Exploring long-range interacting quantum many-body systems with Rydberg atoms

Transcription

1 Exploring long-range interacting quantum many-body systems with Rydberg atoms Christian Groß Max-Planck-Institut für Quantenoptik Hannover, November 2015

2 Motivation: Quantum simulation Idea: Mimicking one quantum system by another which is: cleaner, more controlled, better observable Motivation: Study fundamental questions of many-body physics. (Quantum) phase transitions, topology, quantum magnetism, out-of-equilibrium physics, thermalization, disorder,. in 1, 2 or 3 dimensions. Challenge: Design experiments to be described by a specific Hamiltonian: Theory and experiment often go hand-in-hand Feynman, Int. J. Theor. Phys Georgescu, Rev. Mod. Phys

3 Simulating solid-state systems Prime example: Optical lattices Solid-state Mott insulator (V2O3) Ultracold atomic Mott insulator Quantum simulators can explore fundamentally new many-body settings! 3

4 Why Rydberg atoms? Controlled long-range interactions Neutral ground state atoms state of the art: Feshbach tunable contact interactions Weak magnetic dipolar interactions Rydberg atoms: Strong dipolar interactions Interactions laser controlled and state selective Designable spatial dependence Applications in Q-simulation, Q-information and Q-metrology! 4

5 Examples of Rydberg Q-sim experiments Excitation transport Dissipative systems Günter, Science 2013 Malossi, PRL 2014 Spin chain dynamics Rydberg crystals Barredo, PRL 2015 Schauß, Science 2015 Note: List not complete 5

6 Outline Increasing complexity One lonely excitation: A scalable superatom Multiple excitations: Dynamics and spatial order Ground state physics: Dynamical crystallization The future: Rydberg dressing 6

7 The setting Single 2d sample Uniform laser coupling In-situ detection

8 The machine Laser table Main table Pictures: C. Lünig

9 The experimental setup Prepare atoms in single 2d plane Engineer initial density distribution Rydberg excitation Image the atoms Sherson, Nature

10 Site resolved imaging of ground state atoms Freeze the atomic distribution (ramp lattices to ~300 μk) 10

11 Site resolved imaging of ground state atoms Freeze the atomic distribution (ramp lattices to ~300 μk) 11 Use laser cooling (molasses) to induce fluorescence cool the atoms

12 Site resolved imaging of ground state atoms Freeze the atomic distribution (ramp lattices to ~300 μk) Use laser cooling (molasses) to induce fluorescence cool the atoms Imaging of Rydberg atoms: Be patient for a few more slides... 12

13 Local control of the atoms Focus laser beam on selected sites Use microwave to drive the spin flip Weitenberg, Nature

14 Writing atomic patterns Digital mirror device (DMD) to objective and atoms 14

15 Writing atomic patterns Digital mirror device (DMD) to objective and atoms 15

16 Ultimate initial state control Engineering the density distribution Initial Mott insulator DMD mask 16

17 Ultimate initial state control Engineering the density distribution Initial Mott insulator DMD mask 17 An atom cookie

18 Ultimate initial state control Engineering the density distribution Initial Mott insulator DMD mask 18 An atom cookie Precisely defined edge Total atom number 6dB below shot-noise

19 Rydberg superatoms Rb 68S J. Zeiher, P. Schauß, S. Hild, T. Macrì, I. Bloch, and C. Gross, Phys. Rev. X 5, (2015)

20 A normal atom (0.5 μm)

21 A normal atom (0.5 μm)

22 A Rydberg atom (250 μm)

23 Rydberg atoms Highly excited atoms Hydrogen-like wavefunction Saffman, Rev. Mod. Phys

24 Rydberg atoms Highly excited atoms Hydrogen-like wavefunction Extreme interactions (huge polarizability) (van der Waals: dipole-dipole: ) Saffman, Rev. Mod. Phys

25 Rydberg atoms Highly excited atoms Hydrogen-like wavefunction Extreme interactions (huge polarizability) (van der Waals: dipole-dipole: ) Tunability! Saffman, Rev. Mod. Phys

