MAQRO Testing Quantum Physics in Space

Transcription

1 MAQRO Testing Quantum Physics in Space 1 Rainer Kaltenbaek, 2 Gerald Hechenblaikner, 1 Nikolai Kiesel, 2 Ulrich Johann, 1 Markus Aspelmeyer 1 Vienna Center for Quantum Science and Technology Faculty of Physics, University of Vienna, Austria 2 EADS Astrium Friedrichshafen Immenstaad, Germany Collaborators: Oriol Romero-Isart (MPI Munich) Keith C. Schwab (Caltech)

2 Q2C5 - Köln Slide 2 of 24 What is MAQRO? Macroscopic Quantum ResOnators Fundamental, medium-sized space mission R. Kaltenbaek et al., Exp. Astronomy 34, 123 (2012) Central experiment: DECIDE (Decoherence in a double-slit experiment)

3 Q2C5 - Köln Slide 3 of 24 What is MAQRO? Macroscopic Quantum ResOnators Fundamental, medium-sized space mission R. Kaltenbaek et al., Exp. Astronomy 34, 123 (2012) Central experiment: DECIDE (Decoherence in a double-slit experiment) Is there a transition between quantum and classical?

4 Q2C5 - Köln Slide 4 of 24 What is MAQRO? Macroscopic Quantum ResOnators Fundamental, medium-sized space mission R. Kaltenbaek et al., Exp. Astronomy 34, 123 (2012) Central experiment: DECIDE (Decoherence in a double-slit experiment) Is there a transition between quantum and classical? If so, where does it begin?

5 Q2C5 - Köln Slide 5 of 24 What is MAQRO? Macroscopic Quantum ResOnators Fundamental, medium-sized space mission R. Kaltenbaek et al., Exp. Astronomy 34, 123 (2012) Central experiment: DECIDE (Decoherence in a double-slit experiment) Is there a transition between quantum and classical? If so, where does it begin? Superpositions of arbitrarily large & massive objects?

6 Q2C5 - Köln Slide 6 of 24 What is MAQRO? Macroscopic Quantum ResOnators Fundamental, medium-sized space mission R. Kaltenbaek et al., Exp. Astronomy 34, 123 (2012) Central experiment: DECIDE (Decoherence in a double-slit experiment) Is there a transition between quantum and classical? If so, where does it begin? Superpositions of arbitrarily large & massive objects? See also Markus Arndt s talk

7 Q2C5 - Köln Slide 7 of 24 Superposition & Interference Classical Mechanics: Interference is a wave phenomenon Quantum Mechanics: Interference also for particles Indistinguishable processes probability amplitudes interfere

8 Q2C5 - Köln Slide 8 of 24 But what is really happening? From J. D. Norton, Universtiy of Pittsburgh Interference for every single particle Not a statistical phenomenon By Paul Ehrenfest A. Tonomura et al., Amer. J. Phys. 57, 117 (1989), Hitachi

9 Q2C5 - Köln Slide 9 of 24 But what is really happening? From J. D. Norton, Universtiy of Pittsburgh Interference for every single particle Not a statistical phenomenon Particles do not pass either through one or the other slit By Paul Ehrenfest A. Tonomura et al., Amer. J. Phys. 57, 117 (1989), Hitachi

10 Q2C5 - Köln Slide 10 of 24 But what is really happening? From J. D. Norton, Universtiy of Pittsburgh By Paul Ehrenfest Interference for every single particle Not a statistical phenomenon Particles do not pass either through one or the other slit The path of a particle is not real. A. Tonomura et al., Amer. J. Phys. 57, 117 (1989), Hitachi

11 Q2C5 - Köln Slide 11 of 24 Where does classical reality begin? The Quantum Measurement Problem Schrödinger s Cat Atom in a superposition of decayed and not decayed cat in a superposition of dead and alive?

12 Q2C5 - Köln Slide 12 of 24 Where does classical reality begin? The Quantum Measurement Problem Schrödinger s Cat Atom in a superposition of decayed and not decayed cat in a superposition of dead and alive? Does Quantum Mechanics fail for large/massive systems?

