A Near Quantum Limited Sub-GHz TiN Kinetic Inductance Traveling Wave Parametric Amplifier Operating in a Frequency Translating Mode

  1. Farzad Faramarzi,
  2. Sasha Sypkens,
  3. Ryan Stephenson,
  4. Byeong H. Eom,
  5. Henry Leduc,
  6. Saptarshi Chaudhuri,
  7. and Peter Day
We present the design and experimental characterization of a kinetic-inductance traveling-wave parametric amplifier (KI-TWPA) for sub-GHz frequencies. KI-TWPAs amplify signals through
nonlinear mixing processes supported by the nonlinear kinetic inductance of a superconducting transmission line. The device described here utilizes a compactly meandered TiN microstrip transmission line to achieve the length needed to amplify sub-GHz signals. It is operated in a frequency translating mode where the amplified signal tone is terminated at the output of the amplifier, and the idler tone at approximately 2.5~GHz is brought out of the cryostat. By varying the pump frequency, a gain of up to 22 dB was achieved in a tunable range from about 450 to 850~MHz. Use of TiN as the nonlinear element allows for a reduction of the required pump power by roughly an order of magnitude relative to NbTiN, which has been used for previous KI-TWPA implementations. This amplifier has the potential to enable high-sensitivity and high-speed measurements in a wide range of applications, such as quantum computing, astrophysics, and dark matter detection.

A 4-8 GHz Kinetic Inductance Travelling-Wave Parametric Amplifier Using Four-Wave Mixing with Near Quantum-Limit Noise Performance

  1. Farzad Faramarzi,
  2. Ryan Stephenson,
  3. Sasha Sypkens,
  4. Byeong H. Eom,
  5. Henry LeDuc,
  6. and Peter Day
Kinetic inductance traveling-wave parametric amplifiers (KI-TWPA) have a wide instantaneous bandwidth with near quantum-limited sensitivity and a relatively high dynamic range. Because
of this, they are suitable readout devices for cryogenic detectors and superconducting qubits and have a variety of applications in quantum sensing. This work discusses the design, fabrication, and performance of a KI-TWPA based on four-wave mixing in a NbTiN microstrip transmission line. This device amplifies a signal band from 4 to 8~GHz without contamination from image tones, which are produced in a separate higher frequency band. The 4 – 8~GHz band is commonly used to read out cryogenic detectors, such as microwave kinetic inductance detectors (MKIDs) and Josephson junction-based qubits. We report a measured maximum gain of over 20 dB using four-wave mixing with a 1-dB gain compression point of -58 dBm at 15 dB of gain over that band. The bandwidth and peak gain are tunable by adjusting the pump-tone frequency and power. Using a Y-factor method, we measure an amplifier-added noise of 0.5≤Nadded≤1.5 photons from 4.5 – 8 GHz.

Plasma-enhanced atomic layer deposition of titanium nitride for superconducting devices

  1. John Femi-Oyetoro,
  2. Sasha Sypkens,
  3. Henry LeDuc,
  4. Matthew Dickie,
  5. Andrew Beyer,
  6. Peter Day,
  7. and Frank Greer
This study presents a comprehensive investigation into the exceptional superconducting attributes of titanium nitride (TiN) achieved through plasma-enhanced atomic layer deposition
(PEALD) on both planar and intricate three-dimensional (3D) structures. We introduced an additional substrate biasing cycle to densify the film and remove ligand residues, augmenting the properties while minimizing impurities. While reactive-sputtered TiN films exhibit high quality, our technique ensures superior uniformity by consistently maintaining a desired sheet resistance greater than 95 percent across a 6inch wafer, a critical aspect for fabricating extensive arrays of superconducting devices and optimizing wafer yield. Moreover, our films demonstrate exceptional similarity to conventional reactive-sputtered films, consistently reaching a critical temperature (Tc) of 4.35 K with a thickness of around 40 nm. This marks a notable achievement compared to previously reported ALD-based superconducting TiN. Using the same process as for planar films, we obtained Tc for aspect ratios (ARs) ranging from 2 to 40, observing a Tc of approximately 2 K for ARs between 2 and 10.5. We elucidate the mechanisms contributing to the limitations and degradation of superconducting properties over these aggressive 3D structures. Our results seamlessly align with both current and next-generation superconducting technologies, meeting stringent criteria for thin-film constraints, large-scale deposition, conformality, 3D integration schemes, and yield optimization.

Demonstration of a Quantum Noise Limited Traveling-Wave Parametric Amplifier

  1. Nikita Klimovich,
  2. Peter Day,
  3. Shibo Shu,
  4. Byeong Ho Eom,
  5. Jenry Leduc,
  6. and Andrew Beyer
Recent progress in quantum computing and the development of novel detector technologies for astrophysics is driving the need for high-gain, broadband, and quantum-limited amplifiers.
We present a purely traveling-wave parametric amplifier (TWPA) using an inverted NbTiN microstrip and amorphous Silicon dielectric. Through dispersion engineering, we are able to obtain 50 Ω impedance matching and suppress undesired parametric processes while phase matching the three-wave-mixing amplification across a large range of frequencies. The result is a broadband amplifier operating with 20 dB gain and quantum-limited noise performance at 20 mK. At the single frequency where the amplifier is phase sensitive, we further demonstrate 8 dB of vacuum noise squeezing.