QUEST - Centre for Quantum Engineering and Space-Time Research 1 A continuous loading scheme for a dipole trap

QUEST - Centre for Quantum Engineering and Space-Time Research 2 Low sensitivity to blackbody radiation Bosonic and fermionic isotopes available Low sensitivity to blackbody radiation Bosonic and fermionic isotopes available Dominika Fim – RTG 1729 A magnesium frequency standard ( 24 Mg: 1 S 0 → 3 P 1 )= (47) Hz  Limited by the doppler effet 1 st order T T

QUEST - Centre for Quantum Engineering and Space-Time Research Stability of clocks:  1 st order Doppler broadening vanish  improves with a higher number of atoms Stability of clocks:  1 st order Doppler broadening vanish  improves with a higher number of atoms 3 A magnesium frequency standard Dominika Fim – RTG 1729

QUEST - Centre for Quantum Engineering and Space-Time Research Optical cooling of magnesium –Stepwise loading scheme of dipole traps Limitations –Continuous loading scheme of dipole traps Comparison of the loading schemes Improvements Conclusion Optical cooling of magnesium –Stepwise loading scheme of dipole traps Limitations –Continuous loading scheme of dipole traps Comparison of the loading schemes Improvements Conclusion 4 Outline Dominika Fim – RTG 1729

QUEST - Centre for Quantum Engineering and Space-Time Research 5 Optical cooling of magnesium SingletTriplet (3s 2 ) 1 S 0 (3s3p) 1 P (3s3p) 3 P (3s3d) 3 D 383 nm 26 MHz 457 nm 36 Hz 285 nm 78 MHz 5 Singlet-MOT: 3 mK Interkombination transition: low photon scattering rate Singlet-MOT: 3 mK intercombination transition: low photon scattering rate Triplet-MOT: 1 mK density limitation! Light at the magic wavelength ionize atoms from 3 D states 469 nm Dominika Fim – RTG 1729

QUEST - Centre for Quantum Engineering and Space-Time Research 6 SingletTriplet (3s 2 ) 1 S 0 (3s3p) 1 P (3s3p) 3 P (3s3d) 3 D 285 nm 78 MHz Singlet-MOT: Number of atoms: 3 ∙ 10 9 Temperature: 3mK S-MOT Decay of the number of atoms: R - loading rate = 5 ∙ /s α - one-body losses Ʈ = 1/α ̴ 17s Limitation: one-body loss Dominika Fim – RTG 1729

QUEST - Centre for Quantum Engineering and Space-Time Research 7 T-MOT SingletTriplet (3s 2 ) 1 S 0 (3s3p) 1 P (3s3p) 3 P (3s3d) 3 D 383 nm 26 MHz 457 nm 36 Hz 285 nm 78 MHz Triplet-MOT: Number of atoms: ̴ 10 8 Temperature: 1mK Decay of the number of atoms: α - one-body losses β - two-body losses Ʈ = 1/α ̴ 1 s (decay: 3 P 1 → 1 S 0 ) Two-body loss at high number of atoms Trap time t dec / s Number of atoms: T-MOT Sequential loading scheme: Atoms in the dipole trap: 3 P 2 state limited by binary collisions and density Dominika Fim – RTG 1729

QUEST - Centre for Quantum Engineering and Space-Time Research Continuous- loading scheme 8 Singlet Triplet (3s 2 ) 1 S 0 (3s3p) 1 P (3s3p) 3 P (3s3d) 3 D 383 nm 26 MHz 457 nm 36 Hz 285 nm 78 MHz Dominika Fim – RTG 1729

QUEST - Centre for Quantum Engineering and Space-Time Research 9 S-MOT T-MOT - 3 P 0 repumper 1064 nm Dipole trap 285 nm  79 MHz 457 nm  36 Hz 383 nm  26 MHz LoadingDetection 3 s10 ms1 - 8 s20 ms S-MOT 1 S 0 → 1 P 1 Tarnsfer 1 S 0 → 3 P 1 Rp- P 1 3 P 1 → 3 D 2 T-MOT 3 P 2 → 3 D 3 Rp. P 0 3 P 0 → 3 D 1 dipole trap B - field Comparison of the loading schemes Loading rates are equal: 1.2∙10 3 1/s Continuous loading: limited by lifetime Ʈ = 4.5 s Sequential: saturation at Ʈ = 1.1 s capture time / s Atomzahl Lifetime of the dipole trap loading time / s continuous τ =4,5 s sequential τ =1,1 s Atomzahl loading: dipole trap Number of atoms N Dominika Fim – RTG 1729

QUEST - Centre for Quantum Engineering and Space-Time Research 10 spatial expansion of the T-MOT (limited by temperature) → low detuning → high intensity → Density limitation: high photon scattering rate (reabsorption, inelastic collisions) → Optimization only for the continuous loading scheme Enhancement of the loading rate W 0 = 11 mm W 0 = 3.1 mm Saturation on 3 P 2 → 3 D 3 Number of atoms in the dipole trap Higher loadingefficiency due to higher Intensity Dominika Fim – RTG 1729

QUEST - Centre for Quantum Engineering and Space-Time Research 11 small number of atoms: exponential decay high number of atoms: loss attributed to binary collisions Raise of Temperature → elastic collisions rather unlikely → inelastische collisions Decay curve Dominika Fim – RTG 1729

QUEST - Centre for Quantum Engineering and Space-Time Research 3 P P 0 1 S P 0 2,7 eV Energie 3 P P 0 1 S P 0 0,024 eV (3s 2 ) 1 S 0 + (3s4s) 1 S 0 2,7 eV Energie 12 Due to the collision both atoms change their atomic state → for the low energy difference collision at high distances possible Ʈ = 1/α = 4.2 s A high energy difference requires a low distance → rather unlikely SingulettTriplett (3s 2 ) 1 S 0 (3s3p) 1 P (3s3p) 3 P (3s3d) 3 D (3s4s) 1 S 0 Inelastic collisions Dominika Fim – RTG 1729

QUEST - Centre for Quantum Engineering and Space-Time Research 13 Results -> the dipole trap loading rate was increased by two orders of magnitude: 3 ∙ 10 5 atoms in the trap!! Dominika Fim – RTG 1729

QUEST - Centre for Quantum Engineering and Space-Time Research...we were able to trap magnesium atoms in an optical lattice 14 Singulett Triplett (3s 2 ) 1 S 0 (3s3p) 1 P (3s3p) 3 P (3s3d) 3 D 383 nm 26 MHz 457 nm 36 Hz 285 nm 78 MHz Atome in 3 s !! …due to the continuous loading scheme Dominika Fim – RTG 1729

QUEST - Centre for Quantum Engineering and Space-Time Research Presented a continuous loading scheme for 3 P 0 which avoids density limitation by introducing additional loss channel to T-MOT increased loading rate dipole trap by two orders of magnitude Number of atoms in the dipole trap is limited by two-body loss collisions Conclusion Dominika Fim – RTG 1729

QUEST - Centre for Quantum Engineering and Space-Time Research 16 Prof. Dr. Wolfgang Ertmer Prof. Dr. Ernst M. Rasel Group leader… Dominika Fim – RTG 1729

QUEST - Centre for Quantum Engineering and Space-Time Research 17 …and the magnesium Team