New avenues for the coherent manipulation of clusters and molecules

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1 New avenues for the coherent manipulation of clusters and molecules Markus Arndt, Quantum Nanophysics Group (QNP) Vienna Center for Quantum Science & Technology (VCQ) University of Vienna

2 Happy Birthday, Philippe! Our joint interests

3 Why does quantum physics still surprise us? Everyday world Objects always in defined states Quantum world Quantum superpositions Subjective chance Objective randomness All interactions are local Information is non local Reality Potentiality? Look for: Macroscopic Quantum Superpositions and Quantum Entanglement

4 Matter waves physics the heart of quantum physics Louis de Broglie Erwin Schrödinger Davisson/Germer & Thomson db h m v Formal equation Experimental verification

Time line of matter wave interferometry Many atoms: 10 3 10 9 Ultra cold: 1 pk.

C 60 /C 70 (1999) Electron (1927) Neutron (1936) He Atoms &H 2 (1930) Atoms &

5 Time line of matter wave interferometry Many atoms: Ultra cold: 1 pk.. 1 µk Atom binding: weak λ db : single atoms Atomic BEC (1995)? C 60 /C 70 (1999) Electron (1927) Neutron (1936) He Atoms &H 2 (1930) Atoms & dimers He 2, Na 2, I 2 (80 s 90 s) Many atoms: Hot!: 4 K K Binding: ev λ db : entire complex

6 So far: Schrödinger's wave equation holds all tests This equation underlies all practical implementations of modern quantum information concepts. But: It is not written in stone May there be modifications at high mass or complexity? Erwin Schrödinger s grave in Alpbach

Tools of Molecular Quantum Nanophysics GROUP:

Mass & Complexity In Quantum Interference An

2011 Rev. Mod. Phys. 2012 Haslinger et al.

7 Tools of Molecular Quantum Nanophysics GROUP: Markus Arndt Far-Field Intererometry Highest Mass & Complexity In Quantum Interference An Ionizing Interferometer in the Time Domain Coming up Juffmann et al. Nature Nano. (2012) Gerlich et al. Nature Communs Rev. Mod. Phys Haslinger et al NEW NEW > 800 atoms/molecules > amu > 25% interference

8 C 60 Sourc e Veloc Selec tor ity 1.13 m G ratin g 5 µm 5µm Col limati on 1.3 3m L aser Ioniz ation The smoking gun of wave phenomena: Interference Maximum on Maximum Amplification Maximum on Trough Cancellation

9 Far-field diffration with single molecules Evaporation: 445 nm, 100 mw Detection: 661 nm, 50 mw, EMCCD Grating: d=100 nm, s=50nm

10 Nanofabricated gratings

11 Single molecule fluorescence: molecule localization with 10 nm accuracy Evaporation: 445 nm, 100 mw Detection: 661 nm, 50 mw, EMCCD Abrupt bleaching from one frame to the next indicates single molecules

$Single molecule diffraction Juffmann et al.$

12 Single molecule diffraction Juffmann et al. Nature Nanotechnology DOI: /NNANO

13 Phthalocyanine Derivatives De Broglie: 2..5 pm Position (μm) PcH 2 : C 32 H 18 N 8 N=58, m=514 Position (μm) F 24 PcH 2 : C 48 H 26 F 24 N 8 O 8 N=114, m=1299

14 Near-field interference of macromolecules Kapitza-Dirac-Talbot-Lau Interferometry

15 Talbot Lau Effect: Coherent imaging with spatially incoherent radiation X-pos. ( units of d) Symmetric separation and in units of

Talbot-Lau interferometry db ~ 5 10-12 m, T

16 Talbot-Lau interferometry db ~ m, T ~ 1000 K Phys. Rev. Lett. 88, (2002).

17 Proving Quantum Delocalization & van der Waals forces in Talbot Lau interferometry Quantum + van der Waals Quantum without grating potential Quantum + Casimir Polder Phys. Rev. Lett. 88, (2002). Rev. Mod Phys. 84, (2012)

