Single-mode Grid-Code Operations Approaching 1% Logical Errors, Part 2: Experiments

Grid codes in superconducting circuit architectures represent a resource-efficient platform to robustly encode quantum information enabling quantum error correction [1,2]. For computation, high fidelity single-mode operations are of paramount importance to ensure reliable control at large scale.

Here, we present a full benchmark on a single-mode grid code qubit, from state preparation to stabilization, gates and logical measurements, approaching 1% errors across all operations. To reach this low error rate, we present the first experimental results of improved state preparation in a repeat-until-success approach, via post-selected stabilization [3] starting from either vacuum or squeezed states. We leverage the universal control and reset of the transmon auxiliary qubit and echoed conditional displacement gate to autonomously stabilize and perform gates on the GKP qubit. Finally, we demonstrate the reduction of SPAM errors through repeated finite-energy measurements.

[1] M. Lemonde et al., arXiv : 2409.05813 (2024)

[2] D. Lachance-Quirion et al., Phys. Rev. Lett. 132, 150607 (2024)

[3] B. Royer, S. Singh, and S. M. Girvin, Phys. Rev. Lett. 125, 260509 (2020)