Preliminary characterisation of titanium nitride thin film at 300 mK for the development of kinetic inductance travelling wave parametric amplifiers

Abstract

Travelling wave parametric amplifiers (TWPAs) made from highly nonlinear reactive superconducting thin films have been demonstrated to be a viable technology for various quantum applications, including fundamental physics experiments such as astronomy and axion dark matter searches, as well as commercial applications like quantum computational and communication systems. In this paper, we present the design of a kinetic inductance TWPA comprising a patterned titanium nitride film that can operate at 0.3 K to demonstrate the feasibility of operation closer to 1 K temperature, paving the way to achieve even higher bath temperature operation. We discuss in detail the design of our TWPA, along with the predicted gain-bandwidth product and other characteristics. We perform the preliminary experimental investigation of the thin film properties and compare that with the simulated results. We found that there are several discrepancies between the measured and the predicted behaviour of the thin film. We attribute these differences to the fact that the fabricated thin film has a different gap voltage, resistivity and thickness to what we expected. With a new set of estimated parameters, we successfully reproduce the measured transmission profile. We further show that by utilising bridges to ensure equipotential grounds for the CPW lines, we managed to reduce the rippling effect and achieve higher gain with broader bandwidth. We expect that our TWPA can achieve higher than 20 dB gain from approximately 0-8 GHz.

Balanced travelling-wave parametric amplifiers for practical applications

“…Periodic impedance loadings are made to the transmission line every 460 μm to achieve the desired dispersion engineering, and the designed pump frequency is 6.41 GHz. Full details of the KITWPA device are presented in [32]. The transmission and gain performance are simulated using the rigorous modelling technique described in [22], and are presented in figure 4.…”

Non-degenerate-pump four-wave mixing kinetic inductance travelling-wave parametric amplifiers

“…Additionally, the design simplicity is countered by the fact that the strong pump tone at the centre of the gain profile must be removed before the subsequent signal processing chain in order to prevent saturation of the microwave components following the KITWPA, such as the cryogenic low-noise amplifiers (LNAs). For example, in actual operation of a KITWPA, one needs to utilise a separate, phase-shifted pump tone to eliminate the original pump, which demands additional RF components [16] and takes up valuable space in a cryogenic environment. This solution may also incur additional unwanted losses in the detection chain, not to mention complicating the experimental setup.…”

Engineering the thin film characteristics for optimal performance of superconducting kinetic inductance amplifiers using a rigorous modelling technique

“…TWPAs achieve broadband amplification by unfolding the nonlinear medium into a long transmission wire, thereby lifting the limitation imposed by the cavity. The source of the wire’s nonlinearity can be induced by either utilising the kinetic inductance of a superconducting wire (KITWPA) 7 , 16 , 20 – 28 or with a series of Josephson junctions (JTWPAs) embedded along the wire 8 , 29 – 35 .…”