Rydberg excitation in thermal vapor cells. Pisa Sept, 18 th Robert Löw

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1 Universität Stuttgart Robert Löw 5. Physikalisches Institut Rydberg excitation in thermal vapor cells Pisa Sept, 18 th Robert Löw

2 Outline Strongly interacting Rydberg gases ultracold Rydberg atoms in thermal vapors - Spectroscopy cells - Rydberg wall interactions - Pulsed Rydberg excitation - Rydberg-Rydberg interaction at room temperature - 4 wave mixing - Direct measurment of Rydberg states - RF- sensing

3 The interactions between Rydberg states are strong long-range tunable switchable anisotropic and can be used M. Saffman et al., Rev. Mod. Phys. 82, 2313 (2010) for neutral atom quantum computing and quantum simulation as long range and anisotropic interaction potentials for quantum degenerate gases as an optical non-linearity on the single photon level

4 Interaction between Rydberg atoms V e R R r 2 r1 R r 2 R r1 r r 3 r 1 R r 2 R e Dipole-dipole interaction 3 5 R R

5 New interactions! 44D C6 vdw: E C MHz m r 3 3 dip-dip: E 1 sin 1600 MHz m r

6 T. Förster, Z. Naturforsch 4a, 321 (1949) Förster energy transfer

7 T. Förster, Z. Naturforsch 4a, 321 (1949) Förster Resonance See work by Gallagher, Pillet, Raithel, Ryabtsev, Martin, Weidemüller etc.

8 Interaction between Rydberg atoms Förster resonance: tune D to zero Dipolar interaction for R 1 2 dd 3 D sign depends on D!

9 Excitation blockade by van der Waals interaction C r 6 / 6 Length scale of the Rydberg-Rydberg interaction: r b C m Distance between two atoms

10 Excitation blockade by van der Waals interaction Distance between to atoms

11 Collective state 1 E ryd, g, g,..., g g, ryd, g,..., g... g, g,..., g, ryd N N G g, g, g,..., g 0 Super tom

12 Excitation dynamics in an inhomogeneous Rydberg gas 5 m 1000 Atoms 300 nm No atomic motion during excitation: Frozen Rydberg gas!

13 Excitation dynamics in an inhomogeneous Rydberg gas 5 m 1000 Atoms 300 nm No atomic motion during excitation: Frozen Rydberg gas! PRL 99, (2007)

14 Is it Crystaline? d

15 Is it Crystaline? d Second order phase transition

16 Effective Spin Hamiltonian H d 2 2 P P ( i) ( j) ( i) ( i) ee ee z x C6 6 i i j i ri rj d Phase diagram Projector: P (1 ) / 2 ( i) ( i) ee z Quantum critical region PRL (2008) J Phys B, (2012)

17 Miniaturization 5. Phys. Inst. Rydberg BEC primary-frequency-standards.cfm

18 Miniaturization thermal vapor 20 µm 5. Phys. Inst. Rydberg BEC primary-frequency-standards.cfm 15 mm

19 Miniaturization thermal vapor 20 µm 5. Phys. Inst. Rydberg BEC primary-frequency-standards.cfm 15 mm Entangle cells Create a photon Destroy a photon

20 Perspectives for QIP with hot Rydberg atoms Artificial Atoms Artificial Quantum Dots Quantum dot Single exciton Size ~10-20 nm Low temperature Hard to control nuclear spins Shorter spin coherence times Epitaxial growth Positioning is tricky Micro cell (size < a block ) Single Rydberg excitation Size > l opt Room temperature Pure nuclear spin states Long spin coherence times Photolithography Easy positioning

21 What do we need? Micro cells Fabrication method for microscopic vapor cells for alkali atoms T. Baluktsian, et al., Opt. Lett. 35, 1950 (2010) confinement of the atoms < a block Narrow lines width << hyperfine splitting Coherent excitation of Rydberg atoms in micrometre-sized atomic vapor cells H. Kübler, et al., Nature Photonics 4, 112 (2010) Coherent dynamics thermal vapor GHz Rabi flopping to Rydberg states in hot atomic vapor cells B. Huber, et. al., PRL 107, (2011) excitation on the ns timescale Interaction Rydberg blockade Evidence for strong van der Waals-type Rydberg-Rydberg interaction in thermal vapor, submitted

22 Cover method Rb-Reservior optical bond + quartz solder

23 Micro - cells 1 µm 40 µm 10 µm 10 µm 20 µm T. Baluktsian, C. Urban, T. Bublat, H. Giessen, R. Löw, and T. Pfau "Fabrication method for micro vapor cells for alkali atoms" Opt. Lett. 35, 1950 (2010)

