A. A. Shtygashev

Decay of transmon qubit strongly coupled with a continuum

  1. Ya. S. Greenberg,
  2. A. A. Shtygashev,
  3. and O. V. Kibis
We investigate the decay of three-level artificial atom, a superconducting transmon qubit which interacts with a continuum of modes in an open one-dimensional waveguide. For strong
interaction of transmon with a continuum we obtain analytical expressions for the frequency shifts and widths of the resonances the values of which are calculated numerically for the Gaussian density of states. We show that the coupling between the second level and ground state of a transmon significantly influences the decay of the third transmon level.
arxiv pdf

Non-Hermitian Hamiltonian approach to the microwave transmission through one- dimensional qubit chain

  1. Ya. S. Greenberg,
  2. and A. A. Shtygashev
We investigate the propagation of microwave photons in a one-dimensional waveguide interacting with a number of artificial atoms (qubits). Within the formalism of projection operators
and non-Hermitian Hamiltonian approach we develop a one-photon approximation scheme for the calculation of the transmission and reflection factors of the microwave signal in a waveguide which contains an arbitrary number \emph{N} of non-interacting qubits. It is shown that for identical qubits in the long-wave limit a coherent superradiance state is formed with the width being equal to the sum of the widths of spontaneous transitions of \emph{N} individual qubits.
arxiv pdf