1. Roman Schnabel for the AEI-Division Karsten Danzmann
Measurement and Observation at the Quantum Limit at the Albert-Einstein Institute Hannover
Roman Schnabel
for the AEI-Division Karsten Danzmann

2. AEI-Division Prof. Karsten Danzmann
Dr. Hartmut Grote
Gravitational wave detector GEO600
Dr. Harald Lück
GEO600+HF and Einstein Telescope
Priv.-Doz. Dr. Benno Willke
Laser Development, and Advanced LIGO
Dr. Stefan Goßler
10 m Prototype facility*
Priv.-Doz. Dr. Gerhard Heinzel
Space Interfero-metry
Prof. Roman Schnabel
Quantum
Interfero-metry
* Led by external member
Prof. Ken Strain, Glasgow

3. The GEO600 Project
Michelson Laser Interferometer (600m) for GW detection
German-British collaboration, location Hannover / Germany
Limited by quantum noise
U Birmingham
U Mallorca
Glasgow

4. GEO 600 GEO-HF: - 30kW - DC readout - OMC - Tuned, broadband SR
H. Grote
GEO 600
GEO-HF:
- 30kW
- DC readout
- OMC
- Tuned, broadband SR
- Squeezed Light
C. Caves (1981):
Replace the vacuum state (zero-point fluctuations) by a squeezed state! 4 4

5. Shot noise
squeezed

6. This is not just a proof of principle!
GEO600 regularly uses squeezed light during its observational runs.
An application of quantum metrology today!
Regular use: [Grote, Danzmann, Dooley, Schnabel, Vahlbruch, Phys. Rev. Lett., accepted (2013)]

7. The Einstein-Telescope
H. Lück
The Einstein-Telescope
10 km arms
under ground
Cryo-cooled silicon mirrors nm
Squeezed light at nm and nm (~10 dB)
[M. Punturo et al.,
Class. Quantum Grav.
(2010)]
European conceptual design study, delivered May 2011 7

8. The Advanced LIGO 180 W-Laser
B. Willke
The Advanced LIGO 180 W-Laser
LIGO Livingston
Design and fabrication at the AEI/LZH.
Three pre-stabilized 180 W- systems installed at LIGO.
[Winkelmann et al., Appl. Phys. B. (2011);
Kwee et al., Opt. Express (2012)] 8

9. Light Power Stabilisation
B. Willke
Light Power Stabilisation
Relative power noise (shot-noise limited): Hz- 1/2
4 Photodiodes, 50mA each, aligned for lowest pointing coupling 9

10. Light Power Stabilisation (>MHz)
B. Willke
Light Power Stabilisation (>MHz)
Relative power noise of 150W: RPN=10-10 Hz-1/2
corresponding to 32 A photo current. 10

11. 134 W of TEM00 green light B. Willke
1064nm
(in)
1064nm
(out)
(130W in TEM00), single frequency, single mode, 90% conversion efficiency,
stable for more than 48 hours.
[T. Meier et al., Opt. Lett. 35, 3742 (2010)] 11

12. 82 W of light in the LG33 Mode B. Willke
Transfer of 140W HG00 into 82W LG33 with 95% mode purity.
Offers reduction of thermal noise in future GW detectors.
On-going collaboration with University of Birmingham. 12

13. The 10m-AEI-Prototype Facility
S. Goßler / K. Strain
The 10m-AEI-Prototype Facility
UHV system, 180° view
100 m3 volume, about 5 x10-8 mbar
(dominated by water vapour, air in 10-9 mbar region) 13

14. The 10m-AEI-Prototype Facility
S. Goßler / K. Strain
The 10m-AEI-Prototype Facility
Suspended Tables,
fres < 300 mHz 14

15. Vertical Isolation Performance
S. Goßler / K. Strain
Vertical Isolation Performance
101
100
10-1
10-2
10-3
10-4
10-5
10-6
10-7
10-8
Vertical ground motion
Noise spectral density [ mm / Hz -1/2 ]
Vertical table motion
Theoretical model
Frequency [Hz] 15

16. Monolithic Mirror Suspensions
S. Goßler / K. Strain
Monolithic Mirror Suspensions
First blade spring stage
Design:
IGR Glasgow
Monolithic Stages:
Mechanics:
AEI Hannover
Upper mass with
second blade spring stage
Penultimate mass
20µm suspension fibers
100g mirror 16

17. Squeezed Light R. Schnabel
Wigner function of >10dB squeezed vacuum state
Parametric down-conversion in c2-nonlinear crystal in standing-wave cavity
[Vahlbruch et al., Phys. Rev. Lett. (2008)]
[Vahlbruch et al., New J. Phys. (2007)]
[Eberle et al., Phys. Rev. Lett. (2010)]
[Mehmet et al., Opt. Express (2011)]
[Ast et al., Opt. Lett. (2012)] 17

