Exploring long-range interacting quantum many-body systems with Rydberg atoms Christian Groß Max-Planck-Institut für Quantenoptik Hannover, November 2015
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. 1982 Georgescu, Rev. Mod. Phys. 2014 2
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
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
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
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
The setting Single 2d sample Uniform laser coupling In-situ detection
The machine Laser table Main table Pictures: C. Lünig
The experimental setup Prepare atoms in single 2d plane Engineer initial density distribution Rydberg excitation Image the atoms Sherson, Nature 2010 9
Site resolved imaging of ground state atoms Freeze the atomic distribution (ramp lattices to ~300 μk) 10
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
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
Local control of the atoms Focus laser beam on selected sites Use microwave to drive the spin flip Weitenberg, Nature 2011 13
Writing atomic patterns Digital mirror device (DMD) to objective and atoms 14
Writing atomic patterns Digital mirror device (DMD) to objective and atoms 15
Ultimate initial state control Engineering the density distribution Initial Mott insulator DMD mask 16
Ultimate initial state control Engineering the density distribution Initial Mott insulator DMD mask 17 An atom cookie
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
Rydberg superatoms Rb 68S J. Zeiher, P. Schauß, S. Hild, T. Macrì, I. Bloch, and C. Gross, Phys. Rev. X 5, 031015 (2015)
A normal atom (0.5 μm)
A normal atom (0.5 μm)
A Rydberg atom (250 μm)
Rydberg atoms Highly excited atoms Hydrogen-like wavefunction Saffman, Rev. Mod. Phys. 2010 23
Rydberg atoms Highly excited atoms Hydrogen-like wavefunction Extreme interactions (huge polarizability) (van der Waals: dipole-dipole: ) Saffman, Rev. Mod. Phys. 2010 24
Rydberg atoms Highly excited atoms Hydrogen-like wavefunction Extreme interactions (huge polarizability) (van der Waals: dipole-dipole: ) Tunability! Saffman, Rev. Mod. Phys. 2010 25
The dipole blockade Two photon laser coupling Laser parameters: Rabi frequency: Detuning Jaksch, PRL 2000 Lukin, PRL 2001 26
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 2001 27
Driving a superatom Extreme nonlinearity: At most one excitation Symmetry! Coupling to W-state 28
Driving a superatom Extreme nonlinearity: At most one excitation Symmetry! Coupling to W-state Signature of a superatom scaling of the Rabi frequency 29
Many experiments already... Paris (Browaeys, Grangier) Gaetan, Nat. Phys. 2009 Atlanta (Kuzmich) Dudin, Nat. Phys. 2012 30 Madison (Saffman) Ebert, PRL 2014
Imaging single Rydberg atoms Quantum gas microscope 31
Imaging single Rydberg atoms Coupling Quantum gas microscope 32
Imaging single Rydberg atoms Coupling Blowout Quantum gas microscope 33
Imaging single Rydberg atoms Coupling Blowout De-pumping Quantum gas microscope Detection efficiency: 65% 34
Rabi oscillations 1 atom 35
Rabi oscillations 1 atom 8 atoms 36
Rabi oscillations 1 atom 8 atoms 18 atoms 37
Rabi oscillations 1 atom 8 atoms 18 atoms 41 atoms 38
Rabi oscillations 1 atom 8 atoms 18 atoms 41 atoms 85 atoms 39
Rabi oscillations 1 atom 8 atoms 18 atoms 41 atoms 85 atoms 130 atoms 40
Rabi oscillations 1 atom 8 atoms 18 atoms 41 atoms 85 atoms 130 atoms 186 atoms 41
Scaling the superatom Fitted exponent 0.48±0.10 W-state scaling between 1 and 190 atoms 42
Breaking the dipole blockade Largest system 15x15 sites (186 atoms) Decay time: 0.34μs 43
Breaking the dipole blockade Largest system 15x15 sites (186 atoms) Decay time: 0.34μs Double Rydberg events 44
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
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)
Seriously breaking the blockade Let's drive Rabi oscillations. 47
Frozen gas Rydberg physics Dynamics on sub-μs timescales no atomic motion 48
Long-range interacting transverse Ising model 49
A closer look to the data Superposition of different many-body states 50
A closer look to the data Superposition of different many-body states 51
Emerging spatial order Post select according to the number of excitations Single shot Ensemble ne=2 ne=3 ne=4 ne=5 52
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
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
Sweeped excitation: Adiabatic ground-state preparation Picture: van Bijnen, J. Phys. B: At., Mol. Opt. Phys. 2011 P. Schauß, J. Zeiher, T. Fukuhara, S. Hild, M. Cheneau, T. Macrì, T. Pohl, I. Bloch, and C. Gross, Science 347, 1455 1458 (2015)
The ground state phase diagram 56
Dynamical crystallization Coherent control of many-body systems through adiabatic sweeps 57
Tracking the crystallization 1D chains 58
Tracking the crystallization 1D chains 59
Tracking the crystallization 1D chains 60
Tracking the crystallization 1D chains 61
1D Rydberg chains: Different lengths Goal: measure crystal compressibility Excitations vs. detuning: Excitations vs. length: 62
1D Rydberg chains: Different lengths Goal: measure crystal compressibility Excitations vs. detuning: Excitations vs. length: DMD cutting: Keep 3xN sites 63
1D Rydberg chains: Different lengths Goal: measure crystal compressibility Excitations vs. detuning: Excitations vs. length: DMD cutting: Keep 3xN sites 64
Rydberg crystals compressibility Rydberg excittion number vs. chain length 65
Rydberg crystals compressibility Rydberg excittion number vs. chain length Plateaus of equal height Vanishing compressibility on the plateaus 66
2D Rydberg crystals Sweeped excitation localizes the excitations! No sweep Sweep, small cloud 67 Sweep, large cloud
2D Rydberg crystals Sweeped excitation localizes the excitations! No sweep Sweep, small cloud Sweep, large cloud Some single shots 68
2D Rydberg crystals Sweeped excitation localizes the excitations! No sweep Sweep, small cloud Sweep, large cloud Some single shots 69
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 2010... And more: Dipolar Fermions Dauphin, PRA 2012 Xiong, PRA 2014 Li, Nat. Comm. 2015 Quantum metrology Bouchoule, PRA 2002 Gil, PRL 2014
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
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
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
Revealing the interaction potential Probing via Ramsey interferometry Rel. pulse height 1 0.8 At short times: phase ~ interactions Directly image the dressing potential 0.6 0.4 0.2 0 0 40 80 Time (μs) 120 74 state feels pair potential Ising Hamiltonian
Rydberg dressing first signs Correlation map Raw image Vert. shift (pix) 5 2 0-5 9-5 0 1 Hor. shift (pix) 5 PRELIMINARY 75
Rydberg dressing first signs Correlation map Raw image Vert. shift (pix) 5 2 0-5 9-5 0 1 Hor. shift (pix) 5 Dressing time (μs) 0 4 7 PRELIMINARY 18 Inducing a long range potential works! 76
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
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 2010... 78
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 2010... 79