Jan Nicolas Voss

Random telegraph fluctuations in granular microwave resonators

  1. Maximilian Kristen,
  2. Jan Nicolas Voss,
  3. Micha Wildermuth,
  4. Hannes Rotzinger,
  5. and Alexey V. Ustinov
Microwave circuit electrodynamics of disordered superconductors is a very active research topic spawning a wide range of experiments and applications. For compact superconducting circuit
elements, the transition to an insulating state poses a limit to the maximum attainable kinetic inductance. It is therefore vital to study the fundamental noise properties of thin films close to this transition, particularly in situations where a good coherence and temporal stability is required. In this paper, we present measurements on superconducting granular aluminum microwave resonators with high normal state resistances, where the influence of the superconductor to insulator phase transition is visible. We trace fluctuations of the fundamental resonance frequency and observe, in addition to a 1/f noise pattern, a distinct excess noise, reminiscent of a random telegraph signal. The excess noise shows a strong dependency on the resistivity of the films as well as the sample temperature, but not on the applied microwave power.
arxiv pdf

Rabi oscillations in a superconducting nanowire circuit

  1. Yannick Schön,
  2. Jan Nicolas Voss,
  3. Micha Wildermuth,
  4. Andre Schneider,
  5. Sebastian T. Skacel,
  6. Martin P. Weides,
  7. Jared H. Cole,
  8. Hannes Rotzinger,
  9. and Alexey V. Ustinov
We investigate the circuit quantum electrodynamics of superconducting nanowire oscillators. The sample circuit consists of a capacitively shunted nanowire with a width of about 20 nm
and a varying length up to 350 nm, capacitively coupled to an on-chip resonator. By applying microwave pulses we observe Rabi oscillations, measure coherence times and the anharmonicity of the circuit. Despite the very compact design, simple top-down fabrication and high degree of disorder in the oxidized (granular) aluminum material used, we observe lifetimes in the microsecond range.
arxiv pdf