24 Absorption spectroscopy in a 10 µm vapor layer Absorption spectra Optical density 10 µm Calculated from Rb vapor pressure model 85 Rb 5S 1/2 F=3 5P 3/2 F=4 Opt. Lett. 35, 1950 (2010)

25 Coherent Rydberg excitation EIT Scheme 32S, 41D, 43S 200 µm Coupling 480 nm 50 mm 5P Probe 780 nm 5S

26 Coherent Rydberg excitation

27 Wall interactions!!! Image charges Charges Surface polaritons

28 Resonant energy transfer to Quartz walls by surface polaritons Spitzer and Kleinman, Infrared Lattice Bands in Quartz, Phys. Rev., (1961)

29 Resonant coupling to infrared surface polaritons 18P 17P µm µm µm 43S 13P Infrared Lattice Bands in Quartz Spitzer and Kleinman Phys. Rev. 121, 1324 (1961) 18P µm µm µm µm 41D µm 16F

30 Avoid resonant coupling to infrared surface polaritons Nature Photonics 4, 112 (2010)

31 Rydberg EIT in 1 µm vapor layer Nature Photonics 4, 112 (2010)

32 Freezing hot atoms cold: cm 1 s 10 µs = 100 nm hot: m 100 s 1 ns = 100 nm

33 Pulsed excitation of Rydberg states 480 nm 780 nm

34 Power dependence of oscillations Ω eff Ω Ω [MW/cm²]

35 Power dependence of oscillations Ω eff Ω Ω [MW/cm²] Simulations Rydberg occupation with velocity distribution PRL 107, (2011) 12 p-pulse in 4 ns only limited by pulse length!

36 Ground - Rydberg Rabi oscillations red transmission simulation simulated Rydberg occupation

37 Dephasing due to interactions 20 times higher density

38 Dephasing due to interactions Systematic measurements n = 37 densities in the range of Rydberg states: Density [10 12 cm -3 ] 22S, 29S, 32S, 35S, 37S, 40S

39 Dephasing model for data fitting

40 Dephasing rates linear with density

41 Data collapse N eff crit C r 6 6 crit 1 r 3 crit

42 Dpehasing vs. principal quantum number n 11/ 2 n

43 A microscopic model

44 Van-der-Waals is effecitve at large bandwidth

45 Van-der-Waals is effecitve at large bandwidth?

46 How to create a photon

47 Superatom - 4 wave mixing Dipole pattern of 1 atom Dipole pattern of 100 phase matched atoms confined within 5 m

48 Single photons with ultracold atoms Y. O. Dudin and A. Kuzmich Science 2012 Also Vuletic, Adams

49 4 wave mixing Ψ > r Ψ > e1 Ω 480 ρ e1,r Ω 474 ρ r,e2 3 mm Ω 780 ρ g,e1 ρ e2,g Ψ > g Ψ > e2 k k 480 = k k 795

50 Simulation incl. Doppler broadening

51 Experiment PRA (2012)

52 Superatom - 4 wave mixing ns, nd 474 nm 480 nm 5P 3/2 5P 1/2 795 nm 780 nm 5S 1/2

53 Perspectives for integration

54 New cells Electrically contacted Electrically conductive coatings (ITO + SiN, ITO + SiOx, Al, Ni, Cr+Au) Production Process: Sputtering Photolithography Plasma Etching Gluing of the cell

55 Stark maps

56 Direct current measurement

57 Improved signal to noise Optical Current

58 Improved signal to noise

59 Current is linear with density

60 Highly resolved spectroscopy 42S state 1 Minute aquisition

61 Micro-wave sensing with Rydbergs

62 Achieved sensitivity Nature physics, online

63

64 Summary

65 Back to the cold outlook Excitation hopping in Rydberg Networks np> ns> R e> g>

66 Possible systems np> ns> 1 excitation + many network nodes : quantum random walk 1 < # excitations < # network nodes: 1d Bose gas np> ns> np> ns> # excitations ~ ½ # network nodes: spin chains

67 Hopping toolbox 1. Network preparation 2. excitation write 3. excitation read 4. controlled disorder

68 Dissipative many body quantum systems Coherent quantum dynamics in biological systems light harvesting complexes bioluminescence spectroscopic ruler

69 Thomas Baluktsian Daniel Barredo Renate Daschner Georg Epple Anita Gaj Bernhard Huber Andreas Kölle Harald Kübler Ralf Ritter Eva Schöll Alban Urvoy