Giulio Cappelli

Entanglement assisted probe of the non-Markovian to Markovian transition in open quantum system dynamics

  1. Chandrashekhar Gaikwad,
  2. Daria Kowsari,
  3. Carson Brame,
  4. Xingrui Song,
  5. Haimeng Zhang,
  6. Martina Esposito,
  7. Arpit Ranadive,
  8. Giulio Cappelli,
  9. Nicolas Roch,
  10. Eli M. Levenson-Falk,
  11. and Kater W. Murch
We utilize a superconducting qubit processor to experimentally probe the transition from non-Markovian to Markovian dynamics of an entangled qubit pair. We prepare an entangled state
between two qubits and monitor the evolution of entanglement over time as one of the qubits interacts with a small quantum environment consisting of an auxiliary transmon qubit coupled to its readout cavity. We observe the collapse and revival of the entanglement as a signature of quantum memory effects in the environment. We then engineer the non-Markovianity of the environment by populating its readout cavity with thermal photons to show a transition from non-Markovian to Markovian dynamics, reaching a regime where the quantum Zeno effect creates a decoherence-free subspace that effectively stabilizes the entanglement between the qubits.
arxiv pdf

Evidence of Josephson coupling in a few-layer black phosphorus planar Josephson junction

  1. Francesca Telesio,
  2. Matteo Carrega,
  3. Giulio Cappelli,
  4. Andrea Iorio,
  5. Alessandro Crippa,
  6. Elia Strambini,
  7. Francesco Giazotto,
  8. Manuel Serrano-Ruiz,
  9. Maurizio Peruzzini,
  10. and Stefan Heun
Setting up strong Josephson coupling in van der Waals materials in close proximity to superconductors offers several opportunities both to inspect fundamental physics and to develop
novel cryogenic quantum technologies. Here we show evidence of Josephson coupling in a planar few-layer black Phosphorus junction. The planar geometry allows us to probe the junction behavior by means of external gates, at different carrier concentrations. Clear signatures of Josephson coupling are demonstrated by measuring supercurrent flow through the junction at milli Kelvin temperatures. Manifestation of Fraunhofer pattern with a transverse magnetic field is also reported, confirming the Josephson coupling. These findings represent the first evidence of proximity Josephson coupling in a planar junction based on a van der Waals material beyond graphene and open the way to new studies, exploiting the peculiar properties of exfoliated black phosphorus thin flakes.
arxiv pdf