13 Q2C5 - Köln Slide 13 of 24 Where does classical reality begin? The Quantum Measurement Problem Schrödinger s Cat Atom in a superposition of decayed and not decayed cat in a superposition of dead and alive? Does Quantum Mechanics fail for large/massive systems? When do things become real?

14 Q2C5 - Köln Slide 14 of 24 Macrorealism Inherent transition from quantum to classical NO Schrödinger Cats Modification of Schrödinger equation -> decoherence Physical reasons for the collapse : F. Károlyházy, Nuovo Cimento A 52, 390 (1966) L. Diosí, PRA 105, 199 (1984) R. Penrose, e.g., Gen. Rel. Grav. 28, 581 (1996) Ghirardi, Rimini & Weber, PRD 34, 470 (1986) Continuous sponataneous localization, Ghirardi, Pearle & Rimini, PRA 42, 78 (1990) Heisenberg uncertainty uncertainty in metric randomizes phase for macroscopic superpositions

15 Q2C5 - Köln Slide 15 of 24 Macrorealism Inherent transition from quantum to classical NO Schrödinger Cats Modification of Schrödinger equation -> decoherence Physical reasons for the collapse : F. Károlyházy, Nuovo Cimento A 52, 390 (1966) L. Diosí, PRA 105, 199 (1984) R. Penrose, e.g., Gen. Rel. Grav. 28, 581 (1996) Ghirardi, Rimini & Weber, PRD 34, 470 (1986) Continuous sponataneous localization, Ghirardi, Pearle & Rimini, PRA 42, 78 (1990) non-relativistic extension of QM to include Newtonian gravitation soliton-like localized solutions

16 Q2C5 - Köln Slide 16 of 24 Macrorealism Inherent transition from quantum to classical NO Schrödinger Cats Modification of Schrödinger equation -> decoherence Physical reasons for the collapse : F. Károlyházy, Nuovo Cimento A 52, 390 (1966) L. Diosí, PRA 105, 199 (1984) R. Penrose, e.g., Gen. Rel. Grav. 28, 581 (1996) Ghirardi, Rimini & Weber, PRD 34, 470 (1986) Continuous sponataneous localization, Ghirardi, Pearle & Rimini, PRA 42, 78 (1990) macroscopic superpositions superposition of spacetimes unstable superposition collapses

17 Q2C5 - Köln Slide 17 of 24 Macrorealism Inherent transition from quantum to classical NO Schrödinger Cats Modification of Schrödinger equation -> decoherence Physical reasons for the collapse : F. Károlyházy, Nuovo Cimento A 52, 390 (1966) L. Diosí, PRA 105, 199 (1984) R. Penrose, e.g., Gen. Rel. Grav. 28, 581 (1996) Ghirardi, Rimini & Weber, PRD 34, 470 (1986) Continuous sponataneous localization, Ghirardi, Pearle & Rimini, PRA 42, 78 (1990) macroscopic each constituent superpositions particle spontaneously superposition collapses of spacetimes with rate unstable λ superposition collapses single collapse of constituent reduces DM of composite system

18 Q2C5 - Köln Slide 18 of 24 Do massive objects interfere? Matter-wave interferometry L. Hackermüller et al., Nature 427, 711 (2004) Quantum Optomechanics G. D. Cole et al., Appl. Phys. Lett. 92, (2008)

19 Q2C5 - Köln Slide 19 of 24 Do massive objects interfere? Matter-wave interferometry L. Hackermüller et al., Nature 427, 711 (2004) Quantum Optomechanics Advantage: address & cool single system G. D. Cole et al., Appl. Phys. Lett. 92, (2008)

20 Q2C5 - Köln Slide 20 of 24 Do massive objects interfere? Matter-wave interferometry L. Hackermüller et al., Nature 427, 711 (2004) Quantum Optomechanics Advantage: address & cool single system Disadvantage: coupling to environment via support G. D. Cole et al., Appl. Phys. Lett. 92, (2008)

