1. New directions for terrestrial detectors
The next ten years…
Nergis Mavalvala
(just a middle child)
Rai’s party, October 2007

2. Rai-isms
Zacharias’s picture
“This isn’t half stupid” = brilliant!
“What do you know how to do?” “Well, I’ve taken 8.07, 8.08,…, 8.321…” “Oh come off it, what do you really know?” “Err, I can machine.” “You’re alright”
Squash or swimming?

3. Rai-isms
“I gotta pee, walk with me to the boy’s room.” (At door) “Err…” “Unh, you can’t come with me. I’ll be right out” (1991)
“Rai, I can’t read your annotation here” (Long pause, staring at page) “I can’t read it either” (1996)
Q: ”What’s a reasonable start-up to ask for, Rai?” A: “I think it’ll be hard to go for more than $50,000” (2001)

4. Why do we need new directions?
Because Rai is never really going to retire

5. The ideas out there… Will they work, or are we crazy?
Sub-quantum-limited interferometers
Novel classical readouts
Quantum mechanical antics
Subterranean interferometers
Cryogenic detectors

6. Quantum noise limited Weiss LIGO Shot noise Radiation pressure noise
Advanced LIGO

8. Sub-quantum interferometers

9. Quantum mechanics of light
Heisenberg Uncertainty Principle for EM field
Coherent state (laser light)
Squeezed state
Two complementary observables
Make on noise better for one quantity, BUT it gets worse for the other
X+ and X- associated with amplitude and phase
McKenzie

10. Quantum Noise in an Interferometer
First proposed … C.M. Caves, PR D (1981)
Proof-of-principle demonstration … M. Xiao et al., PRL (1987)
More realistic configurations demonstrated …
Power Recycled Michelson K. McKenzie et al., PRL (2002)
Power and Signal Recycled Michelson H. Vahlbruch et al., PRL (2005)
Suspended prototype Goda et al. (2007)
Laser X+ X- X+ X- X+ X- X+ X-

11. Squeezed input

12. Squeezed Input Interferometer
Laser
GW Detector
Squeeze
Source
Faraday isolator
The squeeze source drawn is a ponderomotive squeezer, but it could be any other squeeze source, e.g. an optical parametric oscillator.
Squeeze
Source
Homodyne Detector
GW Signal

13. Sub-quantum-limited interferometer
Narrowband unsqueezed
Broadband unsqueezed
Broadband Squeezed X+ X-
Quantum correlations
Input squeezing

14. Squeezing injected @ the 40m prototype @ Caltech
Goda et al. (2007)

15. 40m squeezing gang

16. High laser power radiation pressure ↔ mechanical oscillator coupling

17. Radiation-mirror coupling
1. Light with amplitude fluctuations DA
incident on mirror
Movable mirror
Field transformation:
Incident laser light is in a coherent state (noise ball)
Coupling to mirror motion
Reflected light is in a squeezed state (noise ellipse)
Remember LLAMA?
2. Radiation pressure due to DA causes mirror to move by Dx
3. Phase of reflected light Df depends on mirror position and hence light amplitude, i.e DA  Dx  Df

18. A radiation pressure dominated interferometer
Key ingredients
Low mass, low noise mechanical oscillator mirror – 1 gm with 1 Hz resonant frequency
High circulating power – 10 kW
High finesse cavities 10000
Differential measurement – common-mode rejection to cancel classical noise
Optical spring – noise suppression and frequency independent squeezing

19. Observable quantum effects
Squeezed states of light
Entanglement due to mirror motion
Quantum radiation pressure noise
Squeezed states of the mirror
Like atoms
Figure of merit for quantumness Thermal occupation number
Optical cooling and trapping of the mini-mirror

20. Classical radiation pressure effects
Stiffer than diamond
6.9 mK
Stable OS
Radiation pressure dynamics
Optical cooling

21. Quantum radiation pressure effects
Entanglement
Squeezing
Mirror-light entanglement
Squeezed vacuum generation

22. Radiation pressure gang
Dave Ottaway
Nick Smith
Rai’s door art
Tim Bodiya

23. Novel readouts
Evading the back action noise
radiation pressure

24. Novel readouts Speedmeters
Measure momentum, not position
“Optical bar” and “optical lever” configurations
Use radiation pressure to transfer the motion of end masses to vertex for local readout
Intra-cavity readouts
Potential to operate at high sensitivity with much lower power than conventional interferometers

25. Subterranean detectors

26. Get off the ground! Density perturbations  fluctuating gravitational
forces
You can’t walk but roller skates are fine
Seismic gravity gradient
When ambient seismic waves pass near and under an interferometric gravitational-wave detector, they induce density perturbations in the Earth, which in turn produce fluctuating gravitational forces on the interferometer’s test masses.
Human gravity gradient
The beginning and end of weight transfer from one foot to the other during walking produces the strongest human-made gravity-gradient noise in interferometric gravitational-wave detectors (e.g. LIGO). The beginning and end of weight transfer entail sharp changes (time scale ~20 msec) in the horizontal jerk (first time derivative of acceleration) of a person’s center of mass.

27. Cryogenic detectors

28. Beating down thermal noise
Intrinsic material loss
LCGT
I. Martin et al (2006)
Optical coatings

29. The best kind of squeezed state
In closing…
Very much in the future
Cryogenics
Subterranean or space observatories
Coming soon(er) to an observatory near you
Quantum radiation pressure manipulation
Squeezing
The best kind of squeezed state

30. The best kind of squeezed states

31. Tomorrow White Mountains All are invited
Annual Lab Hike
Tomorrow
White Mountains All are invited