Gravitational Waves: Sources and Detection · 2016-11-15 · Gravitational Waves: Sources and...

Gravitational Waves: Sources and Detection

Nergis MavalvalaDepartment of Physics

Massachusetts Institute of Technology

Les Houches, August 2015

Lecture #1

Outline

Lecture 1

Gravitational wave (GW) basics

Sources and emission strength

Interferometric GW detectors

Conceptual ideas to actual realizations

Fundamental noise sources

First astrophysical searches

Lecture 2

Second‐generation detectors (currently under

construction)

Key technologies

Major challenges

Outline

Lecture 3

Third‐generation detectors

Quantum technologies

Squeezed states of light

Optomechanics (classical and quantum)

Gravity’s messenger

Understanding gravity

Newton (16th

century)

Universal law of gravitation

Worried about action at a

distance

Einstein (20th

century)

Gravity is a warpage of

space‐time

Matter tells spacetime how

to curve spacetime tells matter how to move

1 22

Gm mFr

4

8 GG Tc

Newton vs. Einstein

K. Glampedakis

GWs in linear gravity

For weak gravitational fields, flat spacetime (Minkowski metric) is perturbed (h)

GR field equations in vacuum reduce to a wave equation

Plane wave solution in weak gravity: transverse wave with two polarizations (+ and x)

Metric perturbation and strain

Minkowski metric in Cartesian coordinates

Linearized perturbation in transverse traceless gauge

Space‐time interval

Quadrupole formula

Derived by Einstein in 1918 by solving linearized field equations with a source term

Accurate for all sources as long as wavelength is much longer than source size R

Generalized source strength

GWs carry energy

The stress‐energy carried by GWs

Stress energy is not localized; a certain amount of stress‐ energy is contained in a region of the space which extends

over several wavelengths

The luminosity is the integral of the stress‐energy tensor over the area of that region of space

This gives

Astrophysical sources of GWs

GW luminosity

Sources need to be compact (R

≈

RSch

) and relativistic (v

≈

c)Lots of compact mass (neutron stars, black holes) Rapid acceleration (orbits, explosions, collisions)

Colliding compact starsBinary NS and BH

Supernovae

The big bangEarliest moments

The unknownLooking back in time

CMB 400 thousand

years

Now 13 billion

years

GWs 0 years

where

A bit of history

Gravitational radiation was first introduced by Einstein in 1916 in his seminal paper on General Relativity

In a subsequent paper in 1918 Einstein gave the first correct

formulation of gravitational waves

But he himself remained uncertain (not just of how immeasurably weak

they are, but of their very existence)

Submitted a retraction in a paper

with Rosen in 1937

Retracted the retraction after

discussion with Infeld and Robertson

Doubts and controversy finally subside after 1957

Experiment and observation have the final say (as usual) …

Gravitational waves ‐‐

the Evidence

PSR 1913 + 16

Two neutron stars orbiting each other at 0.0015c

Compact, dense, fast relativistic system

Emit GWs and lose energy

Used time of arrival of radio pulses to measure change in orbital period due to GW emission

Hulse & Taylor’s Binary Neutron Star System(discovered in 1974, Nobel prize in 1993)

Signal strength of binary pulsars

In our galaxy (21 thousand light years away, 8 kpc)

h ~ 1018

In the Virgo cluster of galaxies (50 million light

years away, 15 Mpc)

h ~ 1021

Typical binary pulsar at the end of its lifetime (100 million years from now)

M M

r

R

30

23

10 kg20 km200 Hz

10 m

MRfr

Effect on test particles

Place a pair of test particles at distances ±

x0

from the origin of a Cartesian coordinate system

Assume GW traveling in +z‐direction

Separation between particles given by

Similarly, for a pair of particles on the y‐axis

Key properties of GWs

Ripples in space‐time or propagating curvature perturbation

Propagate at speed of light

Stretch and squeeze the space transverse to

direction of propagation

Amplitude falls as 1/r

Two polarizations (+ and x)