18. Squeezed Light R. Schnabel Observed squeezing: Up to 12.7 dB @ 1064 nm
Spectrum down to 1 Hz / up to 1 GHz
The GEO600 Squeezer:
Fully controlled, automated source of up to 10 dB from 10 Hz to > 10 kHz
Parametric down-conversion in c2-nonlinear crystal in standing-wave cavity
[Vahlbruch et al., Phys. Rev. Lett. (2008)]
[Vahlbruch et al., New J. Phys. (2007)]
[Eberle et al., Phys. Rev. Lett. (2010)]
[Mehmet et al., Opt. Express (2011)]
[Ast et al., Opt. Lett. (2012)] 18

19. The GEO600 Squeezed Light Laser
R. Schnabel
The GEO600 Squeezed Light Laser 19

20. Entangled Light for Metrology
R. Schnabel
Entangled Light for Metrology
Einstein- Podolsky- Rosen entangled light beams
[S. Steinlechner et al., arXiv: ] 20

21. Nano-Structured Mirrors
R. Schnabel
Nano-Structured Mirrors
On-going collaboration with Jena University and IGR Glasgow
Goal: reduction of mirror thermal noise
Up to 100% Reflection (surface waveguide mirror)
0th
-1st
+1st
0th
Finesse ~ 3000
Si crystal
Destruktive Interference
[Brückner, RS, Tünnermann et al., Phys. Rev. Lett. 104, (2010)] 21

22. Nano-Structured Mirrors
R. Schnabel
Nano-Structured Mirrors
On-going collaboration with Jena University and IGR Glasgow
Goal: reduction of mirror thermal noise
Joint publications on nano-structured mirrors, suspended in the Glasgow 10m prototype facility
Barr, Strain, Tünnermann, RS et al., Opt. Lett. 36, 2746 (2011).
Friedrich, Strain, Tünnermann, RS et al., Opt. Express 19, (2011).
Edgar, Strain, Tünnermann, RS et al., Class. Quantum Grav. 27, (2010).
Edgar, Strain, Tünnermann, RS et al., Opt. Lett. 34, 3184 (2009).
Hallam, Strain, RS et al., J. Opt. A: Pure Appl. Opt. 11, (2009). 22

23. Absorption Measurements on Silicon
R. Schnabel
Absorption Measurements on Silicon
T = 300 K
[J. Steinlechner et al., submitted to Class. Quantum Grav. (2013)] 23

24. Opto-Mechanics R. Schnabel 40 nm thickness meff = 80 ng
Q-factor =
fres = 130 kHz
R = nm
J. D. Thompson, … & J. G. E. Harris, Nature 452, (2008)
T.J. Kippenberg and K.J. Vahala, Science 321, 1172 (2008) 24

25. Optically cooled membrane resonance:
R. Schnabel
Opto-Mechanics
Optically cooled membrane resonance:
From 300K to 8K 25

26. Proposal for an AEI / IGR IMPP Topic: “Ultra-quite Mirror Test Masses”
Goals:
Design and test of novel low-noise kg-sized mirror systems
Possibly based on silicon
For GW detectors operated at low temperatures
For quantum physical experiments with massive objects
Further strengthening the GWD related expertise in north Europe
GEO600: 5 kg fused silica mirror with monolithic fibre suspension 26

27. Proposal for an AEI / IGR IMPP Topic: “Quantum Non-Demolition Interferometry”
Goals:
Design and test of novel interferometer techniques
to surpass the standard quantum limit of gravitational wave detection
generating entangled motion of kg-sized test masses (conditional states)
A. Franzen, AEI
Michelson interferometer with two readouts proposed for the generation of entangled mirrors 27

28. A B
X1com(t)
X2diff(t)
BHD:
Low finesse
Michelson Interferometer with 2x balanced homodyne detection (BHD):
® Information on which the mechanical state can be conditioned*
*also: [M. Haixing, S. Danilishin, H. Müller-Ebhardt, Y. Chen, New J. Phys. 12, (2010)] 28

29. Conditionally Pure Mirror States
pA(t) − pB(t)
xA(t) − xB(t)
Problem:
Thermal occupation number of mechanical oscillator:
For pendulum with period 1s:
W = 2p Hz
n<1 ! ® T < 4∙10-10 K ! 29

30. Summary The AEI’s expertise: Operation and improvement of GEO600
Design activity on the Einstein Telescope
Ultra-stable high-power laser light
Squeezed and entangled light
A new low-noise 10m prototype facility
Research on nano-structured and silicon mirrors
Opto-mechanics with micro-oscillators
Combining these with the expertise in Scotland (IGR Glasgow) on GW detectors, low noise mirror suspensions, and low temperature experiments will provide an outstanding position for R&D for GW detectors and quantum physical experiments with massive objects.