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Overview of quantum noise suppression techniques

This overview explores various techniques for suppressing quantum noise in measurement systems. Topics covered include quantum measurement noise, QND techniques, optical spring effect, speed meters, signal-recycled interferometers, transducers, and local readout schemes.

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Overview of quantum noise suppression techniques

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  1. Overview of quantum noise suppression techniques Helge Müller-Ebhardt, Henning Rehbein, Kentaro Somiya, Roman Schnabel, Karsten Danzmann and Yanbei Chen Max-Planck-Institut für Gravitationsphysik (AEI) Institut für Gravitationsphysik, Leibniz Universität Hannover TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAAA

  2. Quantum measurement noise measurement noise = photon shot noise + radiation pressure noise • free mass dynamics • quantum measurement process • no correlation in shot and back-action noise measurement frequency

  3. Quantum measurement noise measurement noise = photon shot noise + radiation pressure noise • free mass dynamics • quantum measurement process • use correlation in shot and back-action noise measurement frequency

  4. QND techniques

  5. QND techniques balanced homodyne detection at frequency-independent quadrature angle variational outputwith frequency-dependent quadrature angle [Kimble et al, 2001]

  6. QND techniques

  7. QND techniques 10 dB squeezed input at frequency-independent quadrature angle 10 dB squeezed inputwith frequency-dependent quadrature angle [Kimble et al, 2001]

  8. QND techniques

  9. Signal-recycled Michelson interferometer signal-recycling mirror at the dark output port → signal becomes amplified due to an increasing interaction time [Meers, 1988] detuned signal-recycling cavity → optical spring produces additional resonance [Buonanno & Chen, 2001 – 2003]

  10. Optical spring effect a cavity which is detuned from the carrier's frequency makes the power inside the cavity dependent on the motion of the mirror

  11. Optical spring effect a cavity which is detuned from the carrier's frequency makes the power inside the cavity dependent on the motion of the mirror damping anti-damping optical power lags behind the cavity motion → complex spring constant → system becomes unstable possible solution: stable double optical spring

  12. 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]

  13. Speed meter realization two different optical realizations Michelson interferometer Sagnac interferometer [Purdue, 2002] [Chen, 2003]

  14. Optical inertia effect a speed meter which is detuned from the carrier's frequency makes the fluctuating radiation-pressure force dependent on the acceleration of the mirror dynamical mass is modified

  15. Signal-recycled Sagnac interferometer signal-recycling mirror at the dark output port • - two optical resonances • degenerated resonance case → speed meter • bandwidth important factor

  16. Signal-recycled Sagnac interferometer optimize quantum noise in vicinity of standard classical noise budget • AdvLIGO-scale • parameters fixed • 40 kg mirrors • 4 km arms • 800 kW power • optimization • parameters • sr detuning • sr bandwidth • arm cavity bandwidth (250 Hz) • → finesse (150) improves AdvLIGO by 45 % in the event rate

  17. Signal-recycled Sagnac interferometer optimize quantum noise in vicinity of future classical noise budget • AdvLIGO-scale • parameters fixed • 40 kg mirrors • 4 km arms • 800 kW power • optimization • parameters • sr detuning • sr bandwidth • arm cavity bandwidth (125 Hz) • → finesse (300) improves Michelson by 230 % in the event rate

  18. Transducer idea radiation pressure force can transduce motion between front and end mirror of a detuned cavity SQL of a local meter optical bar detector [Braginsky, Gorodetsky & Khalili, 1997]

  19. Position meter transducer infinite optical inertia rigid optical spring zero optical inertia every position meter transducer becomes an optical bar at low frequencies SQL beating narrowband SQL beating

  20. Speed meter transducer infinite optical inertia zero optical inertia speed meter transducer is more flexible at low frequencies

  21. Local readout scheme second carrier senses motion of input mirrors both outputs are optimally filtered

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