21 Q2C5 - Köln Slide 21 of 24 Optically trapped nanospheres Use levitated dielectric spheres no mechanical support high mechanical Q Combine established technology (A. Ashkin, PRL 24, 147 (1970)) with optomechanics use atom-trapping toolbox D. E. Chang et al., PNAS 107, 1005 (2010) O. Romero-Isart et al., New J. Phys. 12, (2010) O. Romero-Isart et al., PRA 83, (2011)

22 General approach Have to estimate predictions from Macrorealistic Models Have to take into account all relevant Decoherence Mechanisms to get the prediction from quantum theory WHY? Regime where QM still allows for coherent phenomena but macrorealistic models do not? Experimentally test for interference How can we see interference? Double-slit experiment cool expand prepare expand & measure See O. Romero-Isart et al., PRL 107, (2011); R. Kaltenbaek et al., Exp. Astronomy 34, 123 (2012) Q2C5 - Köln Slide 22 of 24

23 Q2C5 - Köln Slide 23 of 24 Preparing the double slit slide 1 Local decoherence via a short, tightly focused UV pulse 1. Start well localized

24 Q2C5 - Köln Slide 24 of 24 Preparing the double slit slide 1 Local decoherence via a short, tightly focused UV pulse 1. Start well localized 2. Free expansion

25 Q2C5 - Köln Slide 25 of 24 Preparing the double slit slide 1 Local decoherence via a short, tightly focused UV pulse 1. Start well localized 2. Free expansion 3. Apply UV pulse

26 Q2C5 - Köln Slide 26 of 24 Preparing the double slit slide 1 Local decoherence via a short, tightly focused UV pulse 1. Start well localized 2. Free expansion 3. Apply UV pulse Incoherent mixture of two states

27 Q2C5 - Köln Slide 27 of 24 Preparing the double slit slide 1 Local decoherence via a short, tightly focused UV pulse 1. Start well localized 2. Free expansion 3. Apply UV pulse Localized Incoherent mixture of two states Superposition

28 Q2C5 - Köln Slide 28 of 24 Preparing the double slit slide 2 1D density matrix representation

29 Q2C5 - Köln Slide 29 of 24 Approximation via cat state Rough approximation for simple estimates of: Free-fall times Comparison of interference visibilities Interference-fringe spacing

30 Q2C5 - Köln Slide 30 of 24 Approximation via cat state Rough approximation for simple estimates of: Free-fall times Comparison of interference visibilities Interference-fringe spacing Fit gaussian to coherent part

31 Q2C5 - Köln Slide 31 of 24 Approximation via cat state Rough approximation for simple estimates of: Free-fall times Comparison of interference visibilities Interference-fringe spacing Fit gaussian to coherent part Use superposition of Gaussians: Where the Gaussian states are:

32 Q2C5 - Köln Slide 32 of 24 Decoherence Overall framework for Quantum Theory & Macrorealism Long-wavelength limit: M. R. Gallis & G. N. Fleming, PRA 42, 38 (1990) & G. N. Fleming, Found. Phys. 20, 159 (1990) According to Quantum Theory: Gas collisions Scattering of black-body radiation Emission of black-body radiation Absorption of black-body radiation O. Romero-Isart et al., PRL 107, (2011) R. Kaltenbaek et al., Exp. Astronomy 34, 123 (2012) O. Romero-Isart, PRA 84, (2011)

33 Q2C5 - Köln Slide 33 of 24 Decoherence Overall framework for Quantum Theory & Macrorealism Long-wavelength limit: M. R. Gallis & G. N. Fleming, PRA 42, 38 (1990) & G. N. Fleming, Found. Phys. 20, 159 (1990) According to Quantum Theory: Gas collisions Very good vacuum (< Pa) Scattering of black-body radiation Emission of black-body radiation Absorption of black-body radiation O. Romero-Isart et al., PRL 107, (2011) R. Kaltenbaek et al., Exp. Astronomy 34, 123 (2012) O. Romero-Isart, PRA 84, (2011)

