Advanced Workshop on Nanomechanics September Quantum Measurement in an Optomechanical System

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1 Advanced Workshop on Nanomechanics 9-13 September 2013 Quantum Measurement in an Optomechanical System Tom Purdy JILA - NIST & University of Colorado U.S.A.

2 Tom Purdy, JILA NIST & University it of fcolorado with Bob Peterson, Ben Yu, Nir Kampel, Alec Jenkins, Cindy Regal Position Uncertainty Thermal Motion SQL Measurement Laser Power

3 Big Range of Optomechanical Systems Small LIGO 10 kg 10 km Macroscopic Systems Membrane Optomechanics 10 ng 1 mm Nanomechanics Single Atom in Optical Tweezers kg 10 nm m 4 km Ligo.caltech.edu Ligo.caltech.edu 1 m Sept. 9, 2013 Frontiers in Nanomechanics A. Kaufman, et al., PRX 2, (2012)

4 Big Range of Optomechanical Systems Small LIGO 10 kg 10 km Macroscopic Systems Membrane Optomechanics 10 ng 1 mm Nanomechanics Single Atom in Optical Tweezers kg 10 nm m 4 km Ligo.caltech.edu High precision interferometry Squeezed light Quantum Nondemolition Measurements Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA Raman Sideband Cooling Optical Tweezers Electromagnetically Induced Transparency 3

5 Membrane Cavity Optomechanical System Raman Sideband Cooling Introduction to quantum measurement Observing quantum measurement backaction Overview Using mechanical motion to measure light Building better mechanical resonators Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 4

6 Membrane Optomechanical System Si 3 N 4 dielectric membrane (1,1) 0.5 mm X 0.5 mm X 50 nm (2,2) High Tension ~ GPa High Mechanical Quality Factor (4,4) MHz mechanical resonance frequencies 10% reflectivity, low optical absorption Low mass ~10 ng Sept. 9, 2013 Frontiers in Nanomechanics Verbridge, et al., JAP 99, (2006) Southworth, et al., PRL 102, (2009) Unterreithmeier, et al., PRL 105, (2010) Wilson-Rae, et al., PRL 106, (2011) Yu et al., PRL 108, (2012) Thompson, et al., Nature (2008) Wilson et al., PRL (2009) Karuza, et al., NJP, 14, (2012) Purdy, et al., NJP, (2012)

7 Optomechanical Coupling Membrane Photodetector Input laser Optical Intensity Mirror Mirror Mechanical Displacement Spectrum Transmission Optical Frequency Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 6

8 Optomechanical Device Compact, low vibration, low drift design Cryogenically compatible (4K flow cryostat) Membrane Piezoelectric Actuator Mirror High optical finesse (<30,000) Low mechanical dissipation small 4 K Invar Spacer 1 Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 7

9 Laser Cooling Raman Sideband Cooling m C m n m m = Mechanical frequency = number of mechanical vibrational quanta = Cavity frequency = number of photons Sept. 9, 2013 Frontiers in Nanomechanics n m 0 Tom Purdy JILA Anti-Stokes n m 1 n m 2 n m 3 Monroe Wineland, PRL 75, 4011 (1995) Teufel, et al., Nature 475, 359 (2011) Chan, et al., Nature 478, 89 (2011) 8

10 Laser Cooling Raman Sideband Cooling m C Input Laser m Optical Frequency Sept. 9, 2013 Frontiers in Nanomechanics n m 0 Tom Purdy JILA Anti-Stokes n m 1 n m 2 n m 3 Monroe Wineland, PRL 75, 4011 (1995) Teufel, et al., Nature 475, 359 (2011) Chan, et al., Nature 478, 89 (2011) 9

11 Laser Cooling Frequency (MHz) Increasing Laser Power Total motion Thermal motion Purdy, et al., NJP, (2012) Jayich, et al., NJP 14, (2012) Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 10

12 Laser Cooling Frequency (MHz) Increasing Laser Power Purdy, et al., NJP, (2012) Jayich, et al., NJP 14, (2012) Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 11

13 Quantum Limits of Optical Detection Interferometric Gravitational Wave Detector: It s like trying to infer the position of the moon by measuring the ocean s tides, but times harder Laser Test mass ~kg Beamsplitter Test mass Displacement Spectral Density Noise [m/hz 1/2 ] Ligo.caltech.edu 2physics.com Photodetector Fundamental Sensitivity Limits: Optical Shot Noise Radiation Pressure Shot Noise Limits theoretically identified decades ago, Caves, PRL (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, (2010) Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 12

14 Quantum Limits of Optical Detection Heisenberg s Microscope Thought Experiment Camera Microscope electron photon x imp p ba / 2 W. Heisenberg, Physical Principles of the Quantum Theory (1930) Tom Purdy JILA 13

