Взаимодействие одиночных атомов с сильно сфокусированным световым полем - PDF

Взаимодействие одиночных атомов с сильно сфокусированным световым полем Syed Abdullah Aljunid, Jianwei Lee, Brenda Chng, Martin Paesold, Dao Hoang Lan, Teo Zhi Wei Colin*, Kadir Durak, Gleb Maslennikov,

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Взаимодействие одиночных атомов с сильно сфокусированным световым полем Syed Abdullah Aljunid, Jianwei Lee, Brenda Chng, Martin Paesold, Dao Hoang Lan, Teo Zhi Wei Colin*, Kadir Durak, Gleb Maslennikov, Valerio Scarani*, Christian Kurtsiefer Former members: Meng Khoon Tey, Zilong Chen, Timothy Liew*, Florian Huber Motivation Quantum Information and Communication protocols information exchange between flying qubits (photons) and stationary qubits (atoms) absorption triggered phase shift EFFICIENCY OF ATOM-PHOTON INTERFACE Basic Problem Get strong coupling between an atom and a light field on the single photon level electromagnetic field / photon -level atom Use a cavity ( ) High electrical field strength even for a single photon Preferred spontaneous emission into the cavity mode A cavity can enhance the interaction between a propagating external mode and an atom Many ongoing experiments CalTech, Univ. of Georgia, MPQ, etc Lens-based Or just use a (good) lens to focus light to an atom Take a Gaussian beam (laser, single-mode fiber) and do estimation E L paraxial approximation w L w f E A R P = P in 3λ πw = f 3λ πw σ L max E E A L /A Oversimplified model --- doesn t apply for strong focusing Modelling Let the field have a spherical wave front after the lens and write it in vectorial form compatible with Maxwell equations Gaussian mode Propagate field to the focus mode decomposition f parabolic wavefront: S. van Enk et al., 001, (Phys.Rev.A 63, 03809) spherical wavefront: M.K. Tey et al., 009. (NJP, 11, ) use Green theorem for a closed expression for field at focus E A determine atom response from semiclassical excitation probability for a given field 3 for weak, on-resonant excitation 0EA P 4 obtain the attering ratio R P P in Modelling results Scattering ratio for Gaussian beam 3 1, 4 1 1, : u u u e u P P R u in f w u L focusing strength 1!!! R Energy conserved!?!? w L f Interference The total field is a superposition of the excitation and attered field E Tot r E r E r in E Zumofen, et al. Phys.Rev.Lett.101, E r E A 3 e i kr kr ˆ ˆ dipolar phase lag rˆ rˆ transition E L E L The outgoing power is defined up to a constant P out E Tot P in P dr * * E r E r E r E r in assures no energy conservation violation in Projection into fiber Since no detector covers the full solid angle, we only partially collect the outgoing power natural choice --- projection onto the same mode as excitation P out g, ETot, g E E x gx k nda Integration can be carried out and we obtain experimentally measured quantities L T xs Tot g Transmission T Pout R 1 1 P Reflectivity in R R 4 R S arg1 Losses L R Near-resonant phase shift R R i i Experiment AC Stark shift Circularly polarized dipole trap defines the quantization axis and splits the degeneracy of hyperfine states F = 3 F = trapping potential The real thing.5 cm Results u = 0.9 u = 0.9 Experiment T min = 89.7 ± 0.7 % R max = 0.17 ± 0.05 % δφ max = 0.98 ± 0.07 ⁰ Theory T min = 79.6 % R max = 0.9 % δφ max =.3 ⁰ u = 0.4 Theory vs Experiment u=.4 Experiment Two reasons for direpancy: atomic motion around the focal point aberrations of the lens Temperature! MUST cool down the atom if high extinction values needed! Sideband cooling Beam geometry: Trap frequencies: 55 khz, 7 khz l Sideband cooling average motional state after cooling sequence n B-field sensitivity: ~ khz/mg 0 mg enough to shift the peak active stabilization to mg level required. Заключение Атом в сильно сфокусированном световом пучке, способен «сильно» рассеивать поле. Построена теоретическая модель, описывающая взаимодействие атома с сильно сфокусированными пучками света. За счет рамановского охлаждения, атом может быть охлажден до «почти» основного состояния ловушки Спасибо! Syed Abdullah Aljunid Meng Khoon Tey (now UIBK) Zilong Chen (now JILA) ( Harvard Florian Huber (now Brenda Chng Jianwei Lee Martin Paesold Dao Hoang Lan Teo Zhi Wei Colin ( UK Timothy Liew (now Gleb Maslennikov Valerio Scarani Christian Kurtsiefer Single atom (almost) Hanbury-Brown Twiss experiment on atomic fluoreence during cooling D 1 D photon antibunching Rabi oillation
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