A. R. Akhmerov

Demonstration of an ac Josephson junction laser

  1. M.C. Cassidy,
  2. A. Bruno,
  3. S. Rubbert,
  4. M. Irfan,
  5. J. Kammhuber,
  6. R. N. Schouten,
  7. A. R. Akhmerov,
  8. and L.P.Kouwenhoven
Superconducting electronic devices have re-emerged as contenders for both classical and quantum computing due to their fast operation speeds, low dissipation and long coherence times.
An ultimate demonstration of coherence is lasing. We use one of the fundamental aspects of superconductivity, the ac Josephson effect, to demonstrate a laser made from a Josephson junction strongly coupled to a multi-mode superconducting cavity. A dc voltage bias to the junction provides a source of microwave photons, while the circuit’s nonlinearity allows for efficient down-conversion of higher order Josephson frequencies down to the cavity’s fundamental mode. The simple fabrication and operation allows for easy integration with a range of quantum devices, allowing for efficient on-chip generation of coherent microwave photons at low temperatures.
arxiv pdf

Realization of microwave quantum circuits using hybrid superconducting-semiconducting nanowire Josephson elements

  1. G. de Lange,
  2. B. van Heck,
  3. A. Bruno,
  4. D. J. van Woerkom,
  5. A. Geresdi,
  6. S. R. Plissard,
  7. E. P. A. M. Bakkers,
  8. A. R. Akhmerov,
  9. and L. DiCarlo
We report the realization of quantum microwave circuits using hybrid superconductor-semiconductor Josephson elements comprised of InAs nanowires contacted by NbTiN. Capacitively-shunted
single elements behave as transmon qubits with electrically tunable transition frequencies. Two-element circuits also exhibit transmon-like behavior near zero applied flux, but behave as flux qubits at half the flux quantum, where non-sinusoidal current-phase relations in the elements produce a double-well Josephson potential. These hybrid Josephson elements are promising for applications requiring microwave superconducting circuits operating in magnetic field.
arxiv pdf