34 Q2C5 - Köln Slide 34 of 24 DECIDE DECoherence In a Double-slit Experiment MAQRO, space proposal, R. Kaltenbaek, G. Hechenblaikner, N. Kiesel, U. Johann & M. Aspelmeyer (2010) published as: Macroscopic Quantum Resonators (MAQRO), R. Kaltenbaek, G. Hechenblaikner, N. Kiesel, O. Romero- Isart, K. C. Schwab, U. Johann, & M. Aspelmeyer, Exp. Astronomy 34, 123 (2012)

35 Q2C5 - Köln Slide 35 of 24 DECIDE DECoherence In a Double-slit Experiment radiating and venting to space MAQRO, space proposal, R. Kaltenbaek, G. Hechenblaikner, N. Kiesel, U. Johann & M. Aspelmeyer (2010) published as: Macroscopic Quantum Resonators (MAQRO), R. Kaltenbaek, G. Hechenblaikner, N. Kiesel, O. Romero- Isart, K. C. Schwab, U. Johann, & M. Aspelmeyer, Exp. Astronomy 34, 123 (2012)

36 Q2C5 - Köln Slide 36 of 24 Advantages of thermal shield Low temperature (30-40 K, trying to improve it further) Ultra-high vacuum (< Pa) No vibrations Low weight No limit to life-time due to limited amount of Helium etc. Stable mass distribution

37 Q2C5 - Köln Slide 37 of 24 Quantum vs. Macrorealism What could we do with state of the art parameters? i.e.: 32 K environment, fused-silica nanosphere, UV wavelength of 350 nm with typical fused-silica parameters: T i =98K Blue: r=5nm, Dark gray: r=10nm, Orange: r=15nm Solid: quantum theory Dashed: CSL model (continuous spontaneous localization

38 Q2C5 - Köln Slide 38 of 24 Quantum vs. Macrorealism What could we do with state of the art parameters? i.e.: 32 K environment, fused-silica nanosphere, UV wavelength of 350 nm with typical fused-silica parameters: T i =98K Need lower-absorption material Blue: r=5nm, Dark gray: r=10nm, Orange: r=15nm Solid: quantum theory Dashed: CSL model (continuous spontaneous localization

39 Q2C5 - Köln Slide 39 of 24 Quantum vs. Macrorealism What could we do with state of the art parameters? i.e.: 32 K environment, fused-silica nanosphere, UV wavelength of 350 nm with typical fused-silica parameters: T i =98K Need lower-absorption material Blue: r=5nm, Dark gray: r=10nm, Orange: r=15nm Solid: quantum theory Dashed: CSL model (continuous spontaneous localization To test more than CSL: even more improvements

40 Q2C5 - Köln Slide 40 of 24 Improvements to be made Even lower absorption (better knowledge of optical properties of nanosphere material) Lower environment temperature Larger particles Higher mass density Lower thruster noise Shorter UV wavelength and/or sharper beam edges

41 Q2C5 - Köln Slide 41 of 24 Reducing the UV wavelength Much shorter UV wavelength: 35 nm Blue: r=10nm, Dark gray: r=15nm, Orange: r=20nm Blue: r=5nm, Dark gray: r=10nm, Orange: r=15nm Solid: quantum theory Dashed: CSL model (continuous spontaneous localization) Blue: r=20nm, Dark gray: r=35nm, Orange: r=50nm

42 Q2C5 - Köln Slide 42 of 24 Reducing the UV wavelength Much shorter UV wavelength: 35 nm Blue: r=10nm, Dark gray: r=15nm, Orange: r=20nm Blue: r=5nm, Dark gray: r=10nm, Orange: r=15nm Solid: quantum theory Dashed: CSL model (continuous spontaneous localization) Relaxes the need for lower-absorption material Blue: r=20nm, Dark gray: r=35nm, Orange: r=50nm