Lowest allowed multipole is quadrupole

Emitted

by

compact rapid accelerating masses

Astrophysics with GWs vs. Light

Very different information, mostly mutually exclusive

Difficult to predict GW sources based on EM observations

Light GWAccelerating charge Accelerating mass

Images (pretty pictures) Waveforms (pretty sounds)

Absorbed, scattered, dispersed by matter

Very small interaction; matter is transparent

100 MHz and up 10 kHz and down

Gravitational wave detection using precision interferometry

Simple concept, challenging implementation

Make mirrors that are very still

Vibration isolation and thermal fluctuation control

Probe the mirror positions using laser light

Ultra-high precision optical measurement

Manipulate quantum fluctuations of the light

LaserLaser

GW detector at a glance

Optical cavities•

Mirrors facing each other

•

Builds up light powerLots of laser power P• Signal α

P

• Noise α10 W

20 kW

P

4 km

Mirrors hang as pendulums•

Quasi-free particles

•

Respond to passing GW•

Filter external force noise

Global network of detectors

GEO600 (HF)2011

Advanced LIGO Hanford 2015

Advanced LIGO Livingston 2015

Advanced Virgo2015 LIGO-India

2022

KAGRA2017

Why a global network?

Angular response is pure quadrupole

Nearly omni‐directional

Earth transparent to GW

Pinpoint sources in sky by triangulation

Localization depends strongly on

SNR and number of detectors

Large duty factor (fraction of time the network has high sensitivity)

Need five sites to get 4 detectors

operational ~85% of the time

Localization with LIGO and Virgo

Localization with LIGO, Virgo and India

10 kg Fused Silica25 cm diameter

10 cm thick

21

1810 4000

~ 10 meters

GWL h L

First phase of LIGO

Shot noiseSNR Power

Seismic noise

Thermal noise

End of lecture 1

We ended with the Initial LIGO noise curve. Tomorrow we will pick up where we left off, starting with limiting noise sources, and

moving on to Advanced LIGO.

Essential or helpful readings and viewings

General Relativity (GR) and Gravitational Waves (GWs)

Einstein (1916): Annalen

der

Physik

49, 769–822 (1916)

Schutz

(1984): Gravitational waves on the back of an envelope, Am. J. Phys. 52, 412

Cutler and Thorne (2002): http://arxiv.org/pdf/gr‐qc/0204090v1.pdf

Astrophysical sources and rates (2010): CQG 27, 173001

Caltech graduate course on GWs: Physics 237 http://elmer.tapir.caltech.edu/ph237/

GR meets precision laser interferometry

Weiss, RLE Report (1972): http://www.hep.vanderbilt.edu/BTeV/test‐

DocDB/0009/000949/001/Weiss_1972.pdf

Saulson book (1990): Fundamentals of interferometric gravitational wave detectors, Singapore Press

Fritschel/LSC (2015): “Advanced LIGO,”

Class. and Quant. Grav. 32, 074001 (http://lanl.arxiv.org/pdf/1411.4547.pdf)

http://www.hep.vanderbilt.edu/BTeV/test-DocDB/0009/000949/001/Weiss_1972.pdf

http://www.hep.vanderbilt.edu/BTeV/test-DocDB/0009/000949/001/Weiss_1972.pdf

Low frequency noises (<100 Hz)

Vibration isolation

Matichard review (2015):

http://authors.library.caltech.edu/56793/2/1407.6377v1.pdf

Mirror suspensions

Shapiro Ph.D. thesis (2014)

Squeezed film damping

Vitale et al. (2012)

Martynov Ph.D. thesis

Seismic noise regression

Driggers et al. PRD 86, 102001 (2012)

Thermal noise

Callen and Welton (1951): Phys. Rev. 83, 34

Saulson (1990): PRD 42, 2437

Harry, Bodiya and DeSalvo (2012): Optical coatings and thermal noise in precision measurement, Cambridge U. Press