$Diffraction 3 rd Grating Detection Mask EI QMS 1 st Grating Coherence Nature Physics 3, 711$

18 Circumventing van der Waals forces: Kapitza-Dirac-Talbot-Lau Interferometer 2 nd Grating Diffraction 3 rd Grating Detection Mask EI QMS 1 st Grating Coherence Nature Physics 3, 711 (2007)

$Kapitza Dirac Talbot Lau interferometry 1 st Grating Coherence 2 nd Grating Diffraction 3 rd Grating Detection Mask Thermal Source$

19 Kapitza Dirac Talbot Lau interferometry 1 st Grating Coherence 2 nd Grating Diffraction 3 rd Grating Detection Mask Thermal Source Electron Impact Quadrupole Mass spectrometer / Nature Physics 3, 711 (2007) The laser field couples to the molecular polarizability :

20 Optical phase grating for molecules: dipole force between E field and polarizability dx ( yz, ) U( ) d E( x) 2 v

21 Precision requirements Gratings by Tim Savas, Massachusetts Institute of Technology & nm 2 Support structure: 1.5µm Photo lithographical manufacturing Period: nm Required accuracy : g < 0.5 Å < H atom!!

22 Molecules are no static points What is the role of the internal states?

23 Optical polarizability & optical absorption cross section influence the quantum interference visibility Classical prediction Quantum prediction New J. Phys. 11, (2009)

24 Quantum deflectometry measures Static polarizability / susceptibility Electric field Detector Power Supply [kv] Fringe shift x Phys. Rev A. 76, (2007).

25 Distinguishing structural isomers Identical chemical sum formula: C 49 H 16 F 52 Chem Comm 46, 4145 (2010) Identical mass: 1592 amu but different structure and different electric properties The molecules couple to a conservative potential, without leaving any position information behind!

Seeing thermally activated conformation oscillations Azobenzene derivative: No static dipole moment Many different conformations Surprise 1:

26 Seeing thermally activated conformation oscillations Azobenzene derivative: No static dipole moment Many different conformations Surprise 1: High contrast de Broglie interference Surprise 2: Dynamic dipole moments µ measurable Phys. Rev. A 81, (R) (2010) Dipole moment / Debye

27 Quantum Superposition of Molecular Octpusses Nature Communications 2, 263 (2011). m=5672 amu, N=356 atoms m=5310 amu, N=430 atoms

28 Provingthe quantumnatureof the interference pattern Classical model Quantum model TPPF84: 2814 amu, 202 atoms PFNS8: 5672 amu, 356 atoms

29 Does a Quantum Octopus qualify as a Schrödinger cat? The YES Argument A Schrödinger cat is an illustration for something that is complex, warm and macroscopic is simultaneoulsy in two unambiguously discernible states contains at least one biomolecule Image: Wikipedia

30 Does a Quantum Octopus qualify as a Schrödinger cat? The Quantum Octopus: > 400 atoms hotter than any cat (500 K) in a superposition of two position states: separated > 100 x size of the molecule

(classical) + microscopic (quantum) object Octopus : Does not need

31 Does a Quantum Octopus qualify as a Schrödinger cat? The NO and yet YES Argument Schrödinger cat: Entanglement between macroscopic (classical) + microscopic (quantum) object Octopus : Does not need entanglement to get in a quantum superposition Does get entangled in collisional decoherence unobserved Bell state

32 Practical and fundamental limits of quantum interference

33 What limits the observation of quantum interference? 1. Kinematics 2. Decoherence 3. Dephasing 4. Speculations about modifications of quantum mechanics

34 Kinematics: A car is just to massive g diff v=300 km/h m=1000 kg g = 2 m diff = db /g = 4 x rad This requires an experiment 30 trillion times the size of the visible universe!

