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Grad map 2015-04-18

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Grad map 2015-04-18

  1. 1. Atomic, Molecular and Optical Physics: A Tool to Reveal and Harness Nature’s Most Cherished Secrets Wendell T. Hill, III Joint Quantum Institute University of Maryland April 18, 2015 GRAD-MAP Spring Symposium UMD
  2. 2. Harnessing & Exploring Nature AMO Improving Health AMO Protecting the Environment AMO Impacting the EconomyAMO Enhancing Defense AMO Expanding the Frontiers http://www.nap.edu/catalog/10516/atoms-molecules-and-light-amo-science-enabling-the-future
  3. 3. The “ultras” and the frontier of physics Dynamics at ultrashort times Dynamics at ultrahigh intensities
  4. 4. The “ultras” and the frontier of physics Dynamics at ultralow temperatures Outline What can we learn with: • attosecond (10-18 sec) laser pulses? • intensities in excess of 1023 W/cm2? • collections of atoms with temperatures in 10-9 K range?
  5. 5. Frozen Motion Characteristic TimescalesIn 1872: 0.5 ms (0.5×10-3 s) The beginning of ultrafast studies Eadweard Muybridge's famous "Horse in Motion” to solve a bet.
  6. 6. Watching dynamics Science 312, 424 (2006) Phys. Chem. Chem. Phys.13, 8331 (2011) Requires femtoseconds Requires attoseconds Watch electron dynamicsWatch nuclear dynamics
  7. 7. Hydrogen atom (Z=1) t ~ 24 as
  8. 8. Ultrashort laser pulses DtDn »1 Few cycles Many frequencies I µ E 2 Ultraviolet & X-rays T =1 n = l c
  9. 9. Hydrogen atom (Z=1) Fa = 5.14´109 V/cm Þ Ia = 3.5´1016 W/cm2
  10. 10. The problem Intense pulses can move states around and induce synthetic, time-dependent decay channels
  11. 11. Intensity Eras Dark matter might be revealed!
  12. 12. Quantum gas Cooling BEC
  13. 13. • Fundamental interactions can be described in terms of gauge symmetries of free particles: The photon, for example is responsible for the electromagnetic force. • All the forces have propagators – particles mediating the force. Open questions such as the origin of forces, in principle can be investigated with a cold atom simulator of so-called dynamic gauge fields. Artificial Gauge Fields e- e-g BEC 1 BEC 1 BEC2
  14. 14. Conclusion The goals of AMO science, however, are not just to generate “ultras,” but to understand atoms and light at their deepest level, to probe the fundamental laws of physics, to push the frontiers of our understanding, and to develop new techniques for measuring and manipulating light and matter. AMO research studies the basic symmetries of nature; the properties of space and time; unexplored aspects of quantum mechanics; the interaction of matter and light under extreme conditions; the structure and interactions of atoms and molecules; new forms of matter such as coherent atoms and superfluid atomic gases; and the deep connections between physics and information. Basic research often leads to totally unexpected applications, and while it is too early to judge the ultimate payoffs that may result from the advances and developments reported in this chapter, the joyful quest for knowledge and the promise of new technologies continue to drive and animate AMO science. cira 2000
  15. 15. • Grad Students – Jie Zhu, Kun Zhao, Lee Elberson, Vishal Chintawar and Guan-Yeu Chen, Davy Foote. • Postdocs & Visitors – Zhenwei Wang, Getahun Menkir, Guizhong Zhang Hyounguk Jang and Jane Lee. • Undergrad Students – Marcus Laich, Phillip Land and Seth Iacangelo, Ben Crist. • Support Acknowledgements J. Lee
  16. 16. The Fellowship of the Ring NIST Na BEC I Steve Eckel (JQI postdoc) Avinash Kumar (UMD student) Fred Jendrzejewski (JQI postcoc) William D. Phillips (NIST) Gretchen K. Campbell (NIST) Jeff Lee (UMD student) Chris J. Lobb (UMD Faculty) Wendell Hill (UMD Faculty) Former Members Kevin C. Wright (JQI postdoc) R. Brad Blakestad (JQI postdoc) Anand Ramanathan(UMD student) Theory Collaborators Ludwig Mathey (JQI postdoc) Amy Cassidy (JQI postdoc) Charles Clark (NIST) Mark Edwards (Georgia Southern) AvinashJeff Bill Gretchen Chris Steve Fred
  17. 17. The End
  18. 18. g
  19. 19. Physics at its Fundamental Level • The Standard Model of fundamental particles and interactions Explains a lot of what is observed but has problems: – Predicts neutrinos to be massless, but can be fixed to account for the observed mass. – Does not appear to account for imbalance between matter and antimatter observed; why are there more electrons in the universe than positrons? – Does not appear to account for Dark Matter and Dark Energy
  20. 20. Physics at its Fundamental Level • The Standard Model of fundamental particles and interactions Explains a lot of what is observed but has problems: – Predicts neutrinos to be massless, but can be fixed to account for the observed mass. – Does not appear to account for Dark Matter and Dark Energy – Does not appear to account for imbalance between matter and antimatter observed; why are there more electrons in the universe than positrons? Requires CP violation beyond what model predicts.