Steinlechner et al. (2015): PRD 91, 042001

Yam et al. (2015): PRD 91, 042002

Quantum optics in GW detectors

Caves (1980): PRL 45, 75

Caves (1980): RMP 52, 341

Caves (1981): PRD 23, 1693

Kimble et al. (2001): PRD 65,

Schnabel et al. review (2010): Nat. Comm

McClelland et al. review (2011): Lasers and Photonics

LIGO Scientific Collaboration (2012): Nature Physics

LIGO Scientific Collaboration (2013): Nature Photonics

Optomechanics in GW detectors

Braginsky et al. (1967 and 1970): JETP 25, 30

and 31

Caves (1980): PRL 45, 75

Caves (1980): RMP 52, 341

Caves (1981): PRD 23, 1693

Buonanno and Chen (2002): PRD 65, 042001

Y. Chen review (2013): http://arxiv.org/pdf/1302.1924.pdf

http://arxiv.org/pdf/1302.1924.pdf

Optomechanics experiments in GW‐land

Sheard et al. (2004): PRA 69, 051801

Corbitt et al. (2006): PRA 74, 021802

Miyakawa et al. (2006): PRD 74, 022001

Corbitt et al. (2007): PRL 98, 150802 and PRL 99,

LIGO Scientific Collaboration (2009): NJP

Neben et al. (2012): NJP 23, 1693

Buonanno and Chen (2002): PRD 65, 042001

Y. Chen review (2013): http://arxiv.org/pdf/1302.1924.pdf

http://arxiv.org/pdf/1302.1924.pdf

Advanced Gravitational Wave Detectors




Lecture #2

First phase of LIGO

Shot noiseSNR Power

Seismic noise

Thermal noise

Limiting Noise Sources

Dissecting noise sources

Limiting noises

Seismic noise

Direct coupling

Newtonian noise

Thermal noise

Suspension Brownian

motion

Optical coatings

Mirror internal

Quantum noise

Shot noise

Radiation pressure noise

Other technical noises

Laser frequency

Laser intensity

Scattered light

Residual gas

Length and alignment control

systems

Magnetic actuation

Acoustic couplings

Nonlinear couplings (up‐

conversion …

Seismic noise

Mechanical oscillators (pendulums)

FROM

TO

Isolation~1/f2

x/F

Vibration isolation

Thermal noise

Fluctuation‐Dissipation Theorem

Response of any linear system in thermodynamic equilibrium

Brownian noise or Johnson noise

Fluctuating force spectrum is proportional to magnitude

of dissipation (mechanical loss)

HEAT BATH

Fluctuation-Dissipation TheoremCallen and Welton, 1951

LOSS

Motion

Menagerie of thermal noises

Mirror substrate

Suspension

Optical Coating

Anelasticity of materials

Pendulums are special

Pendulums can achieve much higher Q

than intrinsic material loss φ‐1

would imply

For vertical displacements, response due to elastic spring constant of wire stretching (with spring constant

)

For horizontal displacements, response due to gravitational restoring force (with spring constant

)

Only elastic spring constant has dissipative part, gravitational potential is lossless

The Quantum Noise Limit

Quantum Noise in an Interferometer

X1

X

X1

X

Laser

Radiation pressure noiseCoherent intracavity field + quantum fluctuations

fluctuating force mirror displacement

Shot noiseCoherent signal field + quantum fluctuations

fluctuating phase

First phases of LIGO (2000 to 2011)

Not Fast or Easy

Started in 2001…Many years and many technical noises later, we arrived at the design.

Sensitivity achieved during S6/VSR1 (2007 to 2010)

LIGO: H2

LIGO: L1

LIGO: H1

Virgo

GEOLIGO, GEO and Virgo share all data to form a global detector network.

Since 2006, roughly 2 years of network data have been collected.

The LIGO Scientific Collaboration includes over 50 Universities and about 1000 researchers.

