1. Gravitational wave detection and the quantum limit
The LIGO Laboratory
Nergis Mavalvala
MIT grad open house, April 2009

2. Activities of the LIGO Lab
Gravitational wave detectors
Initial LIGO (2000 – 2007)
Enhanced LIGO (2007 – 2010)
Advanced LIGO (2011 – …)
Searches for astrophysical sources
Transient sources
Continuous sources
Quantum mechanics
Of light
Of large objects (macroscopic scales)

3. Gravitational wave basics
Gravitational Waves “Ripples in spacetime fabric”
Stretch and squeeze the space transverse to direction of propagation
Strain
Emitted by aspherical accelerating masses
Expected strain ~ 10-21
Laser
Photodetector
Laser
Photodetector
L+DL L
“What better way to get at the juicy stuff than to shine a laser at it” Eric Cornell (June 25, 2007, ICOLS)

4. Global network of detectors
GEO
VIRGO
LIGO
TAMA
AIGO
LIGO
Detection confidence
Source polarization
Sky location
LISA

5. Astrophysical searches
Coalescence of binary compact objects (neutron stars, black holes, primordial BH)
Core collapse supernovae
Black hole normal mode oscillations
Neutron star rotational instabilities
Gamma ray bursts
Cosmic string cusps
Periodic emission from pulsars (esp. accretion driven)
Stochastic background (incoherent sum of many sources or very early universe)
Expect the unexpected!
Transient
Campanelli et al., Lazarus Project
GWs
neutrinos
photons
now
High duty cycle

6. Generations of detectors
Initial LIGO Enhanced LIGO Advanced LIGO

7. Advanced LIGO (2011)
Initial LIGO
Enhanced LIGO
Advanced LIGO

8. Radiation pressure noise More laser power  stronger measurement
Advanced LIGO Quantum noise everywhere
Radiation pressure noise
Stronger measurement  larger backaction
Shot noise
More laser power  stronger measurement

9. What our students do LIGO instrument science
Make LIGO detectors work
Design and test future improvements
Look for astrophysical sources in LIGO data
Targeted pulsars (known period and location)
(Un)modeled bursts
Explore the fundamental quantum limits
Improvements using sub-quantum states of light
Optical trapping and cooling of mirrors (path to quantum states of macroscopic objects)

10. What our group is like At work…

11. What our group is like At play…

12. Join our quest to… Detect gravitational waves Beat quantum noise limits and have a blast doing it