Single-Photon Atomic Cooling - Raizen Lab - The University of ...

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y the one-way-wall through an irreversible step. The one-way-wall continues to sweep until all atoms have encountered it, been cooled and returned to the center of the conservative potential. This general technique is applied, for the first time, to the specific case of cooling magnetically trapped 87 Rb, and details of its specific implementation and results are given in Ch. 4. 1.5 Single-Photon Cooling as a Maxwell’s Demon In 1867 James Clerk Maxwell proposed the notion of a “very observant and neat-fingered being” and wondered if under certain circumstances it could possibly violate the second law of thermodynamics [24]. He imagined such a creature, later given the honorable designation of a “Maxwell’s Demon” by Lord Kelvin [25], as operating a trap door separating two halves of a vessel filled with gas molecules initially in thermal equilibrium. He argued that if the demon sensed the velocity of molecules at they approached and directed fast- moving molecules into one half of the vessel and slow-moving molecules into the other half it would cause a temperature differential “without expenditure of work.” A second version of the demon would simply let molecules pass into one half of the vessel but never out of it, thus developing a pressure differential. Such apparent violations of the second law of thermodynamics spurred intense interest and research into “exorcising” such demons, in other words demonstrating that they do not violate any microscopic or macroscopic law of physics. One enduring notion, originally proposed by Szilard [26], and later 16
worked on by Brillouin [27–29], identified the information obtained by the demon, which it used to determine the appropriate action of the trap door, as having physical entropic content. This concept effectively exorcised such Maxwell Demons because the entropy associated with the information gathered by the demon is never less than the reduction of entropy due to the demon’s actions. This notion of information carrying entropy has become a key concept in information theory ever since [30–33]. Despite the fact that the work done by Szilard and others demonstrated that such processes do not violate any physical law, any proposal or experiment in this vein has been continued to be called a Maxwell’s Demon. Single-photon cooling is an optical realization of a Maxwell’s Demon. An atomic ensemble confined in a conservative potential is directly analogous to the ‘gas in a vessel.’ The demon analog, however, is not simply the one-way- wall alone. Rather, it is the combination of the one-way-wall and its carefully selected slow sweep through the trapped atomic ensemble. The information gathered by the demon is the single photon spontaneously scattered by each atom as it transits the barrier. To make things a little more concrete, consider the action of the single-photon cooling process on a non-interacting atomic ensemble with the well defined energy distribution fE defined such that n(E) = NfE dE (1.4) where N is the total number of atoms, and n(E) is the number of atoms with energy between E and E+dE. Figure 1.7(a) shows such an energy distribution 17
Page 1 and 2: Copyright by Gabriel Noam Price 200
Page 3 and 4: Single-Photon Atomic Cooling by Gab
Page 5 and 6: Acknowledgments First, I would like
Page 7 and 8: Rubidium group when I first joined.
Page 9 and 10: Single-Photon Atomic Cooling Public
Page 11 and 12: 2.5.2.4 Magneto-Optical Trap . . .
Page 13 and 14: List of Tables 2.1 87 Rb Physical P
Page 15 and 16: 3.1 Vacuum Chamber . . . . . . . .
