Travelling wave parametric amplifiers (TWPAs) made from highly non-linear reactive superconducting thin films have been demonstrated to be a potentially viable quantum-noise-limited amplifier technology for various fundamental physics platforms, including microwave/mm/sub-mm astronomy, dark matter search experiments, neutrino mass experiments, and qubit readout. We present a kinetic inductance TWPA consisting of a patterned titanium nitride film on a sapphire substrate, which comprises a coplanar waveguide (CPW) with a continuous, smoothed periodic loading (PL) structure that modulates the characteristic impedance of the CPW in a double sinusoidal fashion. This double sinusoidal modulation creates much stronger dispersion features than a conventional PL design, which allows for phase matching and pump harmonic suppression over a much shorter transmission length, potentially leading to reduced losses. In this paper, we shall discuss in detail the design of our TWPA and present the predicted gain-bandwidth characteristics from electromagnetic simulations.
Travelling wave parametric amplifiers (TWPAs) made from highly non-linear reactive superconducting thin films have been demonstrated to be a potentially viable quantum-noise-limited amplifier technology for various fundamental physics platforms, including microwave/mm/sub-mm astronomy, dark matter search experiments, neutrino mass experiments, and qubit readout. We present a kinetic inductance TWPA consisting of a patterned titanium nitride film on a sapphire substrate, which comprises a coplanar waveguide (CPW) with a continuous, smoothed periodic loading (PL) structure that modulates the characteristic impedance of the CPW in a double sinusoidal fashion. This double sinusoidal modulation creates much stronger dispersion features than a conventional PL design, which allows for phase matching and pump harmonic suppression over a much shorter transmission length, potentially leading to reduced losses. In this paper, we shall discuss in detail the design of our TWPA and present the predicted gain-bandwidth characteristics from electromagnetic simulations.
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 0.3K to demonstrate the feasibility of operation closer to 1K 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 are able to reduce the rippling effect and achieve a higher gain with broader bandwidth. We expect that our TWPA can achieve higher than 20 dB gain from approximately 0–8 GHz.
Background Kinetic inductance travelling-wave parametric amplifiers (KITWPAs) have proven effective in achieving high gain over broad bandwidths whilst achieving near quantum-limited noise performance, properties which are extremely important for many ultra-sensitive experiments such as radio/millimetre/sub-millimetre astronomy, neutrino mass experiments, and axion dark matter searches, as well as commercial applications like quantum computational and communication systems. Methods This paper introduces the preliminary experimental exploration of an alternative KITWPA utilising thin titanium nitride (TiN) films as opposed to the conventionally used niobium titanium nitride (NbTiN) films. TiN films exhibit properties that could be advantageous for KITWPA operation, owing to its controllable critical temperature (T c) and physical robustness, hence KITWPAs fabricated from TiN films have the potential to replace NbTiN-based TWPAs for various applications, such as reducing the high pump power required to drive a NbTiN TWPA. Our TiN-based KITWPA devices were designed and fabricated with a 42 cm long coplanar waveguide transmission line patterned into a 100 nm thick TiN film, wound in a double spiral fashion to fit into a 2.2×2.2 cm chip. Results We successfully achieved broadband performance, with the best device displaying a peak averaged gain of ~5 dB with a bandwidth of ~3–13 GHz, making this one of the first broadband gain measurements of a TiN KITWPA reported in the literature. Despite this, the measured gain in all batches was lower than simulated due unexpected additional loss mechanisms. Conclusions The preliminary results presented here suggest that TiN films are suitable for KITWPA operation, although further investigation is required to improve the gain performance.
Background: Kinetic Inductance Travelling Wave Parametric Amplifiers (KITWPAs) are a new variant of superconducting amplifier that can potentially achieve high gain with quantum-limited noise performance over broad bandwidth, which is important for many ultra-sensitive experiments. In this paper, we present a novel modelling technique that can better capture the electromagnetic behaviour of a KITWPA without the translation symmetry assumption, allowing us to flexibly explore the use of more complex transmission line structures and better predict their performance. Methods: In order to design a KITWPA with optimal performance, we investigate the use of different superconducting thin film materials, and compare their pros and cons in forming a high-gain low-loss medium feasible for amplification. We establish that if the film thickness can be controlled precisely, the material used has less impact on the performance of the device, as long as it is topologically defect-free and operating within its superconducting regime. With this insight, we propose the use of Titanium Nitride (TiN) film for our KITWPA as its critical temperature can be easily altered to suit our applications. We further investigate the topological effect of different commonly used superconducting transmission line structures with the TiN film, including the effect of various non-conducting materials required to form the amplifier. Results: Both of these comprehensive studies led us to two configurations of the KITWPA: 1) A low-loss 100nm thick TiN coplanar waveguide amplifier, and 2) A compact 50nm TiN inverted microstrip amplifier. We utilise the novel modelling technique described in the first part of the paper to explore and investigate the optimal design and operational setup required to achieve high gain with the broadest bandwidth for both KITWPAs, including the effect of loss. Conclusions: Finally, we conclude the paper with the actual layout and the predicted gain-bandwidth product of our KITWPAs.
