GEO600: The First Application of Squeezed Light

GEO600: The First Application of Squeezed Light

Roman Schnabel, for the GEO600 group, the Quantum Interferometry Group, and the LSC

Albert-Einstein-Institut (AEI)

Institut für Gravitationsphysik

Leibniz Universität Hannover

Albert - Einstein- Institut R. Schnabel, LaThuile 2011, March 23 2

Outline

• Introduction to Squeezed Light

• The first squeezed-light laser for GW detectors

• Sensitivity improvement of GEO600 with squeezed light

• Squeezed light as a key-technology for GW astronomy

Albert - Einstein- Institut R. Schnabel, LaThuile 2011, March 23

Gravitational Waves

Merging neutron stars. Numerical relativity simulation of gravitational waves emitted from two neutron stars which are about to merge in 4 ms [Rezzolla, AEI].

3

h:

Gravitational wave astronomy requires observatories that can detect h < 10-23 (over a band from e.g. 100Hz - 200Hz)


Laser

50%

Bea

m

splitt

er

Gravitational Wave Detection

Mirror 1

Mirror 22) Laser light

> km

3) Interference

4) Photo-electric effect

Photo diode

4

Photo-electric currentmodulated at GW frequency

1) Test masses


Photo-Electric Current

Time intervals

Ph

oto

ns p

er

time

inte

rval

5

N

(No signal, but photon shot noise)



6

Time intervals

Ph

oto

ns p

er

time

inte

rval

N

(GW signal?)


Photon Counting Statistics

Coherent state

€

⇒ ˆ N = N = α2

=10000

Photon number N

Pro

babi

lity

[re

l. un

its]

7

NNNN

N

€

α =100

€

~1

N ~

1

PLaser

Relative shot-noise


Increasing the Light Power

High power laser

Mirror 1

Mirror 2

Photo diode

Photo-electric current

Heating by light absorption

8

Power-recycling mirror


Is there a possibility to increase the signal/quantum noise–ratio without increasing the laser power?

9

Yes, by squeezed laser light!


Shot-Noise in an Interferometer

Laser

Photo diode

Beam splitter

Mirror

[Caves, Phys. Rev. D 23, 1693 (1981)]

Due to zero point fluctuations(vacuum noise)


Laser

11

Squeezing the Shot-Noise

Photo diode

Beam splitter

MirrorC. M. Caves (1981):Reduction of quantum noise with squeezed light

[Caves, Phys. Rev. D 23, 1693 (1981)]

Squeezed light laser

FaradayRotator


Squeezing factor: 3 dB

Squeezing factor: 10 dB

“Squeezed” Counting Statistics

Photon number N

Pro

babi

lity

[re

l. un

its]

12

Noise squeezing



Time intervals

Ph

oto

ns p

er

time

inte

rval

13

N

(No signal)


Photo-Electric Current - Squeezed

Time intervals

Ph

oto

ns p

er

time

inte

rval

14

N

Squeezing the noise of a random process without a measurement!?

Quantum mechanics:Squeezing requires time/energy (and amplitude/phase quadrature) entangled photons


Squeezing in the Wave Picture

X1

X2 cc

c

+

+

+

+

15

Quadrature squeezing at sideband frequency


The GEO600 Squeezed Light Laser

16


Standing wave cavity

Generation of Squeezed Light (PDC)

2-nonlinear crystal:MgO:LiNbO3

Pump field inputPump field input(cw, 532nm)(cw, 532nm)

Squeezed field outputSqueezed field output(cw, 1064nm) by parametric (cw, 1064nm) by parametric down-conversion (PDC) down-conversion (PDC)


History of Squeezed Light Generation

First squeezed light: [Slusher et al., PRL 55, 2409 (1985)]

Research labs with squeezed light (not complete):

- Kimble (CalTech): teleportation: [Furuzawa et al., SCIENCE 282, 706 (1998)]

- Grangier (Orsay); kitten: [Ourjoumtsev et al., SCIENCE, 312, 83 (2006)]

- Schiller and Mlynek (Konstanz): tomography: [Nature 387, 471 (1997).]

- Bachor and Lam (Canberra): 6dB at 1064nm [J. Opt. B 1, 469 (1999).]

- Leuchs (Erlangen); ~7 dB pulsed [Opt. Lett. 33, 116 (2008).]

- Polzik (Copenhagen), [Neergaard-Nielsen et al., PRL 97, 083604 (2006)]

- Furusawa (Tokyo); 9 dB: [Takeno et al., Opt. Express 15, 4321 (2007).]

- Fabre (Paris), Zhang, Peng (Shanxi);

- Andersen (Copenhagen); Mavalvala (MIT),...

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History of Squeezed Light Generation

Research & development towards the first application of squeezed light

- McClelland (ANU), power-recycling [McKenzie et al., PRL 88, 231102 (2002)]

- McClelland (ANU), audio-band [McKenzie et al., PRL 93, 161105 (2004)]

- RS (LUH), signal-recycling [Vahlbruch et al., PRL 95, 211102 (2005)]

- RS (LUH), control scheme [Vahlbruch et al., PRL 97, 011101 (2006)]

- RS (LUH), full band-width [Vahlbruch et al., New Journal of Phys. 9, 371 (2007)]

- Mavalvala (MIT), suspended mirrors [Goda et al., Nature Phys. 4, 472 (2008)]

- RS (LUH), 10dB [Vahlbruch et al., PRL 100, 033602 (2008)]

- RS (LUH), turn-key source [Vahlbruch et al., CQG 27, 084027 (2010)]

Recent review:

[R.S. et al., Nature Comm. 1:121 doi: 10.1038/ncomms1122 (2010)]

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Transport to the GEO600 GW Detector

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GEO600: Squeezed Light in Application

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Observatory noise without squeezed light

With squeezed light


Laser

22

Squeezing the Shot-Noise (SN) and the Radiation Pressure Noise (PRN)

[Kimble et al., Phys. Rev. D 65, 022002 (2001)]

Squeezed light laser

FaradayRotator

[Jaekel and Reynaud, Europhys. Lett. 13, 301 (1990)]

Filter cavities


(SQL)

Shot noise

Radiation pressure

noise

[Jaekel, Reynaud 1990]

QND-Regime

Squeezing SN and RPN

Squeezed Light Input (8dB)


Summary

• GEO600 now uses squeezed light and achieves its best ever sensitivity (at shot-noise limited frequencies)

• A real application of entangled photons in squeezed light has been realized

• Squeezing is mature and might become a key-technology in all future GW observatories, such as ET

GEO600: The First Application of Squeezed Light

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