Transcript Ye - UCLA Physics & Astronomy

Precision measurement with
ultracold atoms and molecules
Jun Ye
JILA, National Institute of Standards and Technology and
Department of Physics, University of Colorado at Boulder
http://jilawww.colorado.edu/YeLabs
NASA Fundamental Physics Research in Space
Airlie, May 23, 2006
$ Funding $
NIST, NASA,
ONR, NSF,
AFOSR, DOE
Exciting time for light control
Continuous wave laser: < 1 Hz stability and accuracy
Ultrafast pulse:
< 1 fs generation and control
Figure of merit: 10-15
Phase coherence after 1015 optical cycles
Learn from Giants
Hawaii,2001
ICOLS 2005
Hall and Hänsch: Nobel Prize 2005
Frequency comb: state-of-the-art
Freq. comb
Reduction Gear
• Optical Synthesizer
106 :1
Visible
n n= n f r – f o
I(n)
fr
n
f0
1011
1012
1013
1014
1015
Frequency (Hz)
• fr uniformity < 10-18
• Waveform control
fo +Df
fo
1010
• Absolute inaccuracy < 10-15
• Short term instabilities ~ 10-15 @ 1s
• Comb linewidth ~ 0.3 Hz
• Df < 10-2 rad, timing jitter < 1 fs
1/ fr = t
Ye & Cundiff, Eds., “Comb” book, Springer (2005).
Udem, Holzworth, & Hänsch, Nature 416, 233 (2002).
Comparison of Hz-linewidth lasers across the visible spectrum
Linear Scale
3.0
4/11/ 2006
Optical
linewidth:
Beat
width:
35Hz
Hz
2.0
252 mHz
1.0
Ludlow et al., PRL 96, 033003(2006).
20 Hz
Laser 2 Cavity 2
1064 nm
0.0
55
60
Laser 2
65
70
75 Hz
Laser 1
n
Femto comb
Laser 1 Cavity 1
700 nm
New era for optical atomic clocks
Diddams et al., Science 293, 825 (2001).
Ye et al, Phys. Rev. Lett. 87, 270801 (2001).
Oscillator
Dn
Feedback
(accuracy)
na
Atoms
Ultrastable laser
Counter
optical frequency
synthesizer & counter
optical comb
RF or optical
readout
Cool Alkaline Earth – Strontium
Xu et al.,
Phys. Rev. Lett. 90, 193002 (2003).
Loftus et al., Phys. Rev. Lett. 93, 073003 (2004).
Ido et al.,
Phys. Rev. Lett. 94, 153001 (2005).
Santra et al., Phys. Rev. Lett. 94, 173002 (2005).
Ludlow et al., Phys. Rev. Lett. 96, 033003 (2006).
Zelevinsky et al., Phys. Rev. Lett. 96, 203201 (2006).
88Sr 1S -3P
0
1
87Sr 1S -3P
0
0
Γ/2π
δn/n at 1s
7.6 kHz
7x10-16
T ~ 0.5 photon recoil
~ 220 nK
3P
2
3P
1
< 10mHz ~10-18
3P
0
689 nm
698 nm
1S
0
w0
w0
Spectroscopy at the magic wavelength
1-D Lamb-Dicke Regime
η = kx0 = (wrecoil / wz )0.5 ~ 0.23
3P
0
3500
1S
0
wrecoil  wtrap
clock  wtrap
Photon counts
wtrap
3000
2500
2000
Red sideband
1500
wtrap
1000
Blue SB
Carrier
500
-60
-40
-20
0
20
40
Optical frequency (Hz)
60
AC Stark shift of the lattice potential at magic
3P
0
Optical
probe
nsr - 429228004229900 [Hz]
1S
0
10
0
Lattice Stark shift
@ magic: 0(3) Hz/I0
-10
-20
-30
0.6
0.8
1.0
Lattice Intensity [I/I0]
1.2
Absolute Frequency of
2800
1.05
Q ~ 1 x 1014
87Sr
1S
0
– 3P0
Ludlow et al., Phys. Rev. Lett. 96, 033003 (2006).
