Optimal operation of a Josephson parametric amplifier for vacuum squeezing

  1. M. Malnou,
  2. D. A. Palken,
  3. Leila R. Vale,
  4. Gene C. Hilton,
  5. and K. W. Lehnert
A Josephson parametric amplifier (JPA) can create squeezed states of microwave light, lowering the noise associated with certain quantum measurements. We experimentally study how the JPA’s pump influences the phase-sensitive amplification and deamplification of a coherent tone’s amplitude when that amplitude is commensurate with vacuum fluctuations. We predict and demonstrate that by operating the JPA with a pump power greater than the value that maximizes gain, the amplifier distortion is reduced and consequently squeezing is improved. Optimizing the JPA’s operation in this fashion, we directly observe 3.87±0.03 dB of vacuum squeezing.
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