Introduction to Quantum-limited Parametric Amplification of Quantum Signals with Josephson Circuits

TL;DR

This paper reviews quantum-limited parametric amplification using Josephson circuits, emphasizing the principles, nonlinearities, and key characteristics of these amplifiers for microwave quantum signals.

Contribution

It provides an overview of the fundamental principles and characteristics of Josephson-based parametric amplifiers, highlighting their quantum-limited performance and design considerations.

Findings

Amplifiers operate near quantum limit for noise.

Dispersive nonlinearity of Josephson junctions enables amplification.

Key characteristics include mode structure and port configuration.

Abstract

This short and opinionated review starts with a concept of quantum signals at microwave frequencies and focuses on the principle of linear parametric amplification. The amplification process arises from the dispersive nonlinearity of Josephson junctions driven with appropriate tones. We discuss two defining characteristics of these amplifiers: the number of modes receiving the signal, idler and pump waves and the number of independent ports through which these waves enter into the circuit.