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Noiseless phase amplification using noise - QNLO

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					                             Who are we?




     Quantum Information Group              Quantum Information Processing Group
       Department of Physics            Max Planck Institute for the Science of Light
Technical University of Denmark (DTU)                Erlangen, Germany


                                                     Collaborators:
                                                     Lodahl et al (DTU Fotonik)
                We develop technology for            Sørensen et al (NBI)
                Quantum Computing                    Filip et al (Palacky Uni)
                Quantum Communication                Takeoka, Sasaki et al (NICT)
                Quantum Metrology                    Furusawa et al (Tokyo Uni)
                                                     Drummond, Corney (UQ)
Processing and metrology




          U.L.A., G. Leuchs and C. Silberhorn, Laser and Photonics Reviews, 4, 337 (2010)
             What is quantum information?
 Coding information into a discrete variable:

       N                                  cH H  cV V                    Lecture by Kumar

   cu un             2D Examples
                                          c0 0  c1 1                    Poster by Jain

      n 0                                c LG  c LG                Lecture by Boyd

                                          c   c                 PhD talks (Tipsmark, Benichi)

                                          c   c                   Lectures by Childress
                                                                         and Imamoglu

 Coding information into a continuous variable:
             
                                                Coherent state:       (x) = Gaussian
      ( x) x dx              Examples
                                                Squeezed state:       (x) = Sqz. Gaussian
           
                                                Single photon:        (x) = 1st order HG
      ( x)   x                           Lectures by Kippenberg, Hammerer, Polzik and Mølmer
                                 What do we do?
                                          Quantum information protocol
 Quantum state generation                 • Quantum averaging (PRA, 82, 021801 (2010) )
 • Squeezed state / Entangled state                                     V
                                                                             1
                                                                               V1  V2 
 • Cat state                                                                 2
 • Single photon state                                                  1 1 1 1 
                                                                            
                                                                        V 2  V1 V2 
                                                                                   

                                          • Quantum erasure correcting code (Nat. Phot. 2010)

                                                          No code




                                                         With code

Quantum metrology/estimation
• Phase measurement                       • Quantum Key Distribution
• Super-resolution with coherent states   • Quantum Random number generation (Nat. Phot 2010)
• Binary coherent state discrimination
(PRL 104, 100505 (2010))




                                          • Violating Bells inequality with a hybrid detection system
                                          • Hybrid quantum repeater using cat states (arXiv: 1004.0083)
                                          • Noiseless Quantum Amplification (Nat. Phys. 2010)
                             Goal



To reduce the phase noise of a coherent state through amplification
                     Deterministic amplification




                                                    Gain = G


                                            Input-output relation:
                                         aout  Gain  G 1v



Louisell, W.H I. Phys. Rev. 124 1646 (1961); Haus, H.A. and Mullen, J.A. Phys. Rev. 128 5 (1962); Caves, C.M. Phys. Rev. D 26 , 8 (1982).
                    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)
             Probabilistic amplification




                              N
                              aa++
                                 M
                                          aa M



                                                                 Marek and Filip, PRA 81,
                                0  1                         022302 (2010)


                        a   1  2 2
                          



                      aa   0  2 1  2
                          



Zavatta et al. arXiv:1004.3399; Fiurasek PRA 80, 053822 (2009)
Phase-Concentration Scheme
             Our approach
Phase-Concentration Scheme
       How does it really work?
                  Experimental Setup




- diode laser (809nm)   - electro-optical    - tap-off        - homodyne
- mode cleaning           modulators and a     measurement      tomography
- LO split-off            half-wave plate    - feed-forward
                         Wigner functions

                               |coh |2 = 0.186




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




Usuga, Muller, Wittmann, Marek, Filip, Marquardt, Leuchs and Andersen, Nature Physics (2010)
Conclusion

        Simple Setup




       Reduced Variance
          What is quantum information?
                                                         
         Single mode field                          [ a, a ]  1
            
                 ˆ aeikr it  a  eikr it 
                                                              
  ˆ
  E i           e ˆ             ˆ                 x aa
           2 0V                                             
                                                   p  i (a  a)

  Degrees of freedom

Continuous:   x, p ,  , 
Discrete: Photon number, Polarization, Orbital Angular Momentum

				
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posted:12/12/2012
language:English
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