A. M. Zagoskin

Quantum electrodynamics of non-demolition detection of single microwave photon by superconducting qubit array

  1. P. Navez,
  2. A. G. Balanov,
  3. S. E. Savel'ev,
  4. and A. M. Zagoskin
By consistently applying the formalism of quantum electrodynamics we developed a comprehensive theoretical framework describing the interaction of single microwave photons with an array
of superconducting transmon qubits in a wave guide cavity resonator. In particular, we analyze the effects of microwave photons on the arrays response to a weak probe signal exciting the resonator. The study reveals that a high quality factor cavities provide better spectral resolution of the response, while cavities with moderate quality factor allow better sensitivity for a single photon detection. Remarkably, our analysis showed that a single-photon signal can be detected by even a sole qubit in cavity under the realistic range of system parameters. We also discuss how quantum properties of the photons and electrodynamical properties of resonators affect the response of qubits array. Our results provide an efficient theoretical background for informing the development and design of quantum devices consisting of arrays of qubits.
arxiv pdf

Feedback-controlled adiabatic quantum computation

  1. R. D. Wilson,
  2. A. M. Zagoskin,
  3. S. Savel'ev,
  4. M. J. Everitt,
  5. and Franco Nori
We propose a simple feedback-control scheme for adiabatic quantum computation with superconducting flux qubits. The proposed method makes use of existing on-chip hardware to monitor
the ground-state curvature, which is then used to control the computation speed to maximize the success probability. We show that this scheme can provide a polynomial speed-up in performance and that it is possible to choose a suitable set of feedback-control parameters for an arbitrary problem Hamiltonian.
arxiv pdf