15 Quantum Limits of Optical Detection Heisenberg s Microscope Thought Experiment Camera Microscope electron photon x imp p ba / 2 Tom Purdy JILA 14

16 Quantum Limits of Optical Detection Position Uncertainty Shot Noise statistical fluctuations of the number of photons detected in a given time interval Standard Quantum Limit Standard Quantum Limit Measurement Laser Power imp ba S z S F Radiation Pressure Shot Noise Randomly varying optical force fluctuations due to shot noise Tom Purdy JILA 15

17 Quantum Measurement Experiment Setup Membrane PD Signal Beam PBS PBS PD Meter Beam Mirror Mirror 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 Optical Frequency Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 16

18 Radiation Pressure Shot Noise Displacement Spectrum as measured by meter beam Signal Beam ON Signal Beam OFF Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 17

19 Radiation Pressure Shot Noise Position Uncertainty Thermal Motion SQL Measurement Laser Power Sept. 9, 2013 Frontiers in Nanomechanics 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 Tom Purdy JILA 18

20 Approaching the Standard Quantum Limit Position Uncertainty As measured by the Signal Beam 10 1 Thermal Motion SQL 1 10 Signal Beam Optical Power (W) Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 19

21 Radiation Pressure Shot Noise (2,2) mode well coupled (4,4) mode poorly coupled 0 0 Signal Beam Power 20

22 Quantum Measurement of Light 100 Thermal Motion Recoil motion 10 1 Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 21

23 Quantum Noise Cancellation GF, F Amp PD Intensity Modulator PBS PBS PD Signal Beam Meter Beam 1. Membrane senses signal beam intensity fluctuations 2. Meter beam reads out membrane displacement 3. Active feedback cancels signal beam intensity fluctuations Wiseman and Milburn, PRA, 49:1350 (1994) Mancini and Wiseman, J. of Opt. B, 2:260 (2000) See also Haroche group Cavity QED work Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 22

24 Quantum Noise Cancellation Meter Beam (relative to shot noise) Signal Beam 1.51 Feedback OFF Feedback ON 1.52 GF, F Amp PD Intensity Modulator PBS PBS PD Signal Beam Meter Beam 23

25 Quantum Noise Cancellation R=0.7 R=1.3 R=2.6 RPSN to Thermal Force Ratio 3 R (Electronic Gain) Signal Beam Power (W) Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 24

26 Self-Squeezing of Light Transmission Optical Frequency Purdy, et al., PRX, in press (2013) arxiv: Safavi-Naeini, et al., Nature 500, 185 (2013) Brooks, et al., Nature 488, 476 (2012) a Tom Purdy JILA

27 Self-Squeezing of Light Transmission Quantum Efficiency Thermal Noise Optical Frequency Purdy, et al., PRX, in press (2013) arxiv: Safavi-Naeini, et al., Nature 500, 185 (2013) Brooks, et al., Nature 488, 476 (2012) b Tom Purdy JILA 26

28 Self-Squeezing of Light (relative to shot noise) (1,1) (1,2) (2,2) (1,3) (2,3) (2,4) (3,4) (1,5) (2,5)

29 X X out I out Q X X in I in Q Self-Squeezing of Light Nonlinear Optics: Complex Kerr Medium Self Phase ModulationSqueezed Light X S rx in I X I cos X X * ( ) X ( ) Q X amplitude quadratue I X Q phase quadrature sin 2 1 Rer ( ) sin(2 ) r( ) 2Imr ( ) 2 sin ( ) 5 Phase Space Distribution 2 Shot Noise

30 Self-Squeezing of Light Nonlinear Optics: Complex Kerr Medium Phase Amplitude 29

31 Self-Squeezing of Light khz khz Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 30

32 Building Better Mechanical Resonators The membrane acts as an acoustic radiatior. Energy is dissipated when the radiated waves encounter lossy boundary. asymmetric modes are dipole-like. Radiate more, lower Q (1,3) symmetric modes are quadrupole-like (or higher order). Radiate less, higher Q (3,3) I. Wilson-Rae, et al., PRL (2011) P.-L. Yu, T. P. Purdy, and C. A. Regal, PRL (2012) 31

33 Building Better Mechanical Resonators Eliminate acoustic radiation Wilson-Rae, et al., PRL 106, (2011) Yu et al., PRL 108, (2012) High Mechanical Displacement (log scale) Q ext ~ 10 6 Q ext > 10 8 low Acoustic radiation shield at GHz: J. Chan et al., APL (2012) Painter Group Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 32

34 Building Better Mechanical Resonators Work in progress: Measuring band gaps Acoustic Band Gap Driven displacement (m) Phononic Crystal Bare Substrate Frequency (khz) Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 33

35 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 Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 34

36 Acknowledgements 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 Research Funded by: NSF, DARPA, ONR Sept. 9, 2013 Frontiers in Nanomechanics Tom Purdy JILA 35