Ultra low cost single chamber BEC apparatus with good optical access

王如泉Laboratory for Solid State Quantum Information Science

The Institute of PhysicsThe 4th Young Researcher Symposium on Cold Atom Physics and Q

uantum information Dalian, China

August 5th, 2010

Atomic experiments at IOPBEC of 87RbPost 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 87Rb BEC apparatus technical details

Single chamber design Home made DFB diode laser with simple frequency lock sc

heme All injection lock based laser system Second order RF modulation injection lock for repumping li

ght 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 Double MOT BEC

Single chamber BECJILA 103 pure BECStanford 104 pure BECIOP 105 pure BEC

Single chamber design vs. Double MOT design: advantages and disadvantagesSingle chamber Double MOT

Vacuum 1 chamber

1 pump

2 chambers

2 pumps

Laser cooling 6 laser beams 13 laser beams

Optical access4 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-DFB diode laser vs. external-cavity lasercavity laser

1. Great mechanical stability2. Large mode hopping free tuning range3. Very repeatable frequency tuning4. High precision temperature control (1mK)5. Less frequency cover6. Broader line width

DFB 二极管激光器 铷蒸汽室

锁相放大器

功率放大器

电流反馈

输入 参考

Master laser frequency lockMaster laser frequency lock

λ/2 λ/4

PID 控制器 输出

To experiment

Saturated spectroscopySaturated spectroscopy

780.2nm

6834.7MHz

F=3

F=2

F=1

F=0

F=2

F=1

Home made master DFB laser Home made master DFB laser

Precision temperature controller

Master laser

Magnetic field modulator

Precision current controller,Ramp generator and PID

To-3 package DFB diode with peltier cooler

Cooling laser system diagram

Master laser

Level 1 slave

80MHzAOM

Cooling laser

Repumping laser

200MHzAOM

Loading laser

200MHzAOM

80MHzAOM

3.4GHz RF Modulation

100MHzAOM

MOT Loading

Detection and optical pumping

CMOT & PGCDouble pass

To other slave lasersFor laser pumped

atomic magnetometer

Saturation spectroscopy(frequency lock

precision <1Mhz)

Repumping

Home made injection lock Home made injection lock laserslasers

Injection lock current controller

Injection lock temperature regulator

4 injection lock lasers

Master laser

Free running slave

Injected slave

频率

6.83GHz

Injection lock to the 2nd RF modulated harmonic side bandInjection lock to the 2nd RF modulated harmonic side band

dark mot: cooling -15MHz, loading -16.5normal mot: cooling -15MHz, loading -15MHzcooling power 20mW, diameter 11.4mm, total  intensity 19.6mW/cm^2 loading power 80mW, diameter 22 mm, total  intensity 21mW/cm^2 

Dark MOT

QUIC trap ：

3D magnetic field simulation Structure of the QUIC trap

0 2 4 6 8 10 12 14 160

20

40

60

80

100

120

140

160

180轴 向 磁 场

B/G

s

-10 -8 -6 -4 -2 0 2 4 6 8 100

2

4

6

8

10

12

14

16

x/mm

y/m

m

等 磁 场 强 度 线

10

10

20 20

20

20

20

30 30

30

30

30

30

40 40 40 40

40

40

40

40

4050

50

50

50

50

5050

50

50

60

60

60

60

60

60

60

60

60

70

70

70

70

70

70

70

70

80

80

80

80

80

80

80

80

90

90

90

90

90

90

90

90

100 100

100

100

100

100

100

100

110 110

110

110

110

110

110

110

120

120

120

120 120

120

120

120

130

130

130

130 130

130

130

140

140

140

140

140

150

150

150

150

150

160

160

160

160

160

170

170

170

170

180

180

180

180

190

190

190

190

200

200

200

200

210

21022

0

220

230

230

Axial magnetic field

XY plane equipotential lines 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) 167 189The University of Texas

at Austin 195 235

Timing control system

　 PC

PCI 6534

PCI 6713

RTSI

trigger

FPI 3

31 channel Digital output

8 channel Analog channel

……

……

Timing output datawith C++

System monitor with Labview

Output data fileAO, DO & Trigger

Powreful control system Bug fee operation

Imaging system

CMOT

MOT10ms

MOT

PGC Quadruple trap

Experimental results

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

Cooling parameters

Vacuum trap life

1070KHz 1060KHz 1045KHz

Pure BEC has about 1*105 atomsFinal evaporation frequency: 1070, 1060, 1045 KHz.Time of flight 20 ms.

Anisotropic BEC expansion

Anisotropic free expansion of BEC time of expansion :1ms, 5ms, 9ms, 13ms, 17ms

Future improvements: LIAD

Light induced atom desorption (LIAD) can greatly increase atom number (5×105 pure BEC expected)

C. Klempt et al.

Future improvements: transfer and Feshbach coils, ultra high resolution in situ imaging

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)

HzT /105.0 15灵敏度和最好的 SQUID 竞争，但无需液氮或液氦。

50 pT Hz–1/2 灵敏度 , 由电池供电

米粒大的超小型磁场计

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

磁场计输出信号 输出噪声能量谱

磁场测量灵敏度 50pT/√Hz

磁场计信号和灵敏度

87Rb-40K-6Li Bose Fermi MixtureMotivation•Extremely large Diopole-dipole interaction with hetero-nucleus molecules•System stability under cold collision

Ultra low collision cross section87Rb-87Rb |a|=100a0

7Li-7Li |a|=30a0

Experimental difficulties

/ 150elastic inelastic Run away condition

87Rb-40K-6Li mixture

Complicated laser system for STIRAPtwo lasers locked to a optical frequency comb

Successful group #1 DickermanEvaporation time =60s, small degenerate atom NoSuccessful group #2 R. Grimm100W dipole trap, very small degenerate atom No

Mini-trap, BEC of 7Li

Power dissipation <10W at 120ARadial field gradient 500G/cmAxial oscillation frequency 60HzTrap depth 80G

Thank you for your attention!