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Who are we?

Who are we?. Quantum Information Group Department of Physics Technical University of Denmark (DTU). Quantum Information Processing Group Max Planck Institute for the Science of Light Erlangen, Germany. Collaborators: Lodahl et al (DTU Fotonik) Sørensen et al (NBI)

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Who are we?

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  1. Who are we? Quantum Information Group Department of Physics Technical University of Denmark (DTU) Quantum Information Processing Group Max Planck Institute for the Science of Light Erlangen, Germany Collaborators: Lodahl et al (DTU Fotonik) Sørensen et al (NBI) Filip et al (Palacky Uni) Takeoka, Sasaki et al (NICT) Furusawa et al (Tokyo Uni) Drummond, Corney (UQ) We develop technology for Quantum Computing Quantum Communication Quantum Metrology

  2. Processing and metrology U.L.A., G. Leuchs and C. Silberhorn, Laser and Photonics Reviews, 4, 337 (2010)

  3. What is quantum information? Coding information into a discrete variable: Lecture by Kumar 2D Examples Poster by Jain Lecture by Boyd PhD talks (Tipsmark, Benichi) Lectures by Childress and Imamoglu Coding information into a continuous variable: Coherent state: = Gaussian Examples Squeezed state: = Sqz. Gaussian Single photon: = 1st order HG Lectures by Kippenberg, Hammerer, Polzik and Mølmer

  4. Quantum information protocol • Quantum averaging (PRA, 82, 021801 (2010) ) • Quantum erasure correcting code (Nat. Phot. 2010) • Quantum Key Distribution • Quantum Random number generation (Nat. Phot 2010) • Violating Bells inequality with a hybrid detection system • Hybrid quantum repeater using cat states (arXiv: 1004.0083) • Noiseless Quantum Amplification (Nat. Phys. 2010) • Quantum state generation • Squeezed state / Entangled state • Cat state • Single photon state What do we do? • Quantum metrology/estimation • Phase measurement • Super-resolution with coherent states • Binary coherent state discrimination • (PRL 104, 100505 (2010)) No code With code

  5. Goal To reduce the phase noise of a coherent state through amplification

  6. Deterministic amplification Input-output relation: Gain = G Louisell, W.H I. Phys. Rev. 124 1646 (1961); Haus, H.A. andMullen, J.A. Phys. Rev. 128 5 (1962); Caves, C.M. Phys. Rev. D 26 , 8 (1982).

  7. Probabilistic amplification Gain = G Ralph, T.C. and Lund, A.B. QCMC Proc. of 9th Int. Conf. 155-160 Babichev et al. EPL (2003); Xiang et al. Nat. Ph. 4, 316 (2010); Ferreyrol et al. PRL 104, 123603 (2010); (Zavatta et al. arXiv:1004.3399v1 [quant-ph]; Marek and Filip, PRA 81, 022302 (2010); Fiurasek PRA 80, 053822 2009)

  8. Probabilistic amplification N Marek and Filip, PRA 81, 022302 (2010) a+M aM a+ a Zavatta et al. arXiv:1004.3399; Fiurasek PRA 80, 053822 (2009)

  9. Phase-ConcentrationScheme • Our approach

  10. Phase-ConcentrationScheme • How does it really work?

  11. Experimental Setup - homodyne tomography - diodelaser (809nm) - modecleaning - LO split-off • electro-optical • modulatorsand a • half-waveplate - tap-off measurement - feed-forward

  12. Wigner functions |acoh |2 = 0.186 Usuga, Muller, Wittmann, Marek, Filip, Marquardt, Leuchs and Andersen, Nature Physics (2010)

  13. Phase variance Usuga, Muller, Wittmann, Marek, Filip, Marquardt, Leuchs and Andersen, Nature Physics (2010)

  14. Conclusion Simple Setup ReducedVariance

  15. What is quantum information? Single mode field Degrees of freedom Continuous: Discrete: Photon number, Polarization, Orbital Angular Momentum

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