Peter K. Day

Magnetic-Field and Temperature Limits of a Kinetic-Inductance Traveling-Wave Parametric Amplifier

  1. Lucas M. Janssen,
  2. Farzad Faramarzi,
  3. Henry G. LeDuc,
  4. Sahil Patel,
  5. Gianluigi Catelani,
  6. Peter K. Day,
  7. Yoichi Ando,
  8. and Christian Dickel
Kinetic-inductance traveling-wave parametric amplifiers (KI-TWPAs) offer broadband near-quantum-limited amplification with high saturation power. Due to the high critical magnetic fields
of high-kinetic-inductance materials, KI-TWPAs should be resilient to magnetic fields. In this work, we study how magnetic field and temperature affect the performance of a KI-TWPA based on a thin-NbTiN inverse microstrip with a Nb ground plane. This KI-TWPA can provide substantial signal-to-noise ratio improvement (ΔSNR) up to in-plane magnetic fields of 0.35T and out-of-plane fields of 50mT, considerably higher than what has been demonstrated with TWPAs based on Josephson junctions. The field compatibility can be further improved by incorporating vortex traps and by using materials with higher critical fields. We also find that the gain does not degrade when the temperature is raised to 3K (limited by the Nb ground plane) while ΔSNR decreases with temperature consistently with expectation. This demonstrates that KI-TWPAs can be used in experiments that need to be performed at relatively high temperatures. The operability of KI-TWPAs in high magnetic field opens the door to a wide range of applications in spin qubits, spin ensembles, topological qubits, low-power NMR, and the search for axion dark matter.
arxiv pdf

Design of a W-band Superconducting Kinetic Inductance Qubit (Kineticon)

  1. Farzad B. Faramarzi,
  2. Peter K. Day,
  3. Marco Colangelo,
  4. Jacob Glasby,
  5. Sasha Sypkens,
  6. Ralph Chamberlin,
  7. Kevin O'Brian,
  8. Mohammad Mirhosseini,
  9. Kevin Schmidt,
  10. Karl Berggren,
  11. and Philip Mauskopf
Superconducting qubits are widely used in quantum computing research and industry. We describe a superconducting kinetic inductance qubit (Kineticon) operating at W-band frequencies
with a nonlinear nanowire section that provides the anharmonicity required for two distinct quantum energy states. Operating the qubits at higher frequencies relaxes the dilution refrigerator temperature requirements for these devices and paves the path for multiplexing a large number of qubits. Millimeter-wave operation requires superconductors with relatively high Tc, which implies high gap frequency, 2Δ/h, beyond which photons break Cooper pairs. For example, NbTiN with Tc=16K has a gap frequency near 1.4 THz, which is much higher than that of aluminum (90 GHz), allowing for operation throughout the millimeter-wave band. Here we describe a design and simulation of a W-band Kineticon qubit embedded in a 3-D cavity.
arxiv pdf