2445-03 Advanced Workshop on Nanomechanics Tom Purdy 9 - 13 September 2013 JILA - NIST & University of Colorado U.S.A. Quantum Measurement in an Optomechanical System
2445-03
Advanced Workshop on Nanomechanics
Tom Purdy
9 - 13 September 2013
JILA - NIST & University of Colorado U.S.A.
Quantum Measurement in an Optomechanical System
Tom Purdy, JILA – NIST & University of Colorado with Bob Peterson, Ben Yu, Nir Kampel, Alec Jenkins, Cindy Regal
T P d JILA NIST & U i it f Ci iti l dl d
1
10
100
0.01 0.1 1 10 100
SQL
Thermal Motion
Measurement Laser Power
Pos
ition
Unc
erta
inty
1.0
0.8
0.6 1.56 1.54 1.52 1.50
Range of Optomechanical Systems Big Small
10 kg 10 km 10 ng 1 mm 10-25 kg 10 nm
1 m
A. Kaufman, et al., PRX 2, 041014 (2012)
Ligo.caltech.edu
Ligo.caltech.edu
4 km
10-18 m
LIGO Membrane Optomechanics
Single Atom in Optical Tweezers
Sept. 9, 2013 Frontiers in Nanomechanics
Nanomechanics Macroscopic Systems
3
• Raman Sideband Cooling • Optical Tweezers • Electromagnetically
Induced Transparency
• High precision interferometry • Squeezed light • Quantum Nondemolition
Measurements
Big Small
10 kg 10 km 10 ng 1 mm 10-25 kg 10 nm Ligo.caltech.edu
4 km
10-18 m
LIGO Membrane Optomechanics
Single Atom in Optical Tweezers
Range of Optomechanical Systems
Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA
Nanomechanics Macroscopic Systems
Tom Purdy JILA 4
• Membrane Cavity Optomechanical System
• Raman Sideband Cooling • Introduction to quantum measurement • Observing quantum measurement
backaction • Using mechanical motion to measure
light • Building better mechanical resonators
Overview
Sept. 9, 2013 Frontiers in Nanomechanics
(1,1)
(2,2)
(4,4)
• Si3N4 dielectric membrane
• 0.5 mm X 0.5 mm X 50 nm
• High Tension ~ GPa
• High Mechanical Quality Factor
• MHz mechanical resonance frequencies
• 10% reflectivity, low optical absorption
• Low mass ~10 ng
Thompson, et al., Nature 452 72 (2008) Wilson et al., PRL 103 207204 (2009) Karuza, et al., NJP, 14, 095015 (2012) Purdy, et al., NJP, 14 115021 (2012)
Membrane Optomechanical System
Sept. 9, 2013 Frontiers in Nanomechanics
Verbridge, et al., JAP 99, 124304 (2006) Southworth, et al., PRL 102, 225503 (2009) Unterreithmeier, et al., PRL 105, 027205 (2010) Wilson-Rae, et al., PRL 106, 047205 (2011) Yu et al., PRL 108, 083603 (2012)
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Mirror Mirror
Membrane
Optical Intensity
Optical Frequency
Tran
smis
sion
Photodetector
Input laser
Mechanical Displacement Spectrum
Optomechanical Coupling
Sept. 9, 2013 Frontiers in Nanomechanics
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1”
Mirror
Piezoelectric Actuator
Membrane
Invar Spacer
• Compact, low vibration, low drift design
• Cryogenically compatible (4K flow cryostat)
• High optical finesse (<30,000)
• Low mechanical dissipation
small
4 K
Optomechanical Device
Sept. 9, 2013 Frontiers in Nanomechanics
8 0mn1mn
2mn
3mn
m
C
Anti-Stokes m = Mechanical frequency
m = Cavity frequency
= number of photons
mn = number of mechanical vibrational quanta
Raman Sideband Cooling
Laser Cooling
Sept. 9, 2013 Frontiers in Nanomechanics
Monroe…Wineland, PRL 75, 4011 (1995) Teufel, et al., Nature 475, 359 (2011) Chan, et al., Nature 478, 89 (2011) Tom Purdy JILA
9 0mn1mn
2mn
3mn
m
C
Anti-Stokes
Inpu
t Las
er
m
Optical Frequency
Raman Sideband Cooling
Laser Cooling
Sept. 9, 2013 Frontiers in Nanomechanics
Monroe…Wineland, PRL 75, 4011 (1995) Teufel, et al., Nature 475, 359 (2011) Chan, et al., Nature 478, 89 (2011) Tom Purdy JILA
Tom Purdy JILA 10
10-17 1.53 1.52 1.51
10-16
10-15
Frequency (MHz)
Total motion Thermal motion