  21. 21. CPT Invariance • Appropriate models require CPT invariance – Charge conjugation (C): changing the sign of the charge and all other internal quantum numbers; turns particles into their antiparticle. Quantities like mass, spin do not change. – Parity (P): ; right handed coordinate system goes to a left handed system. – Time (T): • Either all three can be invariant or if one changes signs then the other pair as a group must also change signs. • Consider the electron as a point charge r ®-r t ®-t + -
  22. 22. CPT for Electron • C: charge changes from -e to +e. (sign change) • P: nothing changes. (no sign change) • T: spin changes signs. (sign change) • CPT (-CP)(-T) = CPT (invariant!) • One solution to the imbalance problem is an EDM of e. ®
  23. 23. Electron EDM Time Reversal Parity t ®-t r ®-r T -T and P -P, which means that CP -CP so that CPT is invariant!® ® ® Models beyond the Standard Model allow for more CP violation, thus there are several EDM experiments using atoms, molecules and nuclei. See, for example: http://laserstorm.harvard.edu/edm/, http://www.yale.edu/lamoreauxgroup/, http://www.physicsjazz.info/edm/lbnl/, http://www3.imperial.ac.uk/ccm/research/edm
  24. 24. + - + - t ®-t + -+ - r ®-r
  25. 25. Chen et al., PRA 79, 011401(R) (2009). Optimal Solutions for Enhancements CO2 During Dissociative Ionization
  26. 26. Optimal Solutions for Bending Amplitude Enhancement of CO2 During Dissociative Ionization Chen et al., PRA 79, 011401(R) (2009).
  27. 27. A basic control problem where x0 is the initial condition on x and a is a control parameter. In this case, one looks for x(t) while holding a fixed. Assume we have an ordinary differential equation of the form, x t( ) = f x t( ),a( ) t > 0 x 0( ) = x0 , ì í ï îï
  28. 28. Basic problem More generally, there will be a family of parameters, which are appropriate within different time intervals. We are thus interested in solving x t( ) = f x t( ),a t( )( ) t > 0 x 0( ) = x0 , ì í ï îï
  29. 29. System trajectory Adopted from: An Introduction to Mathematical Optimal Control Theory Version 0.2 Lawrence C. Evans, http://math.berkeley.edu/~evans/control.course.pdf.
  30. 30. Reaching the target There must be a well-defined payoff for reaching a designated end point or taking a preferred path. Thus one defines a fitness functional: = dt t=0 t=T ò f x t( ),a t( )( )ÄC t( ) Þ Extremum were are possible system constraints.C t( ) ξ
  31. 31. Adjust Control Parameters Each individual is composed of a set of genes, gi, four in this case. N (~40) individuals in one generation Gaussian distributed random number center at initial guess INI3I1 2g 1g 3g 4g I2 2g 1g 3g 4g 2g 1g 3g 4g 2g 1g 3g 4g
  32. 32. Set Experimental parameters Pulse Shaper: Zero order stretcher and spatial light modulator
  33. 33. Science 303, 1998 (2004)
  34. 34. Optimal Solutions for Controlling Dynamics Solutions contain well separated peaks with well-defined phase jumps! Enhanced Bending During Ionization Enhanced Branching Ratio CO2 6+ [CO2 5+] [CO2 6+]
  35. 35. HHG gas jets (atoms) 85 Kim & You, Nature Photonics 8, 92 (2014) ISUILS13 Session II Three step model: Ionization* Acceleration Recollision Recombination®
  36. 36. Attosecond “Streaking”
  37. 37. Transient Absorption of an Attosecond Pulse
  38. 38. Cooling & Trapping • Evaporative Cooling to BEC Level • Requires collisions to re-equilibrate while trap depth lowered to less than 1 μK.