43 Reducing the UV wavelength Much shorter UV wavelength: 35 nm Blue: r=10nm, Dark gray: r=15nm, Orange: r=20nm Blue: r=5nm, Dark gray: r=10nm, Orange: r=15nm Solid: quantum theory Dashed: CSL model (continuous spontaneous localization) Relaxes the need for lower-absorption material Still not more than CSL Blue: r=20nm, Dark gray: r=35nm, Orange: r=50nm Q2C5 - Köln Slide 43 of 24

44 Q2C5 - Köln Slide 44 of 24 Lower temperature Lower environment temperature: 16 K Greater particle radii Different mass densities ρ = 2201 kg/m 3 Blue: r=80nm, Dark gray: r=90nm, Orange: r=100nm Solid: quantum theory Dashed: Károlyházy model

45 Q2C5 - Köln Slide 45 of 24 Lower temperature Lower environment temperature: 16 K Greater particle radii Different mass densities ρ = 4000 kg/m 3 Blue: r=80nm, Dark gray: r=90nm, Orange: r=100nm Solid: quantum theory Dashed: Károlyházy model

46 Q2C5 - Köln Slide 46 of 24 Lower temperature Lower environment temperature: 16 K Greater particle radii Different mass densities ρ = 5000 kg/m 3 Blue: r=80nm, Dark gray: r=90nm, Orange: r=100nm Solid: quantum theory Dashed: Károlyházy model

47 Q2C5 - Köln Slide 47 of 24 Lower temperature Lower environment temperature: 16 K Greater particle radii Different mass densities ρ = 9680 kg/m 3 Blue: r=80nm, Dark gray: r=90nm, Orange: r=100nm Solid: quantum theory Dashed: Károlyházy model

48 Q2C5 - Köln Slide 48 of 24 Free-fall times For state-of-the-art parameters (with Ti=40K) For future parameters (T=16K, Ti=25K, ) quantum theory vs. the CSL model quantum theory vs. the K model For r=10nm and ρ = 2201 kg/m 3 For r=70nm and ρ = 9680 kg/m 3

49 Q2C5 - Köln Slide 49 of 24 Free-fall times For state-of-the-art parameters (with Ti=40K) For future parameters (T=16K, Ti=25K, ) quantum theory vs. the CSL model quantum theory vs. the K model For r=10nm and ρ = 2201 kg/m 3 For r=70nm and ρ = 9680 kg/m 3 Even hard in space

50 Q2C5 - Köln Slide 50 of 24 Free-fall times For state-of-the-art parameters (with Ti=40K) For future parameters (T=16K, Ti=25K, ) quantum theory vs. the CSL model quantum theory vs. the K model For r=10nm and ρ = 2201 kg/m 3 For r=70nm and ρ = 9680 kg/m 3 Even hard in space Need to reduce free-fall time

51 Q2C5 - Köln Slide 51 of 24 Thruster noise Need Microthrusters (atmospheric drag, solar radiation pressure, ) But: finite force noise Random walk of spacecraft velocity Increasing position uncertainty between spacecraft & nanosphere Equivalent decoh. Parameter LISA requirements DECIDE requirements

52 Q2C5 - Köln Slide 52 of 24 Things to be done Find accurate optical properties for all particle materials Full simulation of interference pattern Optimize thermal shield Reduce internal temperature of particles Lower laser wavelength (better materials) Tailor thermal radiation to achieve lower equilibrium temperature Better cavity to allow for lower trap intensity Realize side-band cooling in the lab Implement nanoparticle loading mechanism Demonstrate preparation of double-slit in the lab Can we find a way to use longer UV wavelengths? Find way to reduce free-fall times (shorter UV wavelength, different UV beam shape, gravity gradient, )

53 Q2C5 - Köln Slide 53 of 24 Thanks I/II Thanks for discussions: Thanks for info on LTP and for graphics: Sebastian Hofer Johannes Burkhard (Astrium) Klemens Hammerer Jens Burkhard (Astrium) Garrett Cole Tobias Ziegler (Astrium) Nico Brandt (Astrium) Thanks for funding:

54 Q2C5 - Köln Slide 54 of 24 Thanks II/II THANK YOU Collaborations are welcome