Abstract
Bosonic quantum error correction (QEC) encodes information in the phase space of a quantum harmonic oscillator and offers a hardware-efficient path towards fault-tolerant quantum information processing. With superconducting circuits, bosonic QEC using the Gottesman-Kiteav-Preskill (GKP) code has been achieved within the high-Q mode of a macroscopic 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 (with typical T1 lifetimes on the order of 100 microseconds), resulting in GKP logical lifetimes that are upper-bounded by approximately ~10T1. In this work, we instead use a heavy fluxonium as a control qubit, with bit-flip lifetimes in excess of 1 millisecond. Furthermore, we propose using a microwave-activated three-wave mixing coupler to yield faster GKP error-correction rates while suppressing inherited nonlinearity in our bosonic mode. As compared to direct dispersive coupling, this parametric coupling enables us to use a heavier, and therefore more bit-flip-protected, fluxonium qubit. With an accelerated error-correction rate, we can use a planar resonator to store logical quantum information in an extensible and fully 2D architecture. Finally, we report on experimental progress towards the creation and manipulation of Gottesman-Kitaev-Preskill states using this system.
*This research was funded in part by the Army Research Office under Award Number W911NF-23-1-0045; in part by the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, Co-design Center for Quantum Advantage (C2QA) under contract number DE-SC0012704; in part by the AWS Center for Quantum Computing; and in part under Air Force Contract No. FA8702-15-D-0001. M. H. acknowledges funding from the IC Postdoctoral Fellowship. S. R. J. and S. C. acknowledge support from the NSF Graduate Research Fellowship. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the U.S. Government.