Background: Kinetic Inductance Travelling Wave Parametric Amplifiers (KITWPAs) are a variant of superconducting amplifier that can potentially achieve high gain with quantum-limited noise performance over broad bandwidth, which is important for many ultra-sensitive experiments. In this paper, we present a novel modelling technique that can better capture the electromagnetic behaviour of a KITWPA without the translation symmetry assumption, allowing us to flexibly explore the use of more complex transmission line structures and better predict their performance. Methods: In order to design a KITWPA with optimal performance, we investigate the use of different superconducting thin film materials, and compare their pros and cons in forming a high-gain low-loss medium feasible for amplification. We establish that if the film thickness can be controlled precisely, the material used has less impact on the performance of the device, as long as it is topologically defect-free and operating within its superconducting regime. With this insight, we propose the use of Titanium Nitride (TiN) film for our KITWPA as its critical temperature can be easily altered to suit our applications. We further investigate the topological effect of different commonly used superconducting transmission line structures with the TiN film, including the effect of various non-conducting materials required to form the amplifier. Results: Both of these comprehensive studies led us to two configurations of the KITWPA: 1) A low-loss 100 nm thick TiN coplanar waveguide amplifier, and 2) A compact 50 nm TiN inverted microstrip amplifier. We utilise the novel modelling technique described in the first part of the paper to explore and investigate the optimal design and operational setup required to achieve high gain with the broadest bandwidth for both KITWPAs, including the effect of loss. Conclusions: Finally, we conclude the paper with the actual layout and the predicted gain-bandwidth product of our KITWPAs.
Traveling wave parametric amplifiers (TWPAs) with added noise approaching the quantum limit have enabled highly sensitive microwave frontends for qubit readout, radio astronomy, and particle physics. These amplifiers operate by mixing a strong microwave pump wave with the signal in a nonlinear waveguide, in such a way that a fraction of the pump power is used to amplify the signal and generate a co-propagating idler wave. Conventional TWPAs rely on the inductive nonlinearity originating from the Josephson effect or kinetic inductance in thin super-conductors, restricting these devices to use cases below 4K and nonmagnetic environments. In this work, we propose a C-band TWPA where a capacitive nonlinearity is engineered in transmission lines based on the paraelectric materialSrTiO3. The nonlinear properties ofSrTiO3remain stable at much higher temperatures (20K) and in high magnetic fields. We have developed a theoretical framework for the optimal geometry ofSrTiO3-based nonlinear transmission lines to achieve phase-matched parametric processes while minimizing the required pump power. Periodically loaded coplanar-waveguide (CPW)-like structures on thin-filmSrTiO3are simulated to have 20dB of gain over 100mm of interaction, based on empirical nonlinear models ofSrTiO3. Alternative methods including slotline geometries and bulkSrTiO3are also simulated. Preliminary measurements of thin-filmSrTiO3properties and amplifiers are presented as well as plans to fabricate devices that operate near 500MHz for the Project-8 neutrino mass experiment.
We present broadband parametric amplifiers based on the kinetic inductance of superconducting NbTiN thin films in an artificial (lumped-element) transmission line architecture. We demonstrate two amplifier designs implementing different phase matching techniques: periodic impedance loading and resonator phase shifters placed periodically along the transmission line. Our design offers several advantages over previous CPW-based amplifiers, including intrinsic 50 Ω characteristic impedance, natural suppression of higher pump harmonics, lower required pump power, and shorter total trace length. Experimental realizations of both versions of the amplifiers are demonstrated. With a transmission line length of 20 cm, we have achieved gains of 15 dB over several GHz of bandwidth.