Laser Cooling
Purdy, et al., NJP, 14 115021 (2012) Jayich, et al., NJP 14, 115018 (2012)
Sept. 9, 2013 Frontiers in Nanomechanics
Increasing Laser Power
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10-17 1.53 1.52 1.51
10-16
10-15
Frequency (MHz)
Laser Cooling
Purdy, et al., NJP, 14 115021 (2012) Jayich, et al., NJP 14, 115018 (2012)
Sept. 9, 2013 Frontiers in Nanomechanics
Increasing Laser Power
Tom Purdy JILA 12
Ligo.caltech.edu
2physics.com
Dis
plac
emen
t Spe
ctra
l D
ensi
ty N
oise
[m/H
z1/2]
Quantum Limits of Optical Detection
Sept. 9, 2013 Frontiers in Nanomechanics
Laser
Photodetector
Test mass
Test mass
Beamsplitter
~kg
Fundamental Sensitivity Limits: • Optical Shot Noise • Radiation Pressure Shot Noise
Limits theoretically identified decades ago, Caves, PRL 45 75 (1980) Unruh, Quant. Opt., Exp. Grav., and Meas. Th. (1982) Braginsky, et al., Science 209, 547 (1980) But little experimental work until recently LIGO, Nature Phys. 7, 962 (2011) Purdy, et al., Science 339, 801 (2013) Hertzberg, et al., Nature Phys. 6, 213 - 217 (2010)
Interferometric Gravitational Wave Detector: It’s like trying to infer the position of the moon by measuring the ocean’s tides, but 1015 times harder
W. Heisenberg, Physical Principles of the Quantum Theory (1930)
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Camera
electron
photon
Microscope
Heisenberg’s Microscope Thought Experiment
2/baimp px
Quantum Limits of Optical Detection
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Camera
electron
photon
Microscope
Heisenberg’s Microscope Thought Experiment
2/baimp px
Quantum Limits of Optical Detection
Standard Quantum Limit
1
10
100
0.01 0.1 1 10 100
Standard Quantum
Limit
Measurement Laser Power
Pos
ition
Unc
erta
inty
Shot Noise – statistical fluctuations of the
number of photons detected in a given time interval
Radiation Pressure Shot Noise – Randomly varying optical force fluctuations due to shot noise
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baimpFz SS
Quantum Limits of Optical Detection
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PD
PD PBS PBS
Mirror Mirror
Membrane
Signal Beam High Power (strong measurement) On resonance RPSN Displacement information imprinted in optical phase
Meter Beam Low Power Red detuned Optical Cooling Displacement readout
Meter Beam
Signal Beam
Optical Frequency F
Quantum Measurement Experiment Setup
Sept. 9, 2013 Frontiers in Nanomechanics
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Signal Beam OFF
Signal Beam ON
Dis
plac
emen
t Spe
ctru
m
as m
easu
red
by m
eter
bea
m
Radiation Pressure Shot Noise
Sept. 9, 2013 Frontiers in Nanomechanics
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1
10
100
0.01 0.1 1 10 100
SQL
Thermal Motion
Measurement Laser Power
Pos
ition
Unc
erta
inty
Purdy, et al., Science 339, 801 (2013) Murch, et al., Nature Physics 4, 561 (2008) Naik, et al., Nature 443, 193 (2006) John Teufel, unpublished
Radiation Pressure Shot Noise
Sept. 9, 2013 Frontiers in Nanomechanics
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Signal Beam Optical Power ( W)
Pos
ition
Unc
erta
inty
As
mea
sure
d by
the
Sig
nal B
eam
Approaching the Standard Quantum Limit
Sept. 9, 2013 Frontiers in Nanomechanics
Thermal Motion
SQL 1
10
1 10
20
3
2
1
0
(2,2) mode – well coupled
(4,4) mode – poorly coupled
Signal Beam Power 0
Radiation Pressure Shot Noise
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Recoil motion
1
10
100
0.01 0.1 1 10 100
Thermal Motion
Quantum Measurement of Light
Sept. 9, 2013 Frontiers in Nanomechanics
Quantum Noise Cancellation
