Hybrid rf SQUID qubit based on high kinetic inductance

  1. J.T. Peltonen,
  2. P. C. J. J. Coumou,
  3. Z.H. Peng,
  4. T. M. Klapwijk,
  5. J. S. Tsai,
  6. and O. V. Astafiev
We report development and microwave characterization of rf SQUID (Superconducting QUantum Interference Device) qubits, consisting of an aluminium-based Josephson junction embedded in
a superconducting loop patterned from a thin film of TiN with high kinetic inductance. Here we demonstrate that the systems can offer small physical size, high anharmonicity, and small scatter of device parameters. The hybrid devices can be utilized as tools to shed further light onto the origin of film dissipation and decoherence in phase-slip nanowire qubits, patterned entirely from disordered superconducting films.

Josephson parametric reflection amplifier with integrated directionality

  1. M. P. Westig,
  2. and T. M. Klapwijk
A superconducting parametric amplifier in the GHz frequency range without a magnetic nonreciprocal circuit element is presented, suitable for circuit quantum electrodynamics (cQED)
and for ultra low-noise microwave detectors employed in astrophysics. It consists of an only one wavelength small nondegenerate Josephson parametric reflection amplifier with integrated directionality. The device has two Josephson junction oscillators, connected via a tailored impedance to an on-chip passive circuit which directs the in- to the output port. The amplifier provides a gain of 20~dB over a bandwidth of 440~MHz and the total photon shot noise at the input corresponds to maximally ∼1.3 photons per second per Hertz of bandwidth. We predict a factor of four increase in dynamic range compared to conventional Josephson parametric amplifiers.