Amplification with an array of lumped Josephson Parametric Converters

Josephson Parametric Amplifiers, although nearly quantum-limited, suffer from lack of directionality, low saturation powers, and a fixed gain-bandwidth product. We have recently shown that when extremely strong, carefully imbalanced gain and conversion processes (GCI) are combined between a pair of modes, we produce an amplifier that has broadband, bi-directional gain in transmission and is matched at both ports. This latter feature opens the possibility of chaining GCI amplifiers together in series. We have realized an amplifier series array by chaining two Josephson Parametric Converters (JPCs) together in such a way that signal ports form the chain’s input and output and the two idlers are matched in frequency and capacitively coupled. The signal modes have deliberately different frequencies so that all parametric processes may be individually controlled. As the dynamic range of JPCs typically fall faster than linearly with gain, we can distribute gain unequally among the array elements to enhance the array’s overall saturation power. We will also use our array as a platform for studying new combinations of parametric couplings, with a particular focus on pump schemes which provide directional amplification.
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