Michael R. Vissers

Low-noise kinetic inductance traveling-wave amplifier using three-wave mixing

  1. Michael R. Vissers,
  2. Robert P. Erickson,
  3. Hsiang-Sheng Ku,
  4. Leila Vale,
  5. Xian Wu,
  6. Gene Hilton,
  7. and David P. Pappas
We have fabricated a wide-bandwidth, high dynamic range, low-noise cryogenic amplifier based on a superconducting kinetic inductance traveling-wave device. The device was made from
NbTiN and consisted of a long, coplanar waveguide on a silicon chip. By adding a DC current and an RF pump tone we are able to generate parametric amplification using three-wave mixing. The devices exhibit gain of more than 15 dB across an instantaneous bandwidth from 4 to 8 GHz. The total usable gain bandwidth, including both sides of the signal-idler gain region, is more than 6 GHz. The noise referred to the input of the devices approaches the quantum limit, with less than 1 photon excess noise. Compared to similarly constructed four-wave mixing amplifiers, these devices operate with the RF pump at ∼20 dB lower power and at frequencies far from the signal. This will permit easier integration into large scale qubit and detector applications.
arxiv pdf

Concentric transmon qubit featuring fast tunability and site-selective Z coupling

  1. Jochen Braumüller,
  2. Martin Sandberg,
  3. Michael R. Vissers,
  4. Andre Schneider,
  5. Steffen Schlör,
  6. Lukas Grünhaupt,
  7. Hannes Rotzinger,
  8. Michael Marthaler,
  9. Alexander Lukashenko,
  10. Amadeus Dieter,
  11. Alexey V. Ustinov,
  12. Martin Weides,
  13. and David P. Pappas
We present a planar qubit design based on a superconducting circuit that we call concentric transmon. While employing a simple fabrication process using Al evaporation and lift-off
lithography, we observe qubit lifetimes and coherence times in the order of 10us. We systematically characterize loss channels such as incoherent dielectric loss, Purcell decay and radiative losses. The implementation of a gradiometric SQUID loop allows for a fast tuning of the qubit transition frequency and therefore for full tomographic control of the quantum circuit. The presented qubit design features a passive direct Z coupling between neighboring qubits, being a pending quest in the field of quantum simulation.
arxiv pdf

Frequency-tunable Superconducting Resonators via Nonlinear Kinetic Inductance

  1. Michael R. Vissers,
  2. Johannes Hubmayr,
  3. Martin Sandberg,
  4. Saptarshi Chaudhuri,
  5. Clint Bockstiegel,
  6. and Jiansong Gao
We have designed, fabricated and tested a frequency-tunable high-Q superconducting resonator made from a niobium titanium nitride film. The frequency tunability is achieved by injecting
a DC current through a current-directing circuit into the nonlinear inductor whose kinetic inductance is current-dependent. We have demonstrated continuous tuning of the resonance frequency in a 180 MHz frequency range around 4.5 GHz while maintaining the high internal quality factor Qi>180,000. This device may serve as a tunable filter and find applications in superconducting quantum computing and measurement. It also provides a useful tool to study the nonlinear response of a superconductor. In addition, it may be developed into techniques for measurement of the complex impedance of a superconductor at its transition temperature and for readout of transition-edge sensors.
arxiv pdf

Long-lived, radiation-suppressed superconducting quantum bit in a planar geometry

  1. Martin Sandberg,
  2. Michael R. Vissers,
  3. Tom Ohki,
  4. Jiansong Gao,
  5. Jose Aumentado,
  6. Martin Weides,
  7. and David P. Pappas
We present a superconducting qubit design that is fabricated in a 2D geometry over a superconducting ground plane to enhance the lifetime. The qubit is coupled to a microstrip resonator
for readout. The circuit is fabricated on a silicon substrate using low loss, stoichiometric titanium nitride for capacitor pads and small, shadow-evaporated aluminum/aluminum-oxide junctions. We observe qubit relaxation and coherence times ($T_1$ and $T_2$) of 11.7 $pm$ 0.2 $mu$s and 8.7 $pm$ 0.3 $mu$s, respectively. Calculations show that the proximity of the superconducting plane suppresses the otherwise high radiation loss of the qubit. A significant increase in $T_1$ is projected for a reduced qubit-to-superconducting plane separation.
arxiv pdf

Identifying capacitive and inductive loss in lumped element superconducting hybrid titanium nitride/aluminum resonators

  1. Michael R. Vissers,
  2. Martin P. Weides,
  3. Jeffrey S. Kline,
  4. Martin O. Sandberg,
  5. and David P. Pappas
We present a method to systematically locate and extract capacitive and inductive losses in superconducting resonators at microwave frequencies by use of mixed-material, lumped element
devices. In these devices, ultra-low loss titanium nitride was progressively replaced with aluminum in the inter-digitated capacitor and meandered inductor elements. By measuring the power dependent loss at 50 mK as the Al-TiN fraction in each element is increased, we find that at low electric field, i.e. in the single photon limit, the loss is two level system in nature and is correlated with the amount of Al capacitance rather than the Al inductance. In the high electric field limit, the remaining loss is linearly related to the product of the Al area times its inductance and is likely due to quasiparticles generated by stray radiation. At elevated temperature, additional loss is correlated with the amount of Al in the inductance, with a power independent TiN-Al interface loss term that exponentially decreases as the temperature is reduced. The TiN-Al interface loss is vanishingly small at the 50 mK base temperature.
arxiv pdf