  39. 39. Thermal vs quantum degeneracy • Key parameters: • Regimes: – Classical ideal gas – Quantum collisions – Quantum degenerate gas lTh = 2p 2 mkBT d @ n3 r0 lT << r0 << d r0 << lT << d r0 << d £ lT
  40. 40. BEC in atomic ideal gases* • 1924 – S. N. Bose proposed a new derivation of Planck’s law for black body radiation that was based on the number of microscopic states corresponding to macroscopic states for indistinguishable particles, and maximizing the entropy for a given energy [Z. Phys. 26, 178 (1924)]. – Applied to photons – the total energy is fix but the total number of photons is not fixed because photons can be absorbed and emitted. This leads to a single Lagrange multiplier related to the temperature, β = 1/kBT, and the Planck radiation law. *This discussion follows that outlined in Advances in Atomic Physics: An Overview, Cohen-Tannoudji and Guéry-Odelin, World Scientific (2011). “Theory of Bose-Einstein condensation in trapped gases,” Giorgini, Pitaevski and Stringari, Rev Mod Phys 71, 463 (1999).
  41. 41. BEC in atomic ideal gases (cont.) • 1924 & 1925 – Einstein extends Bose’s work to atoms [Sitzungsber. Preuss. Akad. Wiss., 261; Sitzungsber. Preuss. Akad. Wiss., 1]. – Applied to atoms – both the energy and the number of particles are fixed. This requires a second Lagrange multiplier, the chemical potential, μ, for the mean occupation number in state i is given by Total number For N0 ≥ 0, μ ≤ ε0 Ni = 1 e b ei-m( ) -1 N = giNi = i å gi e b ei-m( ) -1i å
  42. 42. BEC in atomic gases (cont.) The thermal component N = g0 e b e0-m( ) -1 + gi e b ei-m( ) -1i¹0 å N0 NTh NTh = gi e b ei-m( ) -1i¹0 å £ Nmax = gi e b ei-e0( ) -1i¹0 å m =e0 But, as with remaining finite!m ®e0, N0 ®¥ NTh So, if we let N get large with T and V fixed, more and more of the population will go into the ground state – a BEC.
  43. 43. BEC in atomic gases (cont.) • Now vary T (lower it) with N and V fixed: • The transition temperature occurs when gi e b ei-m( ) -1 ® 0, as b ®¥ ß NTh £ Nmax ® 0 Nmax = N N V =z 3 2( ) mkBTC 2p 2 é ëê ù ûú 3 2 =z 3 2( )lTh -3 Where is the Riemann zeta function.z 3 2( )= 2.6124
  44. 44. The hammer vs. scalpel Broad-band intense pulsed fields Narrow-band CW fields
  45. 45. Atomic structure of Alkali atoms
  46. 46. 87Rb
  47. 47. Cooling atoms with CW lasers
  48. 48. Temperature scale On this scale room temperature (STP) is ~ 300 STP 10-6 K Classical gas
  49. 49. Cooling and trapping • Dipole trap Polarization a = 6pe0c3 G w0 2 w0 2 -w2 -i w3 /w0 2 ( )G G = w0 3 e r12 2 3p c3 U r( )@ - 3pc2 2w0 3 G Dw Gsc = G Dw U r( ) p =aE A. Ashkin, PRL 40, 729 (1978) U = -p×E
  50. 50. np 2P3/2 ns 2S1/2 Visible to near IR Generic Alkali structure red detuned blue detuned U r( ) @ - 3pc2 2w0 3 G Dw Gsc = G Dw U r( ) A. Ashkin, PRL 40, 729 (1978)
  51. 51. Elements for atomtronics Atom tunnel [1] 1 mm [1] Y. Song, et al., Opt. Lett., 24 , 1808-1807 (1999); N. Chattrapiban, et al., Opt. Lett. 28, 2183-2185 (2003); Arakelyan, et al., Phys. Rev. A. 75, R17706 (2007) [2] J. Lee and W. T. Hill, III, Rev of Sci Instrum 85, 103106 (2014). Atom capacitor [2]
