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SUMMARY:Quantum Optics Experiments with Multiple Qubits and Multiple Photo
 ns in Superconducting Electronic Circuits - Johannes Fink (ETH\, Zurich)
DTSTART:20091204T143000Z
DTEND:20091204T153000Z
UID:TALK21313@talks.cam.ac.uk
CONTACT:Joe Bhaseen
DESCRIPTION:Superconducting qubits in on-chip microwave resonators allow f
 or the exploration of novel quantum optics regimes enabled by their large 
 and constant dipole coupling strength to individual photons [1]. Utilizing
  these properties we are able to directly prove field quantization in a st
 rongly coupled matter-light system. We observe the square root of n nonlin
 earity of the Jaynes-Cummings energy ladder by measuring the vacuum Rabi s
 pectrum in the presence of coherent [2] and thermal [3] photons n. More re
 cently we have performed measurements with up to three qubits to study cav
 ity mediated multi-qubit interactions. Tuning N qubits in resonance with t
 he cavity field individually\, we demonstrate the square root of N scaling
  of the collective dipole coupling strength as described by the Tavis-Cumm
 ings model [4]. To our knowledge this is the first observation of this non
 linearity in a system\nin which the atom number can be changed one by one 
 in a discrete fashion. In addition\, the energies of both bright and dark 
 coupled multi-qubit/photon\nstates are well explained by the Tavis-Cumming
 s model over a wide range of detunings. Finally\, we present single qubit 
 time-resolved and spectroscopic vacuum Rabi measurements with thermal phot
 on numbers varied by five orders of magnitude. We find good agreement with
  a master equation model over a large range of equivalent thermal field te
 mperatures and observe the emergence of the classical limit of cavity QED 
 as expected from the\ncorrespondence principle. \n\n[1] A. Wallraff et al.
  Nature 431 (2004).\n\n[2] J. M. Fink et al. Nature 454\, 315 (2008).\n\n[
 3] J. M. Fink et al. arXiv:0911.3797 (2009).\n\n[4] J. M. Fink et al. Phys
 . Rev. Lett. 103 (2009).\n\n\n\n
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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