LIGO listened… And had something to say

Astrophysics with first generation detectors

Journals include

Physical Review

Astrophysics Journal

Nature

Classical and Quantum

Gravity

New Journal of Physics

Topics include

Neutron star and black

hole coalescence

Gamma‐ray bursts

Known pulsars (e.g . Crab)

Unknown pulsars

Transient sources

(“bursts”)

Cosmological stochastic

background

Over 100 published results

No positive detections (yet)

The search for GRB070201

DM31

Abbott et al., Ap. J 681, 1419 (2008)Mazets et al., Ap. J 680, 545 (2008)Ofek et al., Ap. J 681, 1464 (2008)

25%50%75%90%

GRB 070201

Very luminous short duration, hard

gamma‐ray burst

Detected by Swift, Integral, others

Consistent with being in M31

Leading model for short GRBs:

binary merger involving a neutron star

Looked for a GW signal in LIGO

No plausible GW signal found

Can say with >99% confidence

that GRB070201 was NOT caused by a compact binary star merger in M31

Conclusion: it was most likely a Soft Gamma Repeater giant flare in M31

Why we didn’t hear anything yet?

Extrapolate NS‐NS inspirals to other galaxies weighted by blue‐light luminosity

Roughly 1 MW of blue‐light every 20 Mpc3

Events ~ Rate x Time x Detection Volume

?Estimated by population synthesis based on 5 know tight NS binaries Rate ~ 100/Myr

Second generation detectors

Advanced LIGO

Astrophysical motivations

Factor 10 better amplitude sensitivity

(Range)3

= rate

Factor 4 lower frequency bound

Use same infrastructure but replace detector

components with new designs

Expect to observe 1000x more galaxies by 2018

Facilities limits

Seismic noise: better isolation

10-24

10-23

10-22

10-21

10Hz 100Hz 1kHz 10kHz

Seis

mic

Strain1/√Hz

Thermal

Quantum

Each interferometer floats on tons of metal with hundreds of active control loops…

Active Isolation, 3 layersQuadruple Pendulum, 1Hz

Courtesy Matt Evans

Thermal noise: Less Loss

Strain1/√Hz

10-24

10-23

10-22

10-21


Thermal

Quantum

Quartz Suspension, Q ~ 600 MFused Silica Test Mass, 40 kg

It all ends in a 40 kg glass cylinder suspended by 400 μm glass fibers…

Courtesy Matt Evans

Shot noise: More power

10-24

10-23

10-22

10-21


Quantum

Strain1/√Hz

100 W input power5 kW on beam splitter750 kW in arm cavities

With nearly 1MW of circulating power, radiation pressure becomes a serious problem…

13um !!

Courtesy Matt Evans

More Power, Less Loss…Some woes!

NascentExcitation

MechanicalMode

RadiationPressure

PumpField

ScatteredField

(cavity gain)

High FinesseCavity

Courtesy Matt Evans

Instabilities from photon-phonon scatteringA mirror phonon can be absorbed

by the photon, increasing the photon energy

dampingThe photon can emit

the phonon, decreasing the photon energy acoustic instability

absorption emissionPhononPhonon

Damping Unstable oscillation

Advanced LIGO – here and now

Advanced LIGO noise budget

Advanced LIGO prepares for O1

Noise hunting

Advanced LIGO (2011…)

Radiation pressure noiseStronger measurement larger backaction

Shot noiseMore laser power

stronger measurement

Beyond Quantum Noise

Lecture 3

Quantum engineering

Quantum noise in an interferometer

X1

X

Laser

X1

X

Radiation pressure noiseCoherent intracavity field + quantum fluctuations

fluctuating force mirror displacement

Shot noiseCoherent signal field + quantum fluctuations

fluctuating phase

Squeezed state generation

How to squeeze photon states

Need to simultaneously amplify one quadrature and

de‐amplify the other

Create correlations between the quadratures

Simple idea nonlinear optical material where

refractive index depends on intensity of light illumination

Nonlinear optical interaction

a

a

a

a bb

Parametric oscillation Second harmonic generation

The output photon quadratures are

correlated

a

b

Parametric amplification

a

a

a

Squeezed light source

To Inter- ferometer

Squeezed state injection

Squeezing injection in LIGO

PowerRecycling

Mirror

H1 LASER

Anti-Symmetric Port

Arm Cavity (4 km)