  52. 52. • Horizontal confinement – Blue 2D pattern ~ 60 μK. • Vertical confinement – blue light sheet ~ 500 μK, – gravity. Atomtronic capacitor with thermal 87Rb atoms 1 mm g Lee, et al., Sci. Rep. 3, 1034 (2013)
  53. 53. Capacitor experiment 5 ms 15 ms 25 ms 35 ms 45 ms 55 ms g Lee, et al., Sci. Rep. 3, 1034 (2013)
  54. 54. Classical idea gas experiment -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0 10 20 30 40 50 60 70 80 N/N0 Time (ms) Classical ideal gas capacitor decay w = 240 µm w = 384 µm w = 576 µm Lee, et al., Sci. Rep. 3, 1034 (2013)
  55. 55. Atomtronics vs. electronics Electrons: Atoms [2]: 2K ml L ne A C = Q V 2 f S p R nAe  Sharvin 3D [1] [1] Sharvin, Zh. Eksp. Teor. Fiz. 48, 984 (1965) [Sov. Phys. JETP 27, 655 (1965)]. Rc = 2 p ne w 1+ lw pA æ è ç ö ø ÷ LK = 2ml ne w S p R nw  2D Equivalent [2] Lee, et al., Nature Sci. Rep. 3, 1034 (2013).
  56. 56. Temperature scale On this scale room temperature (STP) is ~ 300 STP 10-9 K STP 10-6-10-9 Quantum gas
  57. 57. BEC in atomic gases (cont.) T ³ TC N0 » 0 (thermodynamic limit) T < TC N0 N =1- T TC æ è ç ö ø ÷ 3 2 JILA 1st BEC observation
  58. 58. BEC RLC circuit In-situ images of BEC atoms 300K atoms contained in a blue-detuned potential of ~ 1 kHz height. The first image taken 5 ms after the gate blocking the flow is removed, with 20 ms between each subsequent frame.
  59. 59. Discharging capacitor quantum vs. classical BEC (superfluid) Case Ideal Gas Case -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0 20 40 60 80 N/N0 Time (ms)
  60. 60. BEC RLC circuit In-situ images of BEC atoms Vortex generation during flow 300K atoms contained in a blue-detuned potential of ~ 1 kHz height. The first image taken 5 ms after the gate blocking the flow is removed, with 20 ms between each subsequent frame. Vortex-like excitations appear in the initially empty reservoir ~600 ms after discharge, showing evidence of the Feynman mechanism for dissipation in the atom circuit.
  61. 61. Quantized current n=0 n=1 n=2 n=3 n=4 n=0 n=1 n=3n=2
  62. 62. 0 1 2 3 0 1 2 3 W/2p (Hz) Averagecirculation Discrete phase slips between current states 0→1 1→2 Ub≈0.5 m Each data point represents the average of many shots
  63. 63. Superfluid discharge Coherent (Feynman) Dissipation [1] Ballistic (Sharvin) Resistance [2] [1] Sharvin, Zh. Eksp. Teor. Fiz. 48, 984 (1965) [Sov. Phys. JETP 27, 655 (1965)]. [2] R. Feynman, Progress in Low Temperature Physics 1, 17 (1955).
  64. 64. Things to do with BEC atoms Quantized vortices Optical lattices
  65. 65. • Fundamental interactions can be described in terms of gauge symmetries of free particles: The photon, for example is responsible for the electromagnetic force. • All the forces have propagators – particles mediating the force. Open questions such as the origin of forces, in principle can be investigated with a cold atom simulator of so-called dynamic gauge fields. Artificial Gauge Fields e- e-g BEC 1 BEC 1 BEC2

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