Traveling wave parametric amplifiers for microwave quantum optics (PART II)*

Traveling wave parametric amplifiers (TWPAs) have proven to be key tools to realize broadband amplification near the quantum limit. However, their range of application is not limited to signal amplification. They are even promising candidates for multi-mode entanglement generation to realize quantum optics experiments in the microwave regime. In this context, one quickly reaches parameter regimes where higher harmonics of the pump field build up and influence the device performance crucially. Hence, a theoretical description capturing the impact of these higher harmonics becomes indispensable. To study the influence of these higher harmonics, we extend the standard description of signal and idler mode dynamics in the TWPA accordingly. Based on our model we explore the effects of higher harmonics on gain, noise and entanglement characteristics, and compare our results to experimental data.