No abstract

No abstract

With ultracold 88Sr in a 1D magic wavelength optical lattice, we performed narrow-line photoassociation spectroscopy near the 1S0 - 3P1 intercombination transition. Nine least-bound vibrational molecular levels associated with the long-range 0u and 1u potential energy surfaces were measured and identified. A simple theoretical model accurately describes the level positions and treats the effects of the lattice confinement on the line shapes. The measured resonance strengths show that optical tuning of the ground state scattering length should be possible without significant atom loss.

Highest resolution laser spectroscopy has generally been limited to single trapped ion systems due to rapid decoherence which plagues neutral atom ensembles. Here, precision spectroscopy of ultracold neutral atoms confined in a trapping potential shows superior optical coherence without any deleterious effects from motional degrees of freedom, revealing optical resonance linewidths at the hertz level with an excellent signal to noise ratio. The resonance quality factor of 2.4 x 10 14 is the highest ever recovered in any form of coherent spectroscopy. The spectral resolution permits direct observation of the breaking of nuclear spin degeneracy for the 1 S 0 and 3 P 0 optical clock states of 87 Sr under a small magnetic bias field. This optical NMR-like approach allows an accurate measurement of the differential Landé g-factor between the two states. The optical atomic coherence demonstrated for collective excitation of a large number of atoms will have a strong impact on quantum measurement and precision frequency metrology.

We have demonstrated a recoil-free spectroscopy on the 1 S0 − 3 P1 transition of strontium atoms confined in a one-dimensional optical lattice. By investigating the wavelength and polarization dependence of the ac Stark shift acting on the 1 S0 and 3 P1(mJ = 0) states, we determined the magic wavelength where the Stark shifts for both states coincide. The Lamb-Dicke confinement provided by this Stark-free optical lattice enabled the measurement of the atomic spectrum free from Doppler as well as recoil shifts.PACS numbers: 32.80. Pj, 32.30.Jc, 32.60.+i, 32.70.Jz Recent dramatic advances in optical metrology have made it possible to directly link two optical frequencies with an uncertainty below 10 −18 [1] and to coherently divide an optical frequency down to a radio frequency defined by the SI second [2]. Owing to these techniques, a stringent comparison of the stability and accuracy among optical clocks becomes feasible [3] and leads to an improved definition of time and a test of the time variation of a fundamental constant [4]. Up to now, two sorts of absorbers, single ions in the Lamb-Dicke regime (LDR) [5] and neutral atoms in free space, have been extensively studied for optical clocks. Tightly confined single ions, enabling a long interaction time and the Doppler-as well as the recoil-free absorption [6], have, so far, led to the narrowest optical spectrum [7]. However, the stability was severely limited by the quantum projection noise (QPN) [8] of the single absorber. The ensemble of neutral atoms, in contrast, provides a far better QPN limit. The accuracy of the measurement is known to be affected by the atomic motion, as residual Doppler shifts are introduced through the imperfect wave front of the probe beam [9,10].These two approaches could merge if an ensemble of neutral atoms were separately prepared in the LDR. An optical lattice made by the interference pattern of a light field [11] confines atoms in a small volume, which satisfies the Lamb-Dicke condition [5]. However, an impediment for the precision measurement is the complete control over the perturbations caused by this container, since the Stark shift potential strongly depends on the electronic state, which is not the case for ion-trapping potential.The transition frequency between the states, |g and |e , subjected to the ac Stark shift of the trap laser with * Current address: JILA, University of Colorado, CO 80309-0440.† Author to whom correspondence should be addressed. E-mail address: katori@amo.t.u-tokyo.ac.jp an electric field of E(ω L ,ǫ), can be written as,Here, ω e −