Domenico Montemurro

Implementation and readout of maximally entangled two-qubit gates quantum circuits in a superconducting quantum processor

  1. Viviana Stasino,
  2. Pasquale Mastrovito,
  3. Carlo Cosenza,
  4. Anna Levochkina,
  5. Martina Esposito,
  6. Domenico Montemurro,
  7. Giovanni P. Pepe,
  8. Alessandro Bruno,
  9. Francesco Tafuri,
  10. Davide Massarotti,
  11. and Halima G. Ahmad
Besides noticeable challenges in implementing low-error single- and two-qubit quantum gates in superconducting quantum processors, the readout technique and analysis are a key factor
in determining the efficiency and performance of quantum processors. Being able to efficiently implement quantum algorithms involving entangling gates and asses their output is mandatory for quantum utility. In a transmon-based 5-qubit superconducting quantum processor, we compared the performance of quantum circuits involving an increasing level of complexity, from single-qubit circuits to maximally entangled Bell circuits. This comparison highlighted the importance of the readout analysis and helped us optimize the protocol for more advanced quantum algorithms. Here we report the results obtained from the analysis of the outputs of quantum circuits using two readout paradigms, referred to as „multiplied readout probabilities“ and „conditional readout probabilities“. The first method is suitable for single-qubit circuits, while the second is essential for accurately interpreting the outputs of circuits involving two-qubit gates.
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