Ultra High Kinetic Inductance Traveling Wave Parametric Amplifier

A Kinetic Inductance Traveling-Wave Amplifier (KIT) uses the nonlinear kinetic inductance of superconducting films—particularly Niobium Titanium Nitride (NbTiN)—to achieve high gain, wide bandwidth, and near-quantum-limited noise. Compared to conventional KIT amplifiers fabricated from 20–30 nm NbTiN films with lower kinetic inductance (7–10 pH/sq) three-wave mixing KITs made from 10 nm NbTiN films (~30 pH/sq) demonstrate true gains >25 dB with very low pump power (–45 dBm) and bias current (<1 mA), reducing power dissipation, device backaction due to residual pump leakage,  and footprint (from tens of cm to 8 cm) [1]. Combined with an inverted microstrip design, these compact amplifiers improve fabrication yield and scalability for low-noise quantum readout.

Reducing NbTiN thickness below 10 nm [2] further boosts kinetic inductance, lowering power and size even more. Films as thin as 5 nm (~100 pH/sq) enable the first Ultra-High Kinetic Inductance Traveling-Wave Amplifiers (UHKITs). Their strong nonlinearity allows extremely short devices (~1 cm) and novel slow-light structures with phase velocities ~1/1000 that of light. However, this high inductance regime complicates the microwave line response and amplifier design optimization. Here, we present the design solutions, fabrication process, and characterization results of these first UHKITs and  highlight their performance and potential applications for qubit and detector readout