K.-T. Lin

Deterministic loading and phase shaping of microwaves onto a single artificial atom

  1. W.-J. Lin,
  2. Y. Lu,
  3. P. Y. Wen,
  4. Y.-T. Cheng,
  5. C.-P. Lee,
  6. K.-T. Lin,
  7. K.-H. Chiang,
  8. M. C. Hsieh,
  9. J. C. Chen,
  10. C.-S. Chuu,
  11. F. Nori,
  12. A. F. Kockum,
  13. G.-D. Lin,
  14. P. Delsing,
  15. and I.-C. Hoi
Loading quantum information deterministically onto a quantum node is an important step towards a quantum network. Here, we demonstrate that coherent-state microwave photons, with anoptimal temporal waveform, can be efficiently loaded onto a single superconducting artificial atom in a semi-infinite one-dimensional (1D) transmission-line waveguide. Using a weak coherent state (average photon number N<<1 with an exponentially rising waveform, whose time constant matches the decoherence time of the artificial atom, we demonstrate a loading efficiency of above 94% from 1D semi-free space to the artificial atom. We also show that Fock-state microwave photons can be deterministically loaded with an efficiency of 98.5%. We further manipulate the phase of the coherent state exciting the atom, enabling coherent control of the loading process. Our results open up promising applications in realizing quantum networks based on waveguide quantum electrodynamics (QED).[/expand]
arxiv pdf

Large collective Lamb shift of two distant superconducting artificial atoms

  1. P. Y. Wen,
  2. K.-T. Lin,
  3. A. F. Kockum,
  4. B. Suri,
  5. H. Ian,
  6. J. C. Chen,
  7. S. Y. Mao,
  8. C. C. Chiu,
  9. P. Delsing,
  10. F. Nori,
  11. G.-D. Lin,
  12. and I.-C. Hoi
Virtual photons can mediate interaction between atoms, resulting in an energy shift known as a collective Lamb shift. Observing the collective Lamb shift is challenging, since it can
be obscured by radiative decay and direct atom-atom interactions. Here, we place two superconducting qubits in a transmission line terminated by a mirror, which suppresses decay. We measure a collective Lamb shift reaching 0.8% of the qubit transition frequency and exceeding the transition linewidth. We also show that the qubits can interact via the transmission line even if one of them does not decay into it.
arxiv pdf