Ultra low cost single chamber BEC
apparatus with good optical access
王如泉
Laboratory for Solid State Quantum Information Science
The Institute of Physics
The 4th Young Researcher Symposium on Cold Atom Physics and
Quantum information
Dalian, China
August 5th, 2010
Atomic experiments at IOP
BEC of 87Rb
Post doc 王晓锐
Graduate students 罗鑫宇 高奎意
Past student 曹强
Ultra sensitive optical pumped atomic magnetometer
Graduate students 曹强
Past students 吴莎，伏吉庆，孔嘉
87Rb-40K-6Li
Bose-Fermi mixture
Post doc 张文卓
Graduate students 张峰 岳振华 刘鹏飞
Technician 赵渤
Quantum memory based on 87Rb in optical lattice
(cooperation with 吴令安）
Graduate students 裴莉亚 芦晓刚
BEC of
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BEC apparatus technical details
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87Rb
Single chamber design
Home made DFB diode laser with simple frequency lock
scheme
All injection lock based laser system
Second order RF modulation injection lock for repumping
light
Unique dark MOT scheme
Home developed real time timing control system based on
C and Labview
BEC results
Future improvements
Single chamber vs. double MOT BEC
Single chamber BEC
JILA
103 pure BEC
Stanford 104 pure BEC
IOP
105 pure BEC
Single chamber BEC
Double MOT BEC
Single chamber design vs. Double MOT
design: advantages and disadvantages
Single chamber
Double MOT
Vacuum
1 chamber
1 pump
2 chambers
2 pumps
Laser cooling
6 laser beams
13 laser beams
Optical access
4 free directions
2D optical lattice
3 free directions
1D optical lattice
No. of BEC atoms
1x105
(2～5)x105
Vacuum chamber details
DFB diode laser vs. external-cavity laser
1. Great mechanical stability
2. Large mode hopping free tuning range
3. Very repeatable frequency tuning
4. High precision temperature control (1mK)
5. Less frequency cover
6. Broader line width
Master laser frequency lock
PID控制器
锁相放大器
输出
输入
参考
功率放大器
电流反馈
λ/2
λ/4
铷蒸汽室
DFB二极管激光器
To experiment
Saturated spectroscopy
F=3
F=2
F=1
F=0
780.2nm
F=2
6834.7MHz
F=1
Home made master DFB laser
Precision temperature controller
Magnetic field modulator
Master laser
To-3 package DFB
diode with peltier cooler
Precision current controller,
Ramp generator and PID
Cooling laser system diagram
200MHz
AOM
Saturation
spectroscopy
Loading
laser
MOT Loading
(frequency lock
precision <1Mhz)
Master
laser
Level 1
slave
Detection and
optical pumping
Cooling
laser
200MHz
AOM
Repumping
laser
80MHz
AOM
80MHz
AOM
3.4GHz RF
Modulation
To other slave lasers
For laser pumped
atomic magnetometer
100MHz
AOM
Double pass
Repumping
CMOT & PGC
Home made injection lock lasers
Injection lock current controller
4 injection lock lasers
Injection lock temperature regulator
Injection lock to the 2nd RF modulated harmonic side band
Master laser
Free running slave
6.83GHz
Injected slave
频率
Dark MOT
dark mot: cooling -15MHz, loading -16.5
normal mot: cooling -15MHz, loading -15MHz
cooling power 20mW, diameter 11.4mm, total intensity 19.6mW/cm^2
loading power 80mW, diameter 22 mm, total intensity 21mW/cm^2
QUIC trap：
轴向磁场
180
160
140
120
B/Gs
100
80
60
40
20
0
3D magnetic field
simulation
Structure of the QUIC trap
0
2
4
6
8
10
12
14
16
Axial magnetic field
等磁场强度线
0
x/mm
30
20
54
70 0 0
0 10
12 0
0
80
90
11
80
90
2
14 0
16 0
17 0
15 0
4
18
19 00
20 0
21
22 00
23 0
40
90
50
60
11 0
12 0
13 0
70
10 0
-2
18
19 00
20 0
80
90
60
70
20
80
-4
14
0
17 16 0
0
20
40
30
50
40
30
90
50
60
10
70
-6
15
0
60 50
70
30
20
80
-8
60
60
50
40
30
60 50
15 0
16 0
17 0
0
-10
18 00
19
20 0
21 0 22 0
23 0
2
605040
90
40
6
4
30
112 0
111000 80
70
160 150
80
70
10 0 11 0
12 0
13 0 14 0
8
18 00
19
20 0
y/mm
90
16 0
0
15 0
17
10
0
0 110
10 102 4 0
13 1
12
70
14 0
13 0
0
112
11000
11 0 10 0
12
13 0 0
80
14
9
60 0
50
11 0 10 0
12
13 0 0
40
40
30 2
0
10
16
6
XY plane
equipotential lines
8
10
Finite element thermal simulation
Home-made QUIC trap coils
Typical QUIC trap performance
研究小组
轴向曲率Gs/cm^2 径向梯度Gs/cm
物理所
317
210
Hansch
260
225
York University
289
?