35 Kinematic requirements for intereferometry in the mass range of m amu Target parameter Temperature : T 10 K, internal and external Velocity : v 1 m/s De Broglie wavelength : pm Vacuum : p 10 mbar Far field diffraction: Proposal: Found. Phys. DOI: /s Collimation to 2 µrad Nanograting with g=100 nm Expected diffraction pattern separated by 10 µm in 1 m distance Fluorescence detection Cluster Interferometry: Proposal: New J. Phys. 13, (2011) 3 VUV light gratings with g=79 nm Photoionization and TOF MS detection

36 What limits the observation of quantum interference? 1. Kinematics 2. Decoherence 3. Dephasing 4. Speculations about modifications of quantum mechanics

Decoherence The Idea Quantum system coupled to complex environment: generates entanglement Spreading of quantum coherence into the environment Ignorance of details in the environment

37 Decoherence The Idea Quantum system coupled to complex environment: generates entanglement Spreading of quantum coherence into the environment Ignorance of details in the environment leadstolossofcoherencein the Q System Early papers and easy readers about decoherence Zeh, H. Found. Phys. 3, 109 (1973). Caldeira, A. O. & A. J. Leggett, Physica A 121, 587 (1983) Joos, E., and H. D. Zeh, Z. Phys. B 59, 223 (1985) Zurek, W. H., Phys. Today, 1991, 44, 36 M. Schlosshauer, Decoherence and the Quantum to Classical Transition, Springer A. J. Leggett, Testing the Limits of Quantum Mechanics: Motivation, State of Play, Prospects, J. Phys.: Condens. Matter, 2002, 14, R415 R451 R. Omnès, Decoherence, Irreversibility, and Selection by Decoherence of Exclusive Quantum States with Definite Probabilities Phys. Rev. A, 2002, 65, 52119

38 Decoherence experiments ENS Paris: Decoherence of photonic cat states Brune. Haroche : Phys. Rev. Lett. 77, 4887 (1996). MIT, Cambridge: Decoherence in atom interferometry through photon scattering Chapman Prichtard : Phys. Rev. Lett. 75, 3783 (1995). Weizman Institute, Rehovot: Decoherence in electron interferometry in mesoscopic solids Sprinzak Heiblum: Phys. Rev. Lett. 84, 5820 (2000). NIST Boulder Decoherence of motional quantum states of trapped ions Turchette Wineland : Phys. Rev. A 62, (2000). Univ. Vienna: Collisional decoherence in fullerene interferometry Hornberger et al. Phys. Rev. Lett. 90, (2003). Decoherence of molecular matter waves by thermal emission of radiation Hackermüller et al. Nature 427, 711 (2004). Meanwhile Hundreds of papers related to Quantum information & Decoherence

39 The concept of decoherence: Ignorance of the environment loss of coherence in the Q System Assume: a quantum system in a superposition of a discrete set of states (Energies in atoms, Positions in a multi path interferometer ) Let the quantum system be coupled to a meter (in many cases the,meter is the unobserved environment) The meter measures quantum states: will create a (quantum) correlation The corresponding density matrix is obtained by taking the dyadic product of the state Before the measurement After the measurement

40 The concept of decoherence (continued ) If the quantum state of the meter (the environment) is not accounted for Trace over the meter (enviroment) states If (!) the meter states are orthonormal (i.e. unambiguously distinct):

41 The concept of decoherence (continued ) Reduced state has lost all coherences iff environmental states = orthogonal No fringe visibility, no interference All meter states are orthogonal (Decoherence Theory: Zeh, Leggett, Zurek ) Unambiguos which-path ( which-state ) information is available (Complementarity Principle, Bohr)

42 Collisions with Collisions background molecules Thermal photons Mean microcanonical Temperature (K) 1,0 1, Normalised Visibility 0,8 0,6 0,4 0, Pressure (in 10-7 mbar) Normalised Visibility 0,8 0,6 0,4 0,2 0, Incident Laser Power (W) Phys. Rev. Lett. 90, (2003). NATURE, 427, (2004).

