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GEO600: The First Application of Squeezed Light

GEO600: The First Application of Squeezed Light. Roman Schnabel, for the GEO600 group, the Quantum Interferometry Group, and the LSC Albert-Einstein-Institut (AEI) Institut für Gravitationsphysik Leibniz Universität Hannover. Outline. Introduction to Squeezed Light

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GEO600: The First Application of Squeezed Light

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  1. GEO600: The First Application of Squeezed Light Roman Schnabel, for the GEO600 group, the Quantum Interferometry Group, and the LSC Albert-Einstein-Institut (AEI) Institut für Gravitationsphysik Leibniz Universität Hannover

  2. Outline • Introduction to Squeezed Light • The first squeezed-light laser for GW detectors • Sensitivity improvement of GEO600 with squeezed light • Squeezed light as a key-technology for GW astronomy

  3. Gravitational Waves h: Gravitational wave astronomy requires observatories that can detect h < 10-23 (over a band from e.g. 100Hz - 200Hz) • Merging neutron stars. Numerical relativity simulation of gravitational waves emitted from two neutron stars which are about to merge in 4 ms [Rezzolla, AEI]. 3

  4. Mirror 1 Mirror 2 Laser 50% Beam splitter Photo diode Gravitational Wave Detection 1) Test masses > km 2) Laser light 3) Interference Photo-electric current modulated at GW frequency 4) Photo-electric effect 4

  5. N Photo-Electric Current (No signal, but photon shot noise) Photons per time interval Time intervals 5

  6. N Photo-Electric Current (GW signal?) Photons per time interval Time intervals 6

  7. Photon Counting Statistics Coherent state Relative shot-noise Probability [rel. units] Photon number N 7

  8. Heating by light absorption Photo diode Increasing the Light Power Mirror 1 Power-recycling mirror High power laser Mirror 2 Photo-electric current 8

  9. Is there a possibility to increase the signal/quantum noise–ratio without increasing the laser power? Yes, by squeezed laser light! 9

  10. Shot-Noise in an Interferometer Mirror Beam splitter Laser Due to zero point fluctuations (vacuum noise) Photo diode [Caves, Phys. Rev. D 23, 1693 (1981)] 10

  11. Squeezing the Shot-Noise Mirror C. M. Caves (1981): Reduction of quantum noise with squeezed light Beam splitter Laser Squeezed light laser Faraday Rotator Photo diode [Caves, Phys. Rev. D 23, 1693 (1981)] 11

  12. “Squeezed” Counting Statistics Squeezing factor: 10 dB Noise squeezing Probability [rel. units] Squeezing factor: 3 dB Photon number N 12

  13. N Photo-Electric Current (No signal) Photons per time interval Time intervals 13

  14. N Photo-Electric Current - Squeezed Squeezing the noise of a random process without a measurement!? Quantum mechanics: Squeezing requires time/energy (and amplitude/phase quadrature) entangled photons Photons per time interval Time intervals 14

  15. Squeezing in the Wave Picture X1 Quadrature squeezing at sideband frequency W1 + + Wc-W1 + Wc+W1 Wc X2 W + 15

  16. The GEO600 Squeezed Light Laser 16

  17. Generation of Squeezed Light (PDC) c2-nonlinear crystal: MgO:LiNbO3 Pump field input (cw, 532nm) Squeezed field output (cw, 1064nm) by parametric down-conversion (PDC) Standing wave cavity 17

  18. History of Squeezed Light Generation First squeezed light: [Slusher et al., PRL 55, 2409 (1985)] Research labs with squeezed light (not complete): • Kimble (CalTech): teleportation: [Furuzawa et al., SCIENCE 282, 706 (1998)] • Grangier (Orsay); kitten: [Ourjoumtsev et al., SCIENCE, 312, 83 (2006)] • Schiller and Mlynek (Konstanz): tomography: [Nature 387, 471 (1997).] • Bachor and Lam (Canberra): 6dB at 1064nm [J. Opt. B 1, 469 (1999).] • Leuchs (Erlangen); ~7 dB pulsed [Opt. Lett. 33, 116 (2008).] • Polzik (Copenhagen), [Neergaard-Nielsen et al., PRL 97, 083604 (2006)] • Furusawa (Tokyo); 9 dB: [Takeno et al., Opt. Express 15, 4321 (2007).] • Fabre (Paris), Zhang, Peng (Shanxi); • Andersen (Copenhagen); Mavalvala (MIT),... 18

  19. History of Squeezed Light Generation Research & development towards the first application of squeezed light • McClelland (ANU), power-recycling [McKenzie et al., PRL 88, 231102 (2002)] • McClelland (ANU), audio-band [McKenzie et al., PRL 93, 161105 (2004)] • RS (LUH), signal-recycling [Vahlbruch et al., PRL 95, 211102 (2005)] • RS (LUH), control scheme [Vahlbruch et al., PRL 97, 011101 (2006)] • RS (LUH), full band-width [Vahlbruch et al., New Journal of Phys. 9, 371 (2007)] • Mavalvala (MIT), suspended mirrors [Goda et al., Nature Phys. 4, 472 (2008)] • RS (LUH), 10dB [Vahlbruch et al., PRL 100, 033602 (2008)] • RS (LUH), turn-key source [Vahlbruch et al., CQG 27, 084027 (2010)] • Recent review: • [R.S. et al., Nature Comm. 1:121 doi: 10.1038/ncomms1122 (2010)] 19

  20. Transport to the GEO600 GW Detector 20

  21. GEO600: Squeezed Light in Application Observatory noise without squeezed light With squeezed light

  22. Squeezing the Shot-Noise (SN) and the Radiation Pressure Noise (PRN) [Jaekel and Reynaud, Europhys. Lett. 13, 301 (1990)] Laser Filter cavities Faraday Rotator Squeezed light laser [Kimble et al., Phys. Rev. D 65, 022002 (2001)] 22

  23. QND-Regime Squeezing SN and RPN [Jaekel, Reynaud 1990] Shot noise Squeezed Light Input (8dB) Radiation pressure noise (SQL)

  24. Summary • GEO600 now uses squeezed light and achieves its best ever sensitivity (at shot-noise limited frequencies) • A real application of entangled photons in squeezed light has been realized • Squeezing is mature and might become a key-technology in all future GW observatories, such as ET

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