V1

CONTROLLASER

PUMP LASER

SHG

Squeezed vacuum source

Output Photodiode

OMC

OPO

Vacuum Envelope

to squeezed light source: feed-back to PUMP laser frequency

for squeeze angle control

LIGO H1 Interferometer

Input Mode-Cleaner frequency shiftedcontrol beam

BeamSplitter

Arm Cavity (4 km)

FaradayIsolator

Output ModeCleaner

squeezed vacuum &frequency shifted control beam

(a) Coherent state of light

Quadrature Phase

In-Phase

(b) Vacuum state

In-Phase

(c) Squeezed vacuum state

In-Phase

OPO green pump beam

to squeezed light source:phase lock loop with PUMP laser

from H1 laser:phase lock loop with PUMP laser

from squeeze angle control photodiode: feed-back to PUMP

laser frequency

Squeeze Angle Control Photodiode

Quadrature Phase

Quadrature Phase

LIGO H1 Squeezed

Squeezing down to 150 Hz

2 dB (25%) improvement

LIGO Scientific Collaboration, Nature Photonics (2013)

Advanced LIGO with squeeze injection

Shot noise

Radiation pressure

McClelland, Mavalvala, Schnabel, and Chen, Lasers and Photonics Reviews (2011)Schnabel, Mavalvala, McClelland, and Lam, Nature Communication (2010)

Frequency dependent squeezing

Filter cavity

Frequently asked questions

If the GW changes the space‐time distance, doesn’t the wavelength of the light also change in the same way?

How do we know GWs

even exist? What if GR is wrong?

What are the best estimates and uncertainties for known and/or expected astrophysical sources?

Space detectors are so difficult and expensive. Why not just stick with terrestrial detectors?


Why don’t we just make the interferometers longer?

How flat do the mirrors have to be? Does the technology exist to make a mirror surface as exquisite

as the interferometer path length changes of 10‐18

m?

If the mirrors are moving by many microns, how can we measure length changes of 10‐18

m?


If thermal noise is such a big problem, why not cool the mirrors?

If Newtonian noise is such a big problem, why not measure and subtract it?

Isn’t it hopeless to do better than Advanced LIGO? After all, how can you circumvent the Heisenberg

Uncertainty limit?

Optomechanics in LIGO




Lecture #3

Squeezed state generation

Nonlinear optical interaction

Squeezed light source

To Inter- ferometer

Squeezing injection in LIGO

PowerRecycling

Mirror

H1 LASER

Anti-Symmetric Port

Arm Cavity (4 km)

V1

CONTROLLASER

PUMP LASER

SHG

Squeezed vacuum source

Output Photodiode

OMC

OPO

Vacuum Envelope

to squeezed light source: feed-back to PUMP laser frequency

for squeeze angle control

LIGO H1 Interferometer

Input Mode-Cleaner frequency shiftedcontrol beam

BeamSplitter

Arm Cavity (4 km)

FaradayIsolator

Output ModeCleaner

squeezed vacuum &frequency shifted control beam

(a) Coherent state of light

Quadrature Phase

In-Phase

(b) Vacuum state

In-Phase

(c) Squeezed vacuum state

In-Phase

OPO green pump beam

to squeezed light source:phase lock loop with PUMP laser

from H1 laser:phase lock loop with PUMP laser

from squeeze angle control photodiode: feed-back to PUMP

laser frequency

Squeeze Angle Control Photodiode

Quadrature Phase

Quadrature Phase

LIGO H1 Squeezed

Squeezing down to 150 Hz

2 dB (25%) improvement

LIGO Scientific Collaboration, Nature Photonics (2013)