43 What limits the observation of quantum interference? 1. Kinematics 2. Decoherence 3. Dephasing 4. Speculations about modifications of quantum mechanics

44 Grating vibrations : a trivial but important cause of not seeing quantum interference G 1 G 2 G 3 Common accelerations of all gratings Rotation of the interferometer Independent oscillations of all gratings

45 The presence of the Earth! Constant acceleration of the interferometer: Shift of the interference fringe x Shifts are velocity dependent x(v): Phase averaging and reduction of interference contrast Earth s rotation Earth s gravity sin 2 2 z G v L g x L v L x z Laser Phys. 15, (2004) exp z v c d v L V V sin 2 exp z v G d v L g V V

46 What limits the observation of quantum interference? 1. Kinematics 2. Decoherence 3. Dephasing 4. Speculations about modifications of quantum mechanics

47 Recent discussions in the literature To confront the value of λ in continuous spontaneous localization models, CSL, one would have to diffract molecules a factor of 10 6 larger (conventional CSL) factor of 10 2 larger ( new CSL) than the fullerenes.

48 Towards tests of continuous spontaneous localization in cluster interferometry Assuming a localization length of a = 100 nm Phys. Rev. A 83, (2011).

49 Long observation times Microgravity in space Talbot-length: / Smallest laser grating period : 78.5 nm (limited by existing lasers and ) Assume high mass and T=10 K 2 amu v= 0.4 m/s 1 pm amu v = 2.5 mm/s 15 fm Existing Vienna OTIMA interferometer can cope with 200 fm. Can easily be stretched by 10x to apparatus size of L=0.5 m But time of flight : 30 ms for 10 6 amu OK on earth 3 sec for 10 8 amu still OK in drop tower or parabolic flight 300 s for amu would work in microgravity

Summary and Outlook GROUP: Markus Arndt New methods for

Quantum Interference An Ionizing Interferometer in the Time

Nature Communs. 2011 Tüxen et al. in preparation (2012) Rev.

50 Summary and Outlook GROUP: Markus Arndt New methods for Far-Field Intererometry Highest Mass & Complexity In Quantum Interference An Ionizing Interferometer in the Time Domain Juffmann et al. Nature Nano (2012) Gerlich et al. Nature Communs Tüxen et al. in preparation (2012) Rev. Mod. Phys Haslinger et al. (2012) NEW NEWs coming up NEWS coming up

$array Diffraction Screen$ High mass High internal

51 Summary and Outlook GROUP: Markus Arndt Q-enhanced Molecule Lithography Quantum-assisted Measurements Foundations of Quantum Physics Slit source array Diffraction Screen Proposal for tests of GRWP High mass High internal complexity Wide spatial separation G 1 G 2 Gring et al. Phys. Rev. A (2010) Juffmann et al. Phys. Rev. Lett. (2009) Gerlich et al. Angew. Chem. (2008) Tüxen et al. Eur. J. Org. Chem. (2011) Nimmrichter et al Phys. Rev. A 83, (2011).

52 KDTLI Molecular Quantum Nanophysics 2012 Theory Stefan Gerlich Sandra Eibenberger OTIMA Lukas Mairhofer Stefan Nimmrichter Far field Didactics Collaborations with: Marcel Mayor, Basel Mathias Tomandl Klaus Hornberger, Duisburg Ori Cheshnovsky, Tel Aviv Philipp Haslinger Philipp Schmid Ion Trap Nadine Dörre Johannes Horak Philipp Geyer SSPD Michele Sclafani Jonas Rodewald Stefan Kuhn Cavity Thomas Juffmann Peter Asenbaum Uzi Even, Tel Aviv Bernd von Issendorff, Freiburg Former experimental team: Hendrik Ulbricht, Southampton Lucia Hackermüller, Nottingham Nikos Doltsinis, Münster Anton Zeilinger, Vienna and many more

Decoherence in QM physics 491 fall 2009 friday feature M. Gold updated Oct. 1, 2015

diffraction experiment Decoherence in QM physics 491 fall 2009 friday feature M. Gold updated Oct. 1, 2015 In reality, it contains the only mystery, the basic peculiarities of all of quantum mechanics.