Interferometric speed meter as a low-frequency gravitational-wave detector

1. Interferometric speed meter as a low-frequency gravitational-wave detector Helge Müller-Ebhardt Max-Planck-Institut für Gravitationsphysik (AEI) and Leibniz Universität Hannover TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAAA

2. Speed meter idea measure position difference after time delay → measure speed [Braginsky & Khalili, 1990] conserved momentum usually proportional to speed → real QND (?) no: because the coupling to speed changes conserved momentum [Khalili, 2002]

3. Position meter vs. speed meter RP noise constant below half-linewidth [Purdue & Chen, 2002] broadband RP noise cancellation w/ balanced homodyne detection w/o filters shot noise limited below linewidth can use light masses and squeezing increase only due to signal transfer

4. Interferometric speed meter realizations either Michelson interferometer with additional sloshing cavity or with polarizing optics or Sagnac ifo with non-zero area zero area → insensitive to rotations no arm cavities ring cavities in arms → optimize sensitivity to frequencies of interest size of vacuum system?

5. Demonstration of squeezed zero-area Sagnac Limited mainly by losses in the ifo (5.5%) due to non-optimized coatings for angles of incidence 12.7 dB squeezing inserted 8.2 dB shot noise supression [Eberle et al., 2010]

6. Squeezed LF interferometric GW detector zero-area Sagnac ifo with 10 km long arm cavities, 40 kg test-mass mirrors, linewidth of 80 Hz and a laser power of 90 W at the central beam splitter → 10 kW circulating power low mass low laser power but rather high linewidth allows use of cyrogenics start with pure squeezed state of 12.4 dB optical losses for input-squeezing and detection similar to experiment [Eberle et al., 2010]

7. Squeezed LF interferometric GW detector zero-area Sagnac ifo with 10 km long arm cavities, 40 kg test-mass mirrors, linewidth of 80 Hz and a laser power of 90 W at the central beam splitter → 10 kW circulating power low laser power but rather high linewidth loss in arm cavity: 40 ppm per reflective surface allows use of cyrogenics start with pure squeezed state of 12.4 dB optical losses for input-squeezing and detection similar to experiment [Eberle et al., 2010]

8. Optimization LF GW detector with cyrogenic optics GW detector with 10 km long arm cavities, 10 kW circulating power Saganc ifo w/ 40 kg test-mass, 10 dB squeezing, w/o detuned SR and filter cavities Michelson ifo w/ 200 kg test-mass and detuned SR, w/o squeezing BH-BH inspiral range: Michelson ifo: 5800 Mpc Sagnac ifo: 2600 Mpc 60 cm long suspension and 16 K at test-mass

9. Optimization LF GW detector with cyrogenic optics GW detector with 10 km long arm cavities, 10 kW circulating power Saganc ifo w/ 40 kg test-mass, 10 dB squeezing, w/o detuned SR, filter cavities Michelson ifo w/ 200 kg test-mass, detuned SR w/o squeezing simple integration: Michelson ifo: 1.2 x 10^48 Sagnac ifo: 1.5 x 10^48 60 cm long suspension and 16 K at test-mass

10. Optimization LF GW detector with cyrogenic optics GW detector with 10 km long arm cavities, 50 kW circulating power Saganc ifo w/ 40 kg test-mass, 10 dB squeezing, w/o detuned SR, filter cavities Michelson ifo w/ 200 kg test-mass, detuned SR w/o squeezing simple integration: Michelson ifo: 2 x 10^48 Sagnac ifo: 3 x 10^48 60 cm long suspension and 16 K at test-mass

11. Conclusion • speed meter advantages as LF detector - moderate test-mass weight - compatible with input-squeezing w/o filter cavities - broadband noise spectrum • for LF detector important desicion between position and speed meter • how much circulating power can be tolerated by cooling system • what about thermoelastic noise • what about gravity gradiant and seimic noise • what about optical loss • full parameter optimization: - for what kind of GW sources or for what kind of noise-curve shape - which paramters