Flux 泵浦 Kerr 无参数放大器

我们提出一种基于对称ly threaded superconducting quantum interference devices (SQUIDs) 的 flux-pumped 超导参量放大器，通过 suitable drive conditions 实现 Kerr-free operating point。消除 Kerr 非线性对于 quantum-limited 放大至关重要，因为它 can mitigate unwanted distortions in squeezing and prevent degradation of both gain and quantum efficiency in the high-gain strong drive regime。通过将对称ly threaded SQUIDs (STS) 配置中的 central junction 替换为 linear inductor，我们发现 Kerr-非线性 can be eliminated and effective Hamiltonian reduces to degenerate parametric amplifier (DPA) 的形式，仅在 superconducting phase operator zero-point fluctuations 的 higher-order 修正项中存在差异。我们表明，这些 higher-order 项引入的 deviation from ideal DPA behavior 显著弱于 Kerr 非线性 所致的 deviation。Consequently，STS 设计可在 near-quantum-limited performance at the Kerr-free point 下 strong drive，实现 phase-preserving gain and efficiency 接近 quantum limit，robust operation demonstrated up to 25 dB of gain。