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Interferometer as a New F ield of a Quantum P hysics - the Macroscopic Quantum System -

Interferometer as a New F ield of a Quantum P hysics - the Macroscopic Quantum System - . Nobuyuki Matsumoto Tsubono lab University of Tokyo. Elites Thermal Noise Workshop @ University of Jena Aug 21, 2012.

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Interferometer as a New F ield of a Quantum P hysics - the Macroscopic Quantum System -

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  1. Interferometer as a New Field of a Quantum Physics- the Macroscopic Quantum System - Nobuyuki Matsumoto Tsubono lab University of Tokyo Elites Thermal Noise Workshop @ University of Jena Aug 21, 2012

  2. Tsubono Lab @ University of Tokyo • Directed by Prof. KimioTsubonoof department of physics at university of Tokyo • Research on Relativity, Gravitational Wave, and Laser Interferometer

  3. motivation • Interferometer can detect gravitational waves and study quantum physics because the quantum nature of the light can move to a state of the mirror via the radiation pressure of light →Macroscopicquantum physics can be studied!

  4. Abstract Goal Providing a new field to study quantum physics Ex. • Studying a quantum de-coherence • Generation of a macroscopic “cat state” • Generation of a squeezed light Requirement Observation of a Quantum Radiation Pressure Fluctuations (QRPF)

  5. Outline • Introduction • Effect of a radiation pressure force • Radiation Pressure Interferometer • Prior Research • Our Proposal • Summary

  6. I. Introduction • What is the light? Wave-particle duality ↓ Uncertainty principle ↓　　　　　　　　　　　　 ↓ Standard quantum limit quantum non-demolition (SQL) measurement (QND) →ultimate limit →surpassing the SQL ΔX1:fluctuations of the amplitude quadrature → induce a radiation pressure noise ΔX2:fluctuations of the phase quadrature → induce a shot noise ΔX1=ΔX2 (vacuum state) ΔX1 or ΔX2 <1 (squeezed state)

  7. I. Introduction • Quantum effect ina gravitational detector →quantum noise originated by the vacuum (ground state) fluctuations DC power + Vacuum Fluctuations (Quantum Sideband) common Laser Quantum Sideband PD differential

  8. I. Introduction • Generation of the squeezed light & Reduction of shot noise our squeezed vacuum generator via χ(2) effect ↑ Optical Parametric Oscillator (OPO) ↓ Down conversion (green → IR) ↑　　　　　　　 Nonlinear media (PPKTP) ↑ ↑ Seed (1064 nm) ↑ ↓ ↓ ↓ Pump, Green light (532 nm) ↓ Correlated IR light

  9. I. Introduction • Quantum effect in an opt-mechanical system →QRPF arenot noises but signals! Fixed mirror →opt-mechanical system ↓ ↓ ↓ ↓ Movable mirror → DC power →classical effect → power fluctuations →quantum effect induced by QRPF radiation pressure of light ↓ ↓ ↓ Mediation between the mechanical system and the optical system

  10. II. Effect of a radiation pressure force • Optical spring effect Fixed mirror Spring effect Movable mirror PHYSICAL REVIEW A 69, 051801(R) (2004)

  11. II. Effect of a radiation pressure force • Siddles-Sigg Instability (anti-spring effect) PHYSICAL REVIEW D 81, 064023 (2010)

  12. II. Summary of the review • Opt-mechanical effects • Classical effects • Spring effect • Instability • Cooling And so on・・・ • Quantum effects • Squeezing • Entanglement • QND And so on・・・ Measured Not measured No one see even QRPF

  13. III. Radiation Pressure Interferometer • Interferometer to study quantum physics using a radiation pressure effect • Difficulty • Weak force light test mass low stiffness high power beam • Siddles-Sigg instability high stiffness low power beam Technical trade-off SensitivityvsInstability configuration

  14. IV. Prior Research • Suspended tiny mirror (linear FP) • High susceptibility due to low stiffness • Do not have a much tolerance for restoring a high power beam • MEMS (Micro Electro Mechanical Systems) • Light (~100 ng) but not high susceptibility due to high stiffness • Have a much tolerance for restoring a high power beam

