit, is coupled to the harmonic oscillator. With superconducting circuits, bosonic QEC has been achieved within the high-Q harmonic mode of a 3D microwave cavity dispersively coupled to a fixed-frequency transmon qubit. However, all previous demonstrations have been limited by bit-flips in the transmon control qubit and have been performed in 3D cavity architectures. We instead use a heavy fluxonium as a control qubit which can offer improved bit-flip lifetimes, coupled to a thousand-times smaller coplanar waveguide resonator in an extensible 2D architecture. Moreover, by tuning an external flux bias, we can decouple the fluxonium and harmonic oscillator in-situ to prevent backaction on the encoded information during parts of the error correction protocol. In this second part of a two-part talk, we will share results on the creation, stabilization, and manipulation of a Gottesman-Kitaev-Preskill qubit in our planar architecture.