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QUEST - Centre for Quantum Engineering and Space-Time Research
1
Institut für Quantenoptik, Leibniz Universität Hannover
D. Fim, A. Kulosa, S. Rühmann, K. Zipfel, W. Ertmer and E. Rasel
A continuous loading scheme for a dipole trap
QUEST - Centre for Quantum Engineering and Space-Time Research
2Dominika Fim – RTG 1729
A magnesium frequency standard
n(24Mg: 1S0 → 3P1 )= 655 659 923 839 730 (47) Hz
Limited by the doppler effet 1st order
TT
QUEST - Centre for Quantum Engineering and Space-Time Research
3
Stability of clocks:
1st order Doppler broadening vanish improves with a higher number of
atoms
Stability of clocks:
1st order Doppler broadening vanish improves with a higher number of
atoms
A magnesium frequency standard
Dominika Fim – RTG 1729
QUEST - Centre for Quantum Engineering and Space-Time Research
4
• Optical cooling of magnesium– Stepwise loading scheme of dipole traps
• L im ita tions
– 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
Outline
Dominika Fim – RTG 1729
QUEST - Centre for Quantum Engineering and Space-Time Research
5
Optical cooling of magnesiumSinglet Triplet
(3s2) 1S0
(3s3p) 1P1
012
(3s3p) 3P
231
(3s3d) 3D
383 nm26 MHz
457 nm36 Hz
285 nm78 MHz
5
Singlet-MOT: 3 mKSinglet-MOT: 3 mK Interkombination transition:low photon scattering rate
Singlet-MOT: 3 mK intercombination transition:low photon scattering rate
Triplet-MOT: 1 mKdensity limitation!
Light at the magic wavelength ionize atoms from 3D states
469 nm
Dominika Fim – RTG 1729
QUEST - Centre for Quantum Engineering and Space-Time Research
6
Singlet Triplet
(3s2) 1S0
(3s3p) 1P1
012
(3s3p) 3P
231
(3s3d) 3D
285 nm78 MHz
Singlet-MOT:Number of atoms: 3 10∙ 9 Temperature: 3mK
S-MOT
Decay of the number of atoms:
R - loading rate = 5 10∙ 8 1/sα - one-body lossesƮ = 1/α 17s �Limitation: one-body loss
Dominika Fim – RTG 1729
QUEST - Centre for Quantum Engineering and Space-Time Research
7
T-MOT
Singlet Triplet
(3s2) 1S0
(3s3p) 1P1
012
(3s3p) 3P
231
(3s3d) 3D
383 nm26 MHz
457 nm36 Hz
285 nm78 MHz
Triplet-MOT:Number of atoms: 10 � 8 Temperature: 1mK
Decay of the number of atoms:
α - one-body lossesβ - two-body lossesƮ = 1/α � 1 s (decay: 3P1 → 1S0 )Two-body loss at high number of atoms
Trap time tdec / s
Num
ber o
f ato
ms:
T-M
OT
Sequential loading scheme:
Atoms in the dipole trap: 3P2 state limited by binary collisions and density
Dominika Fim – RTG 1729
QUEST - Centre for Quantum Engineering and Space-Time Research
8
Continuous- loading scheme
Singlet Triplet
(3s2) 1S0
(3s3p) 1P1
012
(3s3p) 3P
231
(3s3d) 3D
383 nm26 MHz
457 nm36 Hz
285 nm78 MHz
Dominika Fim – RTG 1729
QUEST - Centre for Quantum Engineering and Space-Time Research
9
Comparison of the loading schemes
• Loading rates are equal: 1.2∙ 103 1/s • Continuous loading: limited by lifetime Ʈ = 4.5 s• Sequential: saturation at Ʈ = 1.1 s
• 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
Atom
zahl
Lifetime of the dipole trap
loading time / s
continuous τ=4,5 s
sequential τ=1,1 s
Atom
zahl
loading: dipole trap
Nu
mb
er o
f at
oms
N
Nu
mb
er o
f at
oms
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
W0= 11 mmW0= 3.1 mm
Saturation on 3P2 → 3D3
Num
ber o
f ato
ms
in th
e di
pole
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
0 2 4 6 8 10 12 14 16102
103
104
105Decay
num
ber
of a
tom
s in
the
dip
ole
trap
time / s
Dominika Fim – RTG 1729
QUEST - Centre for Quantum Engineering and Space-Time Research
12
3P0 + 3P0
1S0 + 3P0
2,7 eVEner
gie
3P0 + 3P0
1S0 + 3P0
0,024 eV
(3s2)1S0 + (3s4s)1S0
2,7 eVEner
gie
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
Singulett Triplett
(3s2) 1S0
(3s3p) 1P1
012
(3s3p) 3P
231
(3s3d) 3D(3s4s) 1S0
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!!
Number of atoms:Stepwise: 1.1 10∙ 3 Continuous: 4.5 10∙ 3 Optimized continuous: 3 10∙ 5
Loading rate:Stepwise/Continuous: 1.2 103 1/sOptimized continuous: 1.3 105 1/s
Dominika Fim – RTG 1729
QUEST - Centre for Quantum Engineering and Space-Time Research
14
...we were able to trap magnesium atoms in an optical lattice
...we were able to trap magnesium atoms in an optical lattice
Singulett Triplett
(3s2) 1S0
(3s3p) 1P1
012
(3s3p) 3P
231
(3s3d) 3D
383 nm26 MHz
457 nm36 Hz
285 nm78 MHz
10.000 Atome in 3 s !!
…due to the continuous loading scheme
Dominika Fim – RTG 1729
QUEST - Centre for Quantum Engineering and Space-Time Research
1525.03.2010 15
• Presented a continuous loading scheme for 3P0 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
• Presented a continuous loading scheme for 3P0 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