Characterization of Added Noise and Loss Mechanisms in Superconducting Kinetic Inductance Traveling Wave Parametric Amplifiers*

Contemporary quantum technologies and fundamental physics experiments rely on amplifying and detecting extremely weak signals. As all amplifiers degrade the signal-to-noise-ratio by adding their own intrinsic noise, any amplifier which adds the minimum possible noise – referred to as the Standard Quantum Limit (SQL) – is of great value. In such settings parametric amplifiers are extremely attractive due to their ability to operate at, or very near, the SQL.  Here we present a detailed characterization of the added noise of a superconducting Kinetic Inductance Traveling Wave Parametric Amplifier (KI-TWPA or KIT) capable of operating within two quanta of the SQL over 3 GHz of bandwidth. We perform an added noise characterization as a function of the operational KIT gain using the well-known y-factor technique, and independently using an intrinsically-calibrated shot noise Josephson tunnel junction. Additionally, using a vacuum noise squeezing setup, we explore the relationship between the squeezing level and added noise to further our understanding of sources of excess noise above the SQL in KITs.