Matti Silveri

Theory of remote entanglement via quantum-limited phase-preserving amplification

  1. Matti Silveri,
  2. Evan Zalys-Geller,
  3. Michael Hatridge,
  4. Zaki Leghtas,
  5. Michel H. Devoret,
  6. and S. M. Girvin
We show that a quantum-limited phase-preserving amplifier can act as a which-path information eraser when followed by detection of both quadratures. This beam splitter with gain implements
a continuous joint measurement on the signal sources. As an application, we propose heralded remote entanglement generation between two qubits coupled dispersively to separate cavities. Dissimilar qubit-cavity pairs can be made indistinguishable by simple engineering of the cavity driving fields providing experimental flexibility and the prospect for scalability. Additionally, we find an analytic solution for the stochastic master equation, a quantum filter, yielding a thorough physical understanding of the nonlinear measurement process leading to an entangled state of the qubits.
arxiv pdf

Charge qubit driven via the Josephson nonlinearity

  1. Jani Tuorila,
  2. Matti Silveri,
  3. Mika Sillanpää,
  4. Erkki Thuneberg,
  5. Yuriy Makhlin,
  6. and Pertti Hakonen
We study the novel nonlinear phenomena that emerge in a charge qubit due to the interplay between a strong microwave flux drive and a periodic Josephson potential. We first analyze
the system in terms of the linear Landau-Zener-St\“uckelberg model, and show its inadequacy in a periodic system with several Landau-Zener crossings within a drive period. Experimentally, we probe the quasienergy levels of the driven qubit with an LC-cavity, which requires the use of linear response theory. We also show that our numerical calculations are in good agreement with the experimental data.
arxiv pdf