26 The dipole blockade Two photon laser coupling Laser parameters: Rabi frequency: Detuning Jaksch, PRL 2000 Lukin, PRL

27 The dipole blockade Two photon laser coupling Interaction exceeds all relevant Laser parameters: Rabi frequency: Detuning energy scales on μm scales! Blockade radius: Jaksch, PRL 2000 Lukin, PRL

28 Driving a superatom Extreme nonlinearity: At most one excitation Symmetry! Coupling to W-state 28

29 Driving a superatom Extreme nonlinearity: At most one excitation Symmetry! Coupling to W-state Signature of a superatom scaling of the Rabi frequency 29

30 Many experiments already... Paris (Browaeys, Grangier) Gaetan, Nat. Phys Atlanta (Kuzmich) Dudin, Nat. Phys Madison (Saffman) Ebert, PRL 2014

31 Imaging single Rydberg atoms Quantum gas microscope 31

32 Imaging single Rydberg atoms Coupling Quantum gas microscope 32

33 Imaging single Rydberg atoms Coupling Blowout Quantum gas microscope 33

34 Imaging single Rydberg atoms Coupling Blowout De-pumping Quantum gas microscope Detection efficiency: 65% 34

35 Rabi oscillations 1 atom 35

36 Rabi oscillations 1 atom 8 atoms 36

37 Rabi oscillations 1 atom 8 atoms 18 atoms 37

38 Rabi oscillations 1 atom 8 atoms 18 atoms 41 atoms 38

39 Rabi oscillations 1 atom 8 atoms 18 atoms 41 atoms 85 atoms 39

40 Rabi oscillations 1 atom 8 atoms 18 atoms 41 atoms 85 atoms 130 atoms 40

41 Rabi oscillations 1 atom 8 atoms 18 atoms 41 atoms 85 atoms 130 atoms 186 atoms 41

42 Scaling the superatom Fitted exponent 0.48±0.10 W-state scaling between 1 and 190 atoms 42

43 Breaking the dipole blockade Largest system 15x15 sites (186 atoms) Decay time: 0.34μs 43

44 Breaking the dipole blockade Largest system 15x15 sites (186 atoms) Decay time: 0.34μs Double Rydberg events 44

45 Breaking the dipole blockade Largest system 15x15 sites (186 atoms) Decay time: 0.34μs Only single Rydberg events Decay time: 0.91μs Double Rydberg events 45

46 Exploring the transverse Ising Model with long-range interactions Rb 43S P. Schauß, M. Cheneau, M. Endres, T. Fukuhara, S. Hild, A. Omran, T. Pohl, C. Gross, S. Kuhr, and I. Bloch, Nature 491, 87 (2012)

47 Seriously breaking the blockade Let's drive Rabi oscillations. 47

48 Frozen gas Rydberg physics Dynamics on sub-μs timescales no atomic motion 48

49 Long-range interacting transverse Ising model 49

50 A closer look to the data Superposition of different many-body states 50

51 A closer look to the data Superposition of different many-body states 51

52 Emerging spatial order Post select according to the number of excitations Single shot Ensemble ne=2 ne=3 ne=4 ne=5 52

53 Emerging spatial order Post select according to the number of excitations Single shot Ensemble Ensemble aligned Theory ne=2 ne=3 ne=4 ne=5 53

54 The blockade radius Distance correlations between Rydberg atoms Imperfections: 54 Hopping during detection: 1% Hopping before detection: 0.5μm Finite blow out: 0.2 atoms/image

55 Sweeped excitation: Adiabatic ground-state preparation Picture: van Bijnen, J. Phys. B: At., Mol. Opt. Phys P. Schauß, J. Zeiher, T. Fukuhara, S. Hild, M. Cheneau, T. Macrì, T. Pohl, I. Bloch, and C. Gross, Science 347, (2015)

56 The ground state phase diagram 56

57 Dynamical crystallization Coherent control of many-body systems through adiabatic sweeps 57

58 Tracking the crystallization 1D chains 58

59 Tracking the crystallization 1D chains 59

60 Tracking the crystallization 1D chains 60

61 Tracking the crystallization 1D chains 61

62 1D Rydberg chains: Different lengths Goal: measure crystal compressibility Excitations vs. detuning: Excitations vs. length: 62

