Pasquale Mastrovito

On-chip microwave coherent source with in-situ control of the photon number distribution

  1. Pasquale Mastrovito,
  2. Halima Giovanna Ahmad,
  3. Martina Esposito,
  4. Davide Massarotti,
  5. and Francesco Tafuri
Coherent photon sources are key elements in different applications, ranging from quantum sensing to quantum computing. In the context of circuit quantum electrodynamics, there have
been multiple proposals for potential coherent sources of photons, but a well established candidate is still missing. The possibility of designing and engineering superconducting circuits behaving like artificial atoms supports the realization of quantum optics protocols, including microwave photons generation. Here we propose and theoretically investigate a new design that allows a tunable photon injection directly on-chip. The scheme is based on initiating a population inversion in a superconducting circuit that will act as the photon source of one or multiple target resonators. The key novelty of the proposed layout consists in replacing the usual capacitive link between the source and the target cavity with a tunable coupler, with the advantage of having on-demand control on the injected steady-state photons. We validate the dynamical control of the generated coherent states under the effect of an external flux threading the tunable coupler and discuss the possibility of employing this scheme also in the context of multiple bosonic reservoirs.
arxiv pdf

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