Programmable Parametric Resonator with Independent G-SNAIL-based Modulation

Descripción del proyecto

Mejora de la precisión en los circuitos de computación cuántica

En los circuitos superconductores, la generación de estados arbitrarios de variable continua requiere modular la excitación del cúbit o del resonador. Sin embargo, la no linealidad de Kerr inherente a la cavidad limita esta técnica convencional, ya que distorsiona los estados y reduce la precisión de las operaciones. El proyecto PPRISM-G, respaldado por las acciones Marie Skłodowska-Curie, tiene por objeto superar esta limitación mediante el desarrollo de un resonador paramétrico programable. El dispositivo incorporará una modulación gradiométrica independiente mediante un elemento inductivo asimétrico no lineal superconductor (G-SNAIL), con el fin de lograr una lectura de cúbits altamente ajustable y con bajo nivel de ruido para la computación cuántica. Entre los principales objetivos figuran construir el resonador G-SNAIL, evaluar su capacidad de reconfiguración mediante la caracterización del coeficiente de Kerr y validar su rendimiento mediante la generación de estados no gaussianos y el control universal de modos de variable continua.

Objetivo

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.