63 1D Rydberg chains: Different lengths Goal: measure crystal compressibility Excitations vs. detuning: Excitations vs. length: DMD cutting: Keep 3xN sites 63

64 1D Rydberg chains: Different lengths Goal: measure crystal compressibility Excitations vs. detuning: Excitations vs. length: DMD cutting: Keep 3xN sites 64

65 Rydberg crystals compressibility Rydberg excittion number vs. chain length 65

66 Rydberg crystals compressibility Rydberg excittion number vs. chain length Plateaus of equal height Vanishing compressibility on the plateaus 66

67 2D Rydberg crystals Sweeped excitation localizes the excitations! No sweep Sweep, small cloud 67 Sweep, large cloud

68 2D Rydberg crystals Sweeped excitation localizes the excitations! No sweep Sweep, small cloud Sweep, large cloud Some single shots 68

69 2D Rydberg crystals Sweeped excitation localizes the excitations! No sweep Sweep, small cloud Sweep, large cloud Some single shots 69

70 The future: Rydberg dressing New directions for quantum simulations Flexible spin models Supersolids Glaetzle, PRL 2015 van Bijnen, PRL 2015 Henkel, PRL 2010 Pupillo, PRL And more: Dipolar Fermions Dauphin, PRA 2012 Xiong, PRA 2014 Li, Nat. Comm Quantum metrology Bouchoule, PRA 2002 Gil, PRL 2014

71 Rydberg dressing concepts Admix a little bit of Rydberg to the ground state Admixture Lifetime Interaction Bouchoule, PRA 2002 Henkel, PRL 2010 Pupillo, PRL 2010 Honer, PRL (2010) Johnson, PRA (2010) 71

72 Rydberg dressing concepts Admix a little bit of Rydberg to the ground state Admixture Lifetime Interaction Requires high Rabi frequency! Bouchoule, PRA 2002 Henkel, PRL 2010 Pupillo, PRL 2010 Honer, PRL (2010) Johnson, PRA (2010) 72

73 Rydberg dressing concepts Admix a little bit of Rydberg to the ground state Admixture Lifetime Interaction Direct UV coupling! Requires high Rabi frequency! Bouchoule, PRA 2002 Henkel, PRL 2010 Pupillo, PRL 2010 Honer, PRL (2010) Johnson, PRA (2010) 73

74 Revealing the interaction potential Probing via Ramsey interferometry Rel. pulse height At short times: phase ~ interactions Directly image the dressing potential Time (μs) state feels pair potential Ising Hamiltonian

75 Rydberg dressing first signs Correlation map Raw image Vert. shift (pix) Hor. shift (pix) 5 PRELIMINARY 75

76 Rydberg dressing first signs Correlation map Raw image Vert. shift (pix) Hor. shift (pix) 5 Dressing time (μs) PRELIMINARY 18 Inducing a long range potential works! 76

77 Summary Scalable superatoms Multiple excitations Dynamics Rydberg crystals Rydberg dressing First steps The team Theory T. Yefsah J. Zeiher S. Hild R.v.Bijnen J.-Y. Choi S. Hollerith I. Bloch T.Pohl P. Schauß T. Fukuhara M. Cheneau

78 Starting 2016: RyD-QMB (= Rydberg dressed quantum many-body physics) Starting Grant 2015 Developing a new Q-sim platform: Rydberg dressing with potassium Goals: Flexible spin models Supersolids Glaetzle, PRL 2015 van Bijnen, PRL 2015 Henkel, PRL 2010 Pupillo, PRL

79 Starting 2016: RyD-QMB (= Rydberg dressed quantum many-body physics) Starting Grant 2015 Developing a new Q-sim platform: Rydberg dressing with potassium Interested in a PhD project? Contact me! Goals: Flexible spin models Supersolids Glaetzle, PRL 2015 van Bijnen, PRL 2015 Henkel, PRL 2010 Pupillo, PRL