北大
260
225
武汉物理所(Ver 1)
The University of Texas
at Austin
167
189
195
235
Timing control system
31 channel
Digital output
PC
Timing output data
with C++
Output data file
AO, DO & Trigger
System monitor with
Labview
Powreful control system
Bug fee operation
……
PCI 6534
RTSI
PCI 6713
trigger
FPI 3
8 channel
Analog
……
channel
Imaging system
Experimental results
MOT
CMOT
MOT10m
s
PGC
Quadruple trap
Cooling parameters
原子数
/106
温度 /uK
密度/cm3
PSD
MOT
5*107
80
2*1010
1*10-7
CMOT
4.5*107
60
2*1011
0.5*10-6
PGC
4*107
27
0.2*1011
1*10-6
Quadruple
trap
3*107
160
2*1011
5*10-7
QUIC trap
3*107
130
1*1011
5*10-7
Vacuum trap life
1070KHz
1060KHz
Pure BEC has about 1*105 atoms
Final evaporation frequency: 1070, 1060, 1045 KHz.
Time of flight 20 ms.
1045KHz
Anisotropic BEC expansion
Anisotropic free expansion of BEC
time of expansion :1ms, 5ms, 9ms, 13ms, 17ms
Future improvements: LIAD
C. Klempt et al.
Light induced atom desorption (LIAD) can greatly increase atom number
(5×105 pure BEC expected)
Future improvements: transfer and Feshbach
coils, ultra high resolution in situ imaging
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Additional transfer coils
will be added to achieve
full 3D optical access
High spatial imaging
resolution <2μm
Feschbach resonance
coils
超高灵敏度原子磁场计
应用前景
• 反潜
• 矿产勘探（重磁法）
• 医学 (脑磁，心磁等)
• 材料的内部劳损
• 航天器的磁场导航
• 陀螺仪
美国国家标准局，原子喷泉钟
斯坦福，原子重力计
耶鲁，原子陀螺仪
三种原子干涉仪的灵敏度受
原子数的限制，并且结构非
常复杂。
原子磁场计，原子数大很多
数量级，结构简单，spin调控
成本很低。
磁场计工作原理
灵敏度极限
灵敏度最高的原子磁场计，SERF磁场计
I. K. Kominis, T. W. Kornack, J. C.
Allred & M. V. Romalis Nature 422,
596 - 599 (2003)
15
0.5 10 T / Hz
灵敏度和最好的SQUID竞
争，但无需液氮或液氦。
米粒大的超小型磁场计
50 pT Hz–1/2灵敏度, 由电池供电
物理所原子磁场计结构图
原子磁场计实验装置
Helmholtz 线圈，用于抵消地磁场。
泵浦激光和探测激光器
磁场计信号和灵敏度
磁场计输出信号
输出噪声能量谱
磁场测量灵敏度50pT/√Hz
87Rb-40K-6Li
Bose Fermi Mixture
Motivation
•Extremely large Diopole-dipole interaction with hetero-nucleus molecules
•System stability under cold collision
Experimental difficulties
Run away condition
 elastic /  inelastic  150
87Rb-40K-6Li
Ultra low collision cross section
87Rb-87Rb |a|=100a
0
7Li-7Li |a|=30a
0
Successful group #1 Dickerman
Evaporation time =60s, small degenerate atom No
Successful group #2 R. Grimm
100W dipole trap, very small degenerate atom No
Complicated laser system for STIRAP
two lasers locked to a optical frequency comb
mixture
Mini-trap, BEC of 7Li
Power dissipation <10W at 120A
Radial field gradient 500G/cm
Axial oscillation frequency 60Hz
Trap depth 80G
Thank you for your attention!