Low Power Inductance Traveling Wave Parametric amplifier for detectors and qubits readout*

A Kinetic Inductance Traveling Wave amplifier (KIT) utilizes the nonlinear kinetic inductance of superconducting films, particularly Niobium Titanium Nitride (NbTiN), for parametric amplification, achieving remarkable performance in terms of gain, bandwidth, compression powers, and approaching the quantum limit for noise. At millikelvin temperatures, KIT working in 3-wave-mixing (3WM) and fabricated from a 20 nm thick NbTiN film have shown to operate close to the quantum limit [1]. However, they still require fairly high pump power, and the pump must be isolated from the device under test by components that unavoidably add insertion loss, thereby degrading the system noise of the chain. To address this, we have initiated efforts to reduce the pump power by using thinner NbTiN films that show higher kinetic sheet inductance [2], and an inverted microstrip transmission line design. In this contribution, we present the new proposed line design, the fabrication procedure and initial device characterization, including gain and added noise. These measurements indicate that high gain (> 20 dB) across a broad bandwidth (a few GHz) with noise levels approaching the quantum limit can be achieved using lower pump power and reduced DC bias. These promising results pave the way for the utilization of KIT amplifiers in the readout of arrays of detectors and qubits.

[1] M. Malnou et al. PRX Quantum 2 (2021) 010302

[2] A. Giachero et al. IEEE Trans. Appl. Supercond. 33(5) (2023) 1700905