Figure 5From: Negative-resistance models for parametrically flux-pumped superconducting quantum interference devicesThis figure depicts the equivalent signal impedance of the flux-pumped SQUID in the three-wave nondegenerate case. The constituent inductances are given by Eq. (66). In the limit that the ac-flux is small such that γ 0 ≈1, the inductance L n , 0 is simply the quiescent Josephson inductance and L n , 2 ∝ Φ ac 2 . The L n , 2 acquires an imaginary component due to the external (real) admittance at the idler frequency. A positive, imaginary inductance is a negative, real impedance, which may therefore provide gain.Back to article page