Page 17 and 18: Chapter 1 Introduction This chapter
Page 19 and 20: the momentum kicks due to absorptio
Page 21 and 22: samples by allowing for very long i
Page 23 and 24: Figure 1.2: The energy level struct
Page 25 and 26: quency regime [19]. This then led t
Page 27 and 28: Figure 1.4: Depiction of a simple,
Page 29 and 30: demonstrates the cooling power of a
Page 31: a) b) c) external potential one-way
Page 35 and 36: the atomic ensemble. Not surprising
Page 37 and 38: are untrappable. The SI unit for en
Page 39 and 40: the atomic transition and is called
Page 41 and 42: 2.1 Rubidium Rubidium (Rb) is an al
Page 43 and 44: constant which is given by α = e2
Page 45 and 46: only one value of J is possible fro
Page 47 and 48: the latter of which only applies to
Page 49 and 50: Figure 2.1: 87 Rb D2 Transition Hyp
Page 51 and 52: Pluging Eq. 2.18 into this Hamilton
Page 53 and 54: Following the same logic leads to a
Page 55 and 56: gF = −1/2 using the approximate e
Page 57 and 58: mize their energy in high magnetic
Page 59 and 60: If we now consider the field from t
Page 61 and 62: where P is in torr. The lifetime of
Page 63 and 64: component of the dipole oscillation
Page 65 and 66: maxima. Our experiment makes extens
Page 67 and 68: atoms its wavefunction Ψ(t) is typ
Page 69 and 70: In this equation we let H = H0 + Hc
Page 71 and 72: The significance of Isat is that at
Page 73 and 74: Δ ω =ω−Δ ω =ω−Δ Δ
Page 75 and 76: where I/Isat ≪ 1 has been assumed
Page 77 and 78: λ λ Figure 2.9: The Sisyphus cool
Page 79 and 80: process repeats. If however, it dec
Page 81 and 82: σ σ σ Figure 2.10: Geomet
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to vary linearly with position alon
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0, ±1 and ∆mF = 0, ±1, allow ex
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this figure only the relevant hyper
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D2 transition in 87 Rb has a natura
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2.7.2 Saturation Absorption Spectro
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ground state depletion due to the p
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oadened background can be removed f
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where n is the number density of at
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where σ 2 c = σ 2 2 kBTt n + m .
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Chapter 3 Experimental Apparatus Th
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Figure 3.1: The vacuum chamber duri
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Nor-Cal Products Inc. (AMV-1502-CF)
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and monitor the necessary vacuum le
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3.1.3 Lower Chamber The lower chamb
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a) top ridge 1 cm b) metal jacket h
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to the appropriate frequency throug
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plexiglass cover piezo U stack grat
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λ Figure 3
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Voltage a b c d e f Frequency Figur
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eams. For example the MOT and optic
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λ Figure 3.12: The slave lasers
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λ λ λ
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λ λ λ λ
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needed when forming a MOT or optica
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master laser is dithered at 20 kHz.
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λ λ
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Output Power > 10 W Wavelength 532
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labeled 1, 2 and 3 in the Fig. 3.21
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λ λ λ λ
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process. The two coils are arranged
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19) connected in parallel. This arr
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3.4.2 Horizontal Imaging The horizo
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Chapter 4 Single-Photon Atomic Cool
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1 s, after which time ∼ 10 8 87 R
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(a) x z magnetically trapped atoms
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h x z magnetically trapped atoms y
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z y x magnetically trapped atoms cr
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Figure 4.5: The effective potential
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depopulation present and it indicat
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numbers sufficiently large to quant
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μ μ μ
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the potential landscape due to the
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Figure 4.12: The number of atoms lo
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Figure 4.13: Incremental atom captu
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netic trap and transfer into the op
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temperature TB of atoms loaded into
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used to construct it into the remai
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μ μ μ Figure 4.18: Side view of
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Figure 4.20: Geometry of the optica
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could potentially have undergone th
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detunings. The result of scattering
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are switched off causing non-optica
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Figure 4.25: Number (■) and tempe
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traps. If we model the ensembles in
Page 191 and 192:
Figure 4.26: Radius of the atomic c
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atoms were removed from the magneti
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trappable |F = 1,mF = −1〉 state
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the short lived 2p state. Atoms whi
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Bibliography [1] R. Frisch, “Expe
Page 201 and 202:
[15] C. C. Bradley, C. A. Sackett,
Page 203 and 204:
[31] E.T. Jaynes, “Information th
Page 205 and 206:
[49] J. Ye, S. Swartz, P. Jungner,
Page 207 and 208:
[66] J.P. Gordon and A. Ashkin, “
Page 209 and 210:
[85] C.-S. Chuu, Direct Study of Qu
Page 211 and 212:
adicals,” Phys. Rev. Lett. 94, 02
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