Programmable Parametric Resonator with Independent G-SNAIL-based Modulation

Description du projet

Améliorer la précision des circuits d’informatique quantique

Dans les circuits supraconducteurs, la création d’états à variables continues arbitraires repose traditionnellement sur la modulation du qubit, ou l’excitation du résonateur. Cette technique standard est toutefois limitée par la non-linéarité de Kerr inhérente à la cavité, qui déforme les états et restreint la précision opérationnelle. Soutenu par le programme Actions Marie Skłodowska-Curie, le projet PPRISM-G entend contourner ce goulot d’étranglement en développant un résonateur paramétrique programmable doté d’une modulation par élément inductif asymétrique non linéaire supraconducteur gradiométrique (G-SNAIL) afin d’obtenir une lecture de qubits hautement accordable et à faible bruit en informatique quantique. Les principaux objectifs du projet consistent notamment à construire le résonateur G-SNAIL, à évaluer sa reconfigurabilité par cartographie du coefficient de Kerr et à valider ses performances par la création d’états non gaussiens et le contrôle universel des modes à variables continues.

Objectif

Two paradigmatic approaches for generating arbitrary continuous-variable (CV) states in a qubit–resonator system rely on time-modulating either the qubit drive or the resonator drive. However, the intrinsic Kerr nonlinearity of superconducting cavities imposes a fundamental limit on operation fidelity. Terminating a resonator with a Superconducting Nonlinear Asymmetric Inductive eLement (SNAIL) can mitigate this limitation by providing flux-tunable third- and fourth-order nonlinearities. While the SNAIL’s nonlinear terms are tunable in general, they become fixed at the Kerr-free point, constraining control over gate strengths. This proposal develops a Programmable Parametric Resonator incorporating a Gradiometric SNAIL (G-SNAIL), which is a two-loop, symmetric extension of the SNAIL with a central Josephson junction array flanked by two smaller-critical-current junctions. In contrast to standard SNAILs, the G-SNAIL enables independent, simultaneous tuning of cubic and quartic nonlinearities with negligible frequency perturbation, preserving coherence while expanding functional versatility. This is achieved via dual-flux biasing of the loops, allowing continuous control, and sign reversal, of the Kerr coefficient through the interplay of cubic and quartic terms. The G-SNAIL-terminated resonator functions as a compact, reconfigurable nonlinearity module capable of implementing a universal set of bosonic operations within a single element, reducing hardware complexity by eliminating multiple fixed-design components. The proposed program includes: (i) design, fabrication, and spectral characterization of the G-SNAIL resonator; (ii) Kerr-coefficient mapping to quantify its reconfigurability; and (iii) benchmarking via universal CV mode control and non-Gaussian state generation. This platform paves the way for scalable, fault-tolerant CV quantum computation, with potential transformative impact on high-precision quantum sensing.