Characterization of a multimode coplanar waveguide parametric amplifier
  We characterize a novel Josephson parametric amplifier based on a flux-tunable quarter-wavelength resonator. The fundamental resonance frequency is ~1GHz, but we use higher modes of the resonator for our measurements. An on-chip tuning line allows for magnetic flux pumping of the amplifier. We investigate and compare degenerate parametric amplification, involving a single mode, and nondegenerate parametric amplification, using a pair of modes. We show that we reach quantum-limited noise performance in both cases, and we show that the added noise can be less than 0.5 added photons in the case of low gain. 
M. Simoen, C. W. S. Chang, P. Krantz, Jonas Bylander, W. Wustmann, V.   Shumeiko, P. Delsing, and C. M. Wilson
cond-mat.mes-hall