3200
1.00
3000
2400
Accuracy soon reaching
1 x 10-15
0.95
2600
2000
2400
0.90
2200
FWHM
15 Hz
FWHM:
4.6 Hz
2000
Linewidth:
1600
0.85
1800
1600
1400
0.80
1200
200 (30) Hz
April, 2006
1200
nsr - 429228004229900 [Hz]
Photon
counts
PhotonCounts
counts
Photon
2800
-20 March
-10
0 2006
10
20
30
2,
0.75-0.9 -0.6 -0.3 0.0 0.3 0.6
Clock Laser Detuning (Hz)
-300 -200
-100 0 (kHz)
100
698 nm probe
frequency
Frequency scan (Hz)
Projected stability
< 1 x 10-15 at 1 s
60
JILA 2005
40
20 -17.6 ± 2.8 (stat) ± 20 (sys) Hz
0
-20
-40
-60
-80
2006
2005
-100
5/3
5/31
6/28
2/10 3/10
Date (2005 - 2006)
Ultracold molecules via Photoassociation
3P
1
(5s2) 1S0
* Narrow linewidth resolves the last few bound states →
Determination of long-range potentials and atomic properties
* Dipole – dipole interaction similar to Van der Waals
* Optically control cold collisions with low atom loss
(5s5p)
Observed Molecular Lines
Dips correspond to trap loss when the PA laser is resonant
to make excited Sr2 molecules Zelevinsky et al., Phys. Rev. Lett. 96, 203201 (2006).
Cold molecules to test time-variation
of electron/proton mass ratio
Electronic
~ a
Probe
Pump
npump
nprobe
Sr2
Vibration
~ me/mp
n
d(npump – nprobe) < 0.5 Hz
Cold OH molecules to constrain a
F’= 2
Hyperfine
4
interactions
~
a
F’= 1
2P
3/2
OH megamasers
Lambda doubling ~ a 0.4
High redshift z > 1
F= 2
F= 1
Darling, Phys. Rev. Lett 91, 011301 (2003).
Chengalur et al., Phys. Rev. Lett. 91, 241302 (2003).
Kanekar et al., Phys. Rev. Lett. 93, 051302 (2004).
Multiple transitions from the same gas cloud (different dependences on a)
(Self check on systematics)
Current uncertainly in laboratory based experiments is 100 Hz,
leading to Da/a ~ 10-5
ter Meulen & Dymanus, Astrophys. J. 172, L21(1972).
Stark deceleration
Second step: slow the molecules in to the rest frame of the lab
+
v
p
+
-
v
p
+
Phase space selection
-
Phase space area linked to the
deceleration angle (f0)
-
Phase space rotation
(constant density)
Resembles a pendulum driven
by a constant torque
Energy
Fnet
Conservative process, no cooling
Position
Cold molecule based precision spectroscopy
• Rabi or Ramsey interrogation on slowed OH beam
• High resolution and precision
• Systematic checks on beam (velocity) effects
PMT
Decelerator
Hexapole
Detection can
Excitation laser
Microwave
Interrogation cavity
Transition lineshape and center
F = 2'  F = 2 Transition
F' = 2 Population
1.0
Rabi lineshape
0.9
Highest resolution
spectral feature (OH)
0.8
0.7
200 m/s
beam
1 kHz
0.6
0.5
0.4
Transition frequency
determined < 5 Hz
(20 x improvement)
fcenter = -37.9 ± 11.3 Hz
-4000 -3000 -2000 -1000
0
1000 2000 3000 4000
f - 1667359030 [Hz]
Long term averaging
Hudson et al., Phys. Rev. Lett. 96, 143004 (2006).
Weighted
standard mean
error range
Da/a measurement status
Da / a = 1 ppm (and better) is now
possible to measure over ~10 Gyr.
Linear drift model → 10-16/yr.
e-
e-
e-
e-
Astrophysical measurements later
this year plan better than 100 Hz
accuracy.
Deep surveys of OH megamasers are
active from the local Universe to red
shift z ~ 4.
Optical clock comparisons ongoing,
but test only modern epoch.
Special thanks
http://jilawww.colorado.edu/YeLabs
Cold Molecules
Ultracold Sr
E. Hudson
B. Sawyer
Dr. B. Lev
M. Boyd
A. Ludlow
S. Blatt
Dr. T. Zelevinsky
Dr. T. Ido
Dr. T. Zanon
Femtosecond comb
& cold atoms
S. Foreman
M. Thorpe
M. Stowe
D. Hudson
Dr. R. J. Jones
Dr. K. Moll
Dr. A. Peer
Collaborators
M. Notcutt, J. L. Hall, J. Bohn, S. Cundiff, C. Greene (JILA)
P. Julienne, S. Diddams, J. Bergquist, L. Hollberg, T. Parker (NIST)
C. Taatjes (Sandia), E. Arimondo (Pisa)