1. La réduction du bruit quantique
Pierre-François Cohadon (avec Sheon Chua et l’équipe du LKB)

2. Quantum Noise and Measurement back-action

3. Quantum Noise in GW Detection
Quantum Noise is a limiting noise source
Shot Noise ∝1/√𝑃
Radiation Pressure Noise ∝ 𝑃
Crossover at SQL Frequency
Due to opposite dependency, changing power moves the QN curve along the SQL curve
Options to increase sensitivity
Reduce the amount of noise:
Frequency Independent Squeezing: O3
Frequency Dependent Squeezing: O4
Noise-independent measurement: Variational Readout
Independent measurement and feedforward: EPR Entanglement

4. Variational Readout (circa 2002)
GW signal
RP noise  mechanical response /M2)
Shot
noise
Amplitude noise

5. Variational Readout (circa 2002)
GW signal
RP noise  mechanical response /M2)
Shot
noise
Amplitude noise
Monitoring a different quadrature
allows to cancel RP noise,
but the quadrature depends on c:
frequency-dependent detection required!

6. Variational Readout (circa 2002)
Pros:
Large gain in low-f sensitivity, larger than applied optimal squeezing
Compatible with standard (non-FDS) squeezing injection also
Cons:
Not demonstrated for GWD
Two long cavities needed, regardless of GWD configuration (Broadband, Tuned etc)
Substantial change to GWD readout
No further development planned as of now – future?

7. EPR-Entanglement for FDS (circa 2015)
Pros: Additional long cavities not needed
Cons:
No experimental demonstration (yet)
3 dB less gain w.r.t. current techniques
New ITF readout scheme needed (Local Oscillators)
Considered only an AdV+ potential technology
Included in the “AdV+ Roadmap” document
Brown et al
Ma et al

8. Frequency-Independent Squeezing (circa 1980)
Pros:
Well tested method for GWD (LIGO, GEO600)
Equivalent of changing power
Largely standalone system
Cons:
Potential sensitivity loss due to impact of Anti-Squeezing
LIGO 2013

9. O3 AdV: FIS
December 2016, AEI offered Virgo an in-air frequency-independent squeezer, under preparation since early 2015
Goal: Up to 4dB increase in sensitivity at higher frequencies without decreasing low-frequency sensitivity too much
A. Bertolini (Nikhef)
H. Vahlbruch, M. Mehmet (AEI)

10. O3 AdV: FIS Hosting of the AEI Squeezer in DET Cleanroom Area
Squeezer installed: mode-matching, commissioning in progress
New vacuum flanges
R.Gouaty (LAPP)
Steel rigid frame on simple elastomer pads. A. Bertolini (Nikhef)
Acoustic enclosure F. Carbognani (EGO)

11. FDS: Using FIS with a Filter Cavity
Use the phase response of a “Filter Cavity” to rotate the squeezing ellipse as a function of frequency
One Filter Cavity is sufficient for ellipse rotation for GWD in the broadband tuned-signal recycling case.
Detuned SR needs two cavities
FIS + Filter Cavity

12. FDS: Using FIS with a Filter Cavity
Pros:
Tested and demonstrated method (next slide)
Compatible with current GWD readout
Largely standalone system to the ITF
Cons:
Needs the additional Filter Cavity, with linewidth matching SQL crossover of ~ 50 Hz

13. FDS with Filter Cavities around the World
First demonstrated in 2005 in MHz (AEI)
Theoretical studies into designs, optical loss requirements (2003 to present)
Audio-band demonstration 2016 (MIT, ANU)
Setups coming online in 2018
TAMA (NAOJ, APC, Nikhef)
CALVA at LAL Orsay (with LKB,LMA and LAPP)
S. Chelkowski et al
E. Oelker et al
E. Capocasa et al

14. O4 AdV: FDS with Filter Cavity
Preliminary Conceptual Design work started
To lead to WBS and FDS TDR
Authors for the Conceptual Design sections listed below
A. Bertolini (Nikhef)
Now included in the “Future of AdV” or “AdV+ Roadmap” document
Sensitivity Curves: A. Bertolini, S. Chua, R. Flaminio, J. P. Zendri
Filter cavity (optics): M. Tacca, M. Barsuglia, M. De Laurentis, P. Gruning, J. Degallaix, R. Flaminio, R. Bonnand
Filter Cavity (vacuum system): B. Mours, A .Bertolini
Squeezing source: S.Chua, H.Vahlbruch, E. Genin, R.Bonnand
Backscattering: L. Conti, A. Bertolini, S. Chua

15. O4 AdV: FDS with Filter Cavity
Preliminary Infrastructure Conceptual Design (LAPP, Nikhef)
New meetings past

16. O4 AdV: FDS with Filter Cavity
Squeezed Light Source (LKB, AEI, EGO) : In-air or In-vacuum
As of today: Decision to wait on the various GWD squeezing experiments coming online in the next 6 months
Squeezing Mini-tower is needed for both configurations

17. O4 AdV: FDS with Filter Cavity
The “AdV+ Roadmap” document builds on the Preliminary FDS Conceptual Design work. However, perhaps the final Conceptual Design will have impact from the Roadmap Document
Considerations for “AdV+ Roadmap” Document Chapter on FDS to finalise:
Decision on Filter Cavity length
Decision on residual pressure in the Filter Cavity tanks
Changes needed to SDB1 in O4
Timeline
Costs

18. Summary Squeezing is (now) considered an important upgrade of AdV
First step: FIS for O3 with AEI squeezer
Squeezer delivered early 2018
Installation/Commissioning in progress
Next step : FDS
Planned for 04
A number of pending decisions, including in-air or in-vacuum squeezer
ExSqueez project between LAL, LMA, LAPP and LKB to gain expertise