Advanced LIGO with squeeze injection

Shot noise

Radiation pressure

McClelland, Mavalvala, Schnabel, and Chen, Lasers and Photonics Reviews (2011)Schnabel, Mavalvala, McClelland, and Lam, Nature Communication (2010)

Frequency dependent squeezing

Filter cavity

Oelker Isogai et al. (2015)Extrapolation for Adv. LIGO:

16m filter cavity: factor of 2 reduction in shot noise (6dB),

25% reduction in radiation pressure noise (2 dB)

Optomechanics & Radiation Pressure

Radiation Pressure

When radiation pressure dominates

Techniques for improving gravitational wave detector sensitivity

Opportunities to study quantum effects in macroscopic systems

Observation of quantum radiation pressure

Generation of squeezed states of light

Quantum states preparation

Tools for quantum information science

Cavity Optomechanics Primer

Cavity optomechanics

F. Marquardt, Les Houches “Quantum Machines”

(2011)

Linearized approximation

Optomechanical Coupling

Laser-driven cavity mode at frequency ∆

Mechanical oscillator mode at frequency Ω

and

are experimental “knobs”

Coupled oscillators with coupling coefficient g(α, ∆)

Optomechanical Phenomena

On resonance (Δ

= 0)

Optical state phase shift

proportional to displacement

Blue detuning (Δ

= + Ω)

Two‐mode squeezing

Optical spring

Mechanical lasing / Parametric instabilities

Red detuning (Δ

= ‐

Ω)

State transfer between

photons and phonon

Optical damping

Cooling

Imbalance of Stokes and anti‐Stokes

Aspelmeyer, Kippenberg, and Marquardt, 1303.0733

Stokes scattering enhanced

Anti-Stokes scattering enhanced

Scattered photons have less energy

heating/amplification of mechanical mode

Scattered photons have more energy

cooling/damping of mechanical mode

Explosion of optomechanics experiments

PC zipper 1012

g

SiN3

membrane 108

g

Toroidal microcavity 1011

g

Micromirrors 106

g

12mm mirror 1 g

LIGO mirror 104

g

AFM cantilevers 108

g

WG-WGM 1011

g

Trampolines 107

g

NEMS 1011

g

Optomechanics in LIGO

The radiation pressure force couples the light field to mirror motion

Alter the dynamics of the mirror

Spring‐like forces optical trapping and acoustic instability

Viscous forces optical damping

Tune the frequency response of the GW detector

Manipulate the quantum noise

Quantum radiation pressure noise and the standard quantum

limit

Produce quantum states of the mirrors

Produced squeezed states of light

Clas

sica

lQ

uant

um

Classical forces in optomechanics

Detune optical field from cavity resonance

Change in mirror position changes intracavity power radiation pressure

exerts force on mirror

Time delay in cavity results in cavity

response doing work on mechanics

Optomechanical coupling in Adv. LIGO

750 kW in arm cavities gives large static force 3 mm displacement from equilibrium

Signal recycling cavity may be detuned to optimize interferometer response to GW sources

Detuned cavity equation of motion

Optomechanical rigidity gives harmonic restoring force with spring constant

Optomechanics in Adv. LIGO

SQL

Source‐specific tuning

23

10-24

10-23

10-22

10-21

10-20

10-19

Stra

in (1

/Hz)

1012 3 4 5 6 7 8 9

1022 3 4 5 6 7 8 9

1032 3 4 5 6 7 8 9

104

Frequency (Hz)

Hanford 4 km S6

Livingston 4 km S6

AdvLIGO, No Signal Recycling (early operation)

AdvLIGO, Zero Detuning (Low Power)

AdvLIGO, ZeroDetuning (High Power)

AdvLIGO, NS-NS optiimized AdvLIGO, High Frequency Detuning

Targeting different sources

24

101

102

103

10−2

4

10−2

3

10−2

2

Frequ

ency

[Hz]

Strain [1/Hz]

Adva

nced

LIGO

: Nom

inal

LMXB

SN

NS EOS

Binary Populations Tests of GR

IMBH

Pulsars

Multi-messenger (sky localization)

