Orateur
Description
Bosonic codes offer a resource-efficient method to quantum error correction [1]. Of particular interest, autonomous correction was successfully demonstrated for cat codes [2–5], where the logical |0⟩ and |1⟩ states are coherent states of opposite amplitudes |α⟩ and | − α⟩ in a superconducting resonator with single-photon loss rates κ1 as low as possible. They correct bit-flip errors by either using the non-linearity of the oscillator or parametrically pumping couplers to produce two-photon dissipation at a rate κ2.
The bit-flip time increases exponentially with |α|^2 while the phase-flip rate only increases linearly with |α|^2. In this work, we introduce and experimentally demonstrate a new superconducting circuit designed to correct for bit-flip errors of cat codes. Crucially, the two-photon dissipation does not require any pump, so that a single drive is required to stabilize the qubit manifold. This is obtained by nonlinearly coupling the cat qubit to a buffer mode that resonates at twice the frequency of the cat qubit.
We experimentally demonstrate unprecedented ratios κ2/κ1, so that bit flip times well over a ms can be reached with a few photons only. We also demonstrate quantum gates on this corrected cat qubit.
This work was partly supported by the grant ANR-19-QUAN-0006.
[1] Z. Leghtas et al., Phys. Rev. Lett. 111, 120501 (2013). [2] R. Lescanne et al., Nature Physics 16, 509 (2020). [3] S. Touzard et al., Phys. Rev. X 8, 021005 (2018). [4] C. Berdou et al., (2022), 10.48550/ARXIV.2204.09128. [5] N.E. Frattini et al., (2022), 10.48550/ARXIV.2209.03934
