Luigi Di Palma

Discriminating the Phase of a Coherent Tone with a Flux-Switchable Superconducting Circuit

  1. Luigi Di Palma,
  2. Alessandro Miano,
  3. Pasquale Mastrovito,
  4. Davide Massarotti,
  5. Marco Arzeo,
  6. Giovanni Piero Pepe,
  7. Francesco Tafuri,
  8. and Oleg A. Mukhanov
We propose a new phase detection technique based on a flux-switchable superconducting circuit, the Josephson digital phase detector (JDPD), which is capable of discriminating between
two phase values of a coherent input tone. When properly excited by an external flux, the JDPD is able to switch from a single-minimum to a double-minima potential and, consequently, relax in one of the two stable configurations depending on the phase sign of the input tone. The result of this operation is digitally encoded in the occupation probability of a phase particle in either of the two JDPD wells. In this work, we demonstrate the working principle of the JDPD up to a frequency of 400 MHz with a remarkable agreement with theoretical expectations. As a future scenario, we discuss the implementation of this technique to superconducting qubit readout. We also examine the JDPD compatibility with the single-flux-quantum architecture, employed to fast-drive and measure the device state.
arxiv pdf

A hybrid ferromagnetic transmon qubit: circuit design, feasibility and detection protocols for magnetic fluctuations

  1. Halima Giovanna Ahmad,
  2. Valentina Brosco,
  3. Alessandro Miano,
  4. Luigi Di Palma,
  5. Marco Arzeo,
  6. Domenico Montemurro,
  7. Procolo Lucignano,
  8. Giovanni Piero Pepe,
  9. Francesco Tafuri,
  10. Rosario Fazio,
  11. and Davide Massarotti
We propose to exploit currently available tunnel ferromagnetic Josephson junctions to realize a hybrid superconducting qubit. We show that the characteristic hysteretic behavior of
the ferromagnetic barrier provides an alternative and intrinsically digital tuning of the qubit frequency by means of magnetic field pulses. To illustrate functionalities and limitation of the device, we discuss the coupling to a read-out resonator and the effect of magnetic fluctuations. The possibility to use the qubit as a noise detector and its relevance to investigate the subtle interplay of magnetism and superconductivity is envisaged.
arxiv pdf