1 / 23

Path to Sub-Quantum-Noise-Limited Gravitational-wave Interferometry

Path to Sub-Quantum-Noise-Limited Gravitational-wave Interferometry. MIT Corbitt, Goda, Innerhofer, Mikhailov, Ottaway, Wipf. TeV Particle Astrophysics August 2006. Caltech Australian National University Universitat Hannover/AEI LIGO Scientific Collaboration. Outline.

jena
Download Presentation

Path to Sub-Quantum-Noise-Limited Gravitational-wave Interferometry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Path to Sub-Quantum-Noise-Limited Gravitational-wave Interferometry MITCorbitt, Goda, Innerhofer, Mikhailov, Ottaway, Wipf TeV Particle AstrophysicsAugust 2006 Caltech Australian National University Universitat Hannover/AEI LIGO Scientific Collaboration

  2. Outline • The quantum noise limit in GW ifos • Sub-quantum noise limited ifos • Injecting squeezed vacuum • Setting requirements – the wishlist • Generating squeezed states • Nonlinear optical media – “crystal” • Radiation pressure coupling – “ponderomotive” • Recent progress and present status

  3. Optical Noise • Shot Noise • Uncertainty in number of photons detected a • Higher circulating power Pbsa low optical losses • Frequency dependence a light (GW signal) storage time in the interferometer • Radiation Pressure Noise • Photons impart momentum to cavity mirrorsFluctuations in number of photons a • Lower power, Pbs • Frequency dependence a response of mass to forces  Optimal input power depends on frequency

  4. Initial LIGO Input laser power ~ 6 W Circulating power ~ 20 kW Mirror mass 10 kg

  5. Quantum LIGO I Ad LIGO Test mass thermal Suspension thermal Seismic A Quantum Limited Interferometer Input laser power > 100 W Circulating power > 0.5 MW Mirror mass 40 kg

  6. Some quantum states of light • Heisenberg Uncertainty Principle for EM field • Phasor diagram analogy • Stick  dc term • Ball  fluctuations • Common states • Coherent state • Vacuum state • Amplitude squeezed state • Phase squeezed state Associated with amplitude and phase McKenzie

  7. Consider GW signal in the phase quadrature Not true for all interferometer configurations Detuned signal recycled interferometer  GW signal in both quadratures Orient squeezed state to reduce noise in phase quadrature X- X- X- X+ X- X+ X+ X+ Squeezed input vacuum state in Michelson Interferometer Laser

  8. X- X+ Sub-quantum-limited interferometer Narrowband Broadband BroadbandSqueezed Quantum correlations Input squeezing

  9. Squeezed vacuum states for GW detectors • Requirements • Squeezing at low frequencies (within GW band) • Frequency-dependent squeeze angle • Increased levels of squeezing • Long-term stable operation • Generation methods • Non-linear optical media (c(2) and c(3) non-linearites)  crystal-based squeezing • Radiation pressure effects in interferometers  ponderomotive squeezing

  10. How to make a squeezed state? • Correlate the ‘amplitude’ and ‘phase’ quadratures • Correlations  noise reduction • How to correlate quadratures? • Make noise in each quadrature not independent of the other • (Nonlinear) coupling process needed • For example, an intensity-dependent refractive index couples amplitude and phase • Squeezed states of light and vacuum

  11. Squeezing using nonlinear optical media

  12. Optical Parametric Oscillator SHG

  13. Squeezed Vacuum

  14. Low frequency squeezing at ANU McKenzie et al., PRL 93, 161105 (2004) ANU group  quant-ph/0405137

  15. Injection in a power recycled Michelson interferometer K.McKenzie et al. Phys. Rev. Lett., 88 231102 (2002)

  16. Vahlbruch et al. Phys. Rev. Lett., 95 211102 (2005) Injection in a signal recycled interferometer

  17. Squeezing using radiation pressure coupling

  18. The principle • Use radiation pressure as the squeezing mechanism • Consider an optical cavity with high stored power and a phase sensitive readout • Intensity fluctuations (radiation pressure) drive the motion of the cavity mirrors • Mirror motion is then imprinted onto the phase of the light • Analogy with nonlinear optical media • Intensity-dependent refractive index changes couple amplitude and phase

  19. Key ingredients Low mass, low noise mechanical oscillator mirror – 1 gm with 1 Hz resonant frequency High circulating power – 10 kW High finesse cavities15000 Differential measurement – common-mode rejection to cancel classical noise Optical spring – noise suppression and frequency independent squeezing The “ponderomotive” interferometer

  20. Noise budget

  21. Noise suppression 5 kHz K = 2 x 106 N/mCavity optical mode  diamond rod Displacement / Force Frequency (Hz)

  22. Conclusions • Advanced LIGO is expected to reach the quantum noise limit in most of the band • QND techniques needed to do better • Squeezed states of the EM field appears to be the most promising approach • Crystal squeezing mature • 3 to 4 dB available in f>100 Hz band • Ponderomotive squeezing getting closer • Factors of 2 to 5 improvements foreseeable in the next decade • Not fundamental but technical • Need to push on this to be ready for future instruments

  23. The End

More Related