  15. IV. Prior Research • Suspended tiny mirror (linear FP) Flat mirror PHYSICAL REVIEW D 81, 064023 (2010) Φ30 mm C. R. Physique 12 (2011) 826–836 Width 1.5 mm Q ~ 7.5e5

  16. IV. Prior Research • MEMS width Mass ~ 100 ng Q ~ 10^6-10^7 PHYSICAL REVIEW A 81, 033849 (2010)

  17. IV. Prior Research • Suspended mirror vs membrane

  18. V. Our Proposal • Triangular cavity Siddels-Sigg instability of yaw motion is eliminated without increasing the stiffness • Silica aerogel mirror (low density ~ 0.1 g/cm^3) More sensitive test mass

  19. Linear FP cavity V. Our Proposal Triangular cavity Membrane(MEMS) SN~4 with 300 K (aerogel, m=0.23 mg Q=300) ↓ Next, in detail SN~10 with 300 K (P_circ~1 kW, m=2.3 mg, Q=1e4) Displacement fluctuations induced by QRPF [m/Hz^1/2] SN~10 with 300 K (P_circ~1 kW, m=23 mg, Q=1e5) Can not observe with 300 K (P_circ~100 mW, m=23 mg, Q=1e5) SN~2 with 1 K Frequency [Hz]

  20. Circulating power is 800 W

  21. V-I. Triangular Cavity - : align - : misalign • Triangular cavity Can use a flat mirror! Angular (yaw) stability Angular (pitch) instability mirror

  22. V-I. Triangular Cavity • Yaw stability Reverse of the coordinate axis common differential - : align - : misalign Demonstration of the stability. a → movable b,c→ fixed ↓ Equations of motion Stability condition

  23. V-I. Triangular Cavity • Pitch instability Similar to the linear FP No reverse of the coordinate axis a → movable b,c→ fixed ↓ ～4e-7 N m (23 mg mirror) ↑ Equations of motion ↓ ～4e-7 N m (100 W, R=1 m, L=10 cm) Stability condition

  24. V-II. Demonstration Tungsten Φ20 um L=2 cm Κ=1.25e-7 N m Resonance frequency is 365 mHz Flat Φ12.7 mm h=6.35 mm M=1.77 g I=2.41e-8 kg m^2 Round trip length ～ 10 cm Finesse ～250 Power gain ～100 Round trip loss ～ 0.007 Mode match ～0.8 Input power ～ 1 W

  25. Sound-proofing Suspended mirror Photo-detector

  26. Piezo mounted mirror CylindricalOxygen-Free Copper Φ2×3 Eddy current dumping Doughnut-shapedNeodymium magnet Φ8×Φ4×5

  27. V-III. Aerogel Mirror • What is the aerogel? →materials in which the typical structure of the pores and the network is largely maintainedwhile the pore liquid of a gel is replaced by air The samples were prepared at university of Kyoto. (Inorganic Chemistry of Materials Laboratory)

  28. V-III. Aerogel Mirror • How to makethe aerogel? Supercritical drying technique ↑phase diagram Natural drying ↑Meniscus

  29. V-III. Aerogel Mirror • Physical property

  30. V-III. Aerogel Mirror • Structure • Colloidal gel • Polymeric gel

  31. V-III. Aerogel Mirror • Mechanical quality factor of silica aerogel

  32. V-III. Aerogel Mirror • How to make a good mirror? (finesse > 1000) • Polishing hydrophilic aerogel → freon or dry nitrogen gas (`slurry’ gas, it is impossible to use water) & diamond lapping film (~0.3 um roughness)(fixedabrasive machining technique) hydrophobicaerogel → OSCAR polishing (slurry) (freeabrasive machining technique) • Coating Dielectric multilayer will be prepared by ion beam sputtering

  33. V-III. Aerogel Mirror 10-11 Qfactor 2000 Qfactor 300 10-12 10-13 10-14 Physical property of aerogel ⇒ density 100 kg/m3, Young’s modulus 30 MPa,Qfactor300

  34. VI. Summary • Opt-mechanical system →interesting system to study quantum physics • Triangular cavity →decrease the stiffness without being induced instability • Aerogel mirror →more sensitive mirror

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