1. Membrane senses signal beam intensity fluctuations 2. Meter beam reads out membrane displacement 3. Active feedback cancels signal beam intensity fluctuations
PD
PD PBS PBS
Meter Beam
Signal Beam
Intensity Modulator
Amp
FFG ,
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Wiseman and Milburn, PRA, 49:1350 (1994) Mancini and Wiseman, J. of Opt. B, 2:260 (2000) See also Haroche group Cavity QED work
Quantum Noise Cancellation
PD
PD PBS PBS
Meter Beam
Signal Beam
Intensity Modulator
Amp
FFG ,
1.2
1.1
1.0
0.9
0.8
1.52 1.51 1.50
8
6
4
2
0 1.52 1.51 1.50
(rel
ativ
e to
shot
noi
se) Meter Beam Signal Beam
23
Feedback ON
Feedback OFF
Quantum Noise Cancellation
Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 24
(Electronic Gain)
1.1
1.0
0.9
0.8 1 10 100
R=2.6 R=1.3 R=0.7
3
2
1
0 100 50 0
Signal Beam Power ( W)
R
RPSN to Thermal Force Ratio
Tom Purdy JILA 25
1.0
0.8
0.6
1.0
0.8
0.6
1.0
0.8
0.6
1.56 1.54 1.52 1.50
0.6
1.0
0.8
a
Self-Squeezing of Light
Purdy, et al., PRX, in press (2013) arXiv:1306.1268 Safavi-Naeini, et al., Nature 500, 185 (2013) Brooks, et al., Nature 488, 476 (2012)
Optical Frequency
Tran
smis
sion
Tom Purdy JILA 26
0.8
0.6
0.4
0.2
0.0
60 40 20 0
Thermal Noise
Quantum Efficiency
b
1.0
Self-Squeezing of Light
Purdy, et al., PRX, in press (2013) arXiv:1306.1268 Safavi-Naeini, et al., Nature 500, 185 (2013) Brooks, et al., Nature 488, 476 (2012)
Optical Frequency
Tran
smis
sion
Self-Squeezing of Light
1.2
1.1
1.0
0.9
0.8
2.5 2.0 1.5 1.0
(rel
ativ
e to
shot
noi
se)
(1,1) (1,2) (2,2)
(1,3) (2,3) (2,4)
(3,4) (1,5)
(2,5)
Self-Squeezing of Light
inI
inQ
outQ
inI
outI
rXXX
XX
Nonlinear Optics: Complex Kerr Medium Self Phase Modulation Squeezed Light
quadrature phase
quadratue amplitude
Q
I
X
X
sincos QI XXX
1
.5
2
5
0 90 180
Phase Space Distribution
28
)(sin)(Im2)()2sin()(Re1)()( 22* rrrXXS
Shot Noise
Self-Squeezing of Light Nonlinear Optics: Complex Kerr Medium
Amplitude Phase
29
Tom Purdy JILA 30
Self-Squeezing of Light
kHz kHz
Sept. 9, 2013 Frontiers in Nanomechanics
31
Building Better Mechanical Resonators
asymmetric modes
are dipole-like. Radiate more, lower Q
The membrane acts as an acoustic radiatior. Energy is dissipated when the radiated waves encounter lossy boundary.
I. Wilson-Rae, et al., PRL (2011) P.-L. Yu, T. P. Purdy, and C. A. Regal, PRL (2012)
symmetric modes are quadrupole-like (or higher order).
Radiate less, higher Q
(3,3)
(1,3)
Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 32
Building Better Mechanical Resonators Eliminate acoustic radiation
Wilson-Rae, et al., PRL 106, 047205 (2011) Yu et al., PRL 108, 083603 (2012)
Acoustic radiation shield at GHz: J. Chan et al., APL (2012) Painter Group
Qext > 108
High
low
Mechanical D
isplacement (log scale)
Qext ~ 106
Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 33
Building Better Mechanical Resonators Driven
displacemen
t (m) Acoustic
Band Gap
Phononic Crystal Bare Substrate
Frequency (kHz)
Work in progress: Measuring band gaps
Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 34
Conclusions
• Optomechanics experiments in a strong measurement regime
1. Observe radiation pressure shot noise 2. Create squeezed light
• This resource is useful to: 1. Avoid measurement backaction using
squeezed light 2. Perform microwave ↔ optical state
transfer at the single quanta level
The Regal Optomechanics Lab: Bob Peterson Ben Yu Nir Kampel Alec Jenkins Cindy Regal Electromechanics Collaborators: JILA: Reed Andrews Konrad Lehnert NIST: Kat Cicak Ray Simmonds John Teufel
Acknowledgements
Research Funded by: NSF, DARPA, ONR
Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 35