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 $ Funding $ NIST, NASA, ONR, NSF, AFOSR, DOE NASA Fundamental Physics Research in Space Airlie, May 23, 2006

Exciting time for light control Continuous wave laser: < 1 Hz stability and accuracy Ultrafast pulse: < 1 fs generation and control Figure of merit: Phase coherence after optical cycles

ICOLS 2005 Hawaii,2001 Learn from Giants Hall and Hänsch: Nobel Prize 2005

Frequency comb: state-of-the-art n = n f r  – f o Optical Synthesizer I( ) frfr f0f0 1/ f r =   o  +  oo Waveform control f r uniformity < Absolute inaccuracy < Short term instabilities ~ 10 1s Comb linewidth ~ 0.3 Hz  < rad, timing jitter < 1 fs Ye & Cundiff, Eds., “Comb” book, Springer (2005). Udem, Holzworth, & Hänsch, Nature 416, 233 (2002). Visible Frequency (Hz) Freq. comb 10 6 :1 Reduction Gear

Comparison of Hz-linewidth lasers across the visible spectrum Laser nm Cavity 2 Laser nm Cavity 1 Laser 1 Laser 2 Femto comb 30 m noise-cancelled fiber 35 m noise-cancelled fiber Ludlow et al., PRL 96, (2006). Beat width: 3 Hz 20 Hz 5 Hz 4/11/ 2006

Oscillator Counter  a Atoms New era for optical atomic clocks Diddams et al., Science 293, 825 (2001). Ye et al, Phys. Rev. Lett. 87, (2001). Feedback (accuracy) Ultrastable laser optical comb optical frequency synthesizer & counter RF or optical readout

T ~ 0.5 photon recoil ~ 220 nK Cool Alkaline Earth – Strontium 689 nm 1S01S0 3P23P2 3P13P1 3P03P0 698 nm 88 Sr 1 S P kHz7x < 10mHz~ Sr 1 S P 0 δ / at 1s Γ/2π 00 00 Xu et al., Phys. Rev. Lett. 90, (2003). Loftus et al., Phys. Rev. Lett. 93, (2004). Ido et al., Phys. Rev. Lett. 94, (2005). Santra et al., Phys. Rev. Lett. 94, (2005). Ludlow et al., Phys. Rev. Lett. 96, (2006). Zelevinsky et al., Phys. Rev. Lett. 96, (2006).

Spectroscopy at the magic wavelength 1S01S0 3P03P0 1-D Lamb-Dicke Regime η = kx 0 = (  recoil /  z ) 0.5 ~ 0.23  trap Red sideband Blue SB Carrier

1S01S0 3P03P0 Optical probe AC Stark shift of the lattice potential at magic

Absolute Frequency of 87 Sr 1 S 0 – 3 P 0 March 2, 2006 FWHM 15 Hz Ludlow et al., Phys. Rev. Lett. 96, (2006). Accuracy soon reaching 1 x April, 2006 Q ~ 1 x Projected stability < 1 x at 1 s

Ultracold molecules via Photoassociation * 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 (5s 2 ) 1 S nm,  = 7.6 kHz 3P13P1 (5s5p)

Observed Molecular Lines Dips correspond to trap loss when the PA laser is resonant to make excited Sr 2 molecules Zelevinsky et al., Phys. Rev. Lett. 96, (2006).

Cold molecules to test time-variation of electron/proton mass ratio Pump Probe Vibration ~ m e /m p Electronic ~  Sr 2 pump probe  ( pump – probe ) < 0.5 Hz

Cold OH molecules to constrain  Hyperfine interactions  ~  4 Lambda doubling  ~   3/2 F’= 2 F’= 1 F= 2 F= 1 Multiple transitions from the same gas cloud (different dependences on  ) (Self check on systematics) Current uncertainly in laboratory based experiments is 100 Hz, leading to  ~ ter Meulen & Dymanus, Astrophys. J. 172, L21(1972). OH megamasers High redshift z > 1 Darling, Phys. Rev. Lett 91, (2003). Chengalur et al., Phys. Rev. Lett. 91, (2003). Kanekar et al., Phys. Rev. Lett. 93, (2004).

p F net v Stark deceleration Second step: slow the molecules in to the rest frame of the lab + - p v Energy Position Conservative process, no cooling Phase space selection Phase space area linked to the deceleration angle (  0 ) Phase space rotation (constant density) Resembles a pendulum driven by a constant torque

Cold molecule based precision spectroscopy PMT Excitation laser Microwave Interrogation cavity Hexapole Decelerator Rabi or Ramsey interrogation on slowed OH beam High resolution and precision Systematic checks on beam (velocity) effects Detection can

Transition lineshape and center 1 kHz Rabi lineshape Highest resolution spectral feature (OH) Transition frequency determined < 5 Hz (20 x improvement) 200 m/s beam

Long term averaging Weighted standard mean error range Hudson et al., Phys. Rev. Lett. 96, (2006).

 /  measurement status  /  = 1 ppm (and better) is now possible to measure over ~10 Gyr. Linear drift model → /yr. 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. e-

Special thanks 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) Femtosecond comb & cold atoms S. Foreman M. Thorpe M. Stowe D. Hudson Dr. R. J. Jones Dr. K. Moll Dr. A. Peer Ultracold Sr M. Boyd A. Ludlow S. Blatt Dr. T. Zelevinsky Dr. T. Ido Dr. T. Zanon Cold Molecules E. Hudson B. Sawyer Dr. B. Lev