Formation, trapping and collisions with ultra-cold molecules

Formation, trapping and collisions with ultra-cold molecules

Atomes de Rydberg (4 corps)
&
Molécules froides (pompage optique)
Daniel Comparat
Laboratoire Aimé Cotton
Orsay
France
Experiments in the « Cold atoms and molecules group »
Cesium Magneto-Optical Trap
(P. Pillet, H. Lignier, D. Comparat)
-Cold cesium molecules (formation, vibrational cooling, trapping, ..)
Cs,Ytterbium MOT: (D. Comparat, P. Cheinet, P.Pillet)
-Cold Rydberg atoms (dipole blockade, plasma ….)
Stark & Zeeman (mol.) decelerators (P. Pillet, J. Robert,
N. Vanhaecke)
Production of ion and electron sources from cold atoms
(P. Pillet, A. Fioretti, D. Comparat)
Experiment LAC
(mol/Ryd)
 Ridha Horchani
 Paul Huillery
 Issam Manai
 Joshua Gurian
 Andréa Fioretti
 Daniel Comparat
 Hans Lignier
 Patrick Cheinet
 Pierre Pillet
Collaboration
 Béatrice Chatel
 Sébastien Weber
LCAR, Toulouse
 Antoine Browaeys
 Philippe Grangier
LCFIO, Palaiseau
AEGIS, Orsay Physics, …
Visitors
 Maria Allegrini
 Emiliya Dimova
 Lirong Wang
 Jianming Zhao
 Phil Gould
 Nikolai Vitanov
Theory LAC
 Nadia Bouloufa
 Olivier Dulieu
Cold Rydberg gaz (exp + th):
R = n2 a0 ~ 1µm
Cs+
e-
dipole µ ~ n2 ea0 ~ 10000 D
1998: Many body in Frozen gaz (1/R3)
2000: Motion  collisions  plasma
Exotic Molecules
2001: Gate using dipole blockade
2004: VdW (1/R6) blockade
2006: Dipole (1/R3) blockade.
2007: Coherent excitation (Rabi, EIT, …)
2008: Trapping
2009: 2 atoms blockade, trapping
2010: 2 atoms gate, quantum simulator
2011: few body ?
LPL (oct2008)
J. Opt. Soc. Am. B 27, A208 (2010)
Dipole-dipole  µµ‘/R3
Rydberg
10 MHz dipole-dipole
1
0
1
A
4
B 0
1998 Förster resonance energy transfer
23p3/2 + 23p3/2 → 23s + 24s
d
s
p
p‘
s‘
2 body 80.0
LPL (oct2008)
Cs: 2 Enp(F0 ) = Ens (F0) + E(n+1)s (F0)
1998-2010: 2 body resonance
24s + 24 s → +23p1/2+23d5/2
d
s
p
p‘
s‘
2 body
LPL (oct2008)
80.5
2011: 4 body resonance
23p3/2 + 23p3/2 + 23p3/2 + 23p3/2 → 23s + 23s +23p1/2+23d5/2
d
s
p
p‘
s‘
4 body 80.1
Vdd
LPL (oct2008)
Conclusion
•Observation of direct product of Stark-tuned 4-body interaction
•Density scaling ~ n4
•On-res. 4-body process > Off-res. 2-body process
•Next:
•Further control multibody Rydberg interaction via RF or B-field.
•Quantum control of few atoms: Landau-Zener transitions
• Rydberg and ion/electron imaging experiments
• Two-electrons Rydberg (Yb):
one Rydberg electron, another to image, manipulate
LPL (oct2008)
Cold Molecules: Why?
Quantum information, computation, logic (dipole cf Rydberg)…
Precise measurement
Improved measurement of the
shape of the electron
Nature 473, 493 (26 May 2011)
Fundamental test (e- dipole, chirality, constant variation)
Quantum properties (dipole), BEC,BCS
Control of (Reactive) collisions: quantum chemistry
Photochemistry (photoassociation)
Superchemistry (Feshbach, …)
Need ultra-cold molecules (T~0K) and in v=J=0
Formation of cold molecules:
Ex: photoassociation from atoms
Translation
cold
+
Several Vibration
(Hot, not v=0)
GOAL
Translation
cold
+
Vibration
cold
Population after PA
Several vibrational level of
triplet state no singlet
decay PA
Triplet-singlet conversion
Scheme for state conversion of MANY levels!
Broadband femtosecond laser + decay
Population after conversion
Several vibrational levels
singlet no triplet
Conversion
~ 80% efficient
Transfering several levels (PA)
• Broadband laser
– Excite « all » levels towards an excited state (B)
9600
1
B u
9500
-1
Energy (cm )
9400
9300
1
9200
-3200
-3300
-3400
-3500
1 +
X g
-3600
8
9
R (A0)
10
Intensité
Optical pumping and vibrational cooling
140
120
100
80
60
40
20
0
12800
12900
13000
-1
nombre d'onde (cm )
13100
Optical pumping and vibrational cooling
• Spontaneous emission:
– Redistribution of population in ground state X
9600
1
B u
9500
-1
Energy (cm )
9400
9300
1
9200
2
-3200
-3300
-3400
-3500
1 +
X g
-3600
8
v=0
9
R (A0)
10
8
9
R (A0)
10
Intensité
Optical pumping and vibrational cooling
• Repetition
140
120
100
80
60
40
20
0
12800
12900
13000
-1
nombre d'onde (cm )
9600
1
B u
9500
9300
-1
Energy (cm )
9400
1
9200
2
3
-3200
-3300
-3400
-3500
1 +
X g
-3600
8
v=0
9
R (A0)
10
8
9
R (A0)
v=0
10
8
9
R (A0)
10
13100
Intensité
Optical pumping and vibrational cooling
• Shaping of the laser:
– No absorption from v=0 level
→ dark state
9600
140
120
100
80
60
40
20
0
12800
12900
1
B u
9500
-1
Energy (cm )
9400
9300
1
9200
2
3
-3200
-3300
-3400
-3500
1 +
X g
-3600
8
v=0
9
R (A0)
10
8
13000
-1
nombre d'onde (cm )
9
R (A0)
v=0
10
8
9
R (A0)
10
13100
Intensité
Optical pumping and vibrational cooling
– Accumulation in dark
140
120
100
80
60
40
20
0
12800
state v=0
12900
13000
-1
13100
nombre d'onde (cm )
→ cooling of the vibration
9600
1
B u
9500
-1
Energy (cm )
9400
9300
1
9200
2
3
i
-3200
-3300
-3400
-3500
1 +
X g
-3600
8
v=0
9
R (A0)
10
8
9
R (A0)
v=0
v=0
10
8
9
R (A0)
10
8
9
R (A0)
10
Population after pumping
Single vibrational level
of singlet state no triplet
pumping
~ 40% efficient
Better than optimal
Single transfert (STIRAP)
Limited by laser linewidth
Conclusion
- Manipulation of the vibration
(better than STIRAP)
NEXT:
Improve efficiency near 100%
Extend the work to the rotation
Toward laser cooling of molecules !
Repeat !