Courtesy

Matt Evans

Primordial GWB

Parametric instability

Damping and oscillation

Mirror phonon absorbed by photon decreases phonon

energy damping

Photon emitted by mirror phonon increases phonon energy acoustic instability

(unstable oscillation)

absorption

emission

Phonon

Phonon

High optical power, low mech. loss

NascentExcitation

MechanicalMode

RadiationPressure

PumpField

ScatteredField

(cavity gain)

High FinesseCavity

Courtesy Matt Evans

Acoustic instability in Adv. LIGO

12, , nnmmarmm GBQPR

mechanical modeQ-factor

power in arm cavity

spatial overlap optical-

mechanical mode

optical mode gain

optical mode linewidth

frequency match

Evans et al., PRL 114, 161102 (2015)

Approaching the quantum regime

Three scales on which we study quantum light‐mirror coupling

250 ng 1 g 10 kg

Gram‐scale mirrors

Experimental cavity setup

5 W

10%

90%

1 gram mirror

Optical fibers

Coil/magnet pairs for actuation (x5)

1 m

All‐optical trap

Blue detuned field gives optical spring (trap)

Red detuned field with 1/20 the power gives damping

Independently control restoring and damping forces

T. Corbitt et al., Phys. Rev. Lett 98, 150802 (2007)

Stable!

Stiff!

Eliminate frequency noise

Two identical cavities with 1 gram mirrors at the ends

Common‐mode rejection cancels out laser noise

T. Corbitt et al., Phys. Rev. A 73, 023801 (2006)

Optically trapped and cooled mirror

C. Wipf, T. Bodiya, et al. (March 2010)

1 gram mirror

Optical fibers

Teff

= 0.8 mK N = 35000

Optical dilution of thermal noise

Optical spring couples mechanics to “cold”

bath

Detailed balance:

Environment T ~ 300 K

Mechanics Teff

Laser T ~ 0 K

Kilogram scale mirrors

Thomas Corbitt Chris Wipf Daniel Sigg

Cooling the kilogram‐scale mirrors of Initial LIGO

LIGO Scientific Collaboration

Observations of QRPN and OM squeezing

Quantum radiation pressure and optomechanical squeezing observed

QRPN observed (2013)

Regal group, ColoradoNature Physics (2013)

Thermal noise

Rad

iatio

n pr

essu

re

Optomechanical squeezing (Caltech)

Painter group, CaltechNature (2013)

Optomechanical squeezing (Boulder)

Regal group, ColoradoPhys. Rev. X (2013)

Beyond Advanced LIGO

Advanced LIGO/Virgo Upgrades

Newtonian noise subtraction

Seismometer array

around test masses

2 to 3x reduction at few

Hz


10 dB (3x) squeezing at

source

6 dB (2x) SNR improvement

realizable

Quantum noiseCoating Brownian noiseNominal aLIGOFrequency IndependentTotal Noise

Third generation detectors

Einstein TelescopeCosmic Explorer

Many options to consider…

10 to 40 km arm lengths

Underground caverns,

salt mines

Newtonian noise subtraction

factors of ~2 achieved

Mirrors cooled to 4 K

Vibrations worrisome

Silicon optics

200kg chunks

low mechanical loss

high thermal conductivity at low temp.

Xylophone

Low frequency cryogenic, low laser power

High frequency high laser power

Squeezed light injection

10 to 20 dB !

Cast of Characters > 900

Capturing the elusive wave…

Tests of general relativity

Directly observe ripples of

space‐time

Astrophysics

Directly observe the Black Holes, the Big

Bang, and objects beyond our current imagination

Fertile ground for quantum optics and optomechanics

at very macroscopic objects

40 kg

Gravitational Waves: Sources and Detection · 2016-11-15 · Gravitational Waves: Sources and...

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Transcript of Gravitational Waves: Sources and Detection · 2016-11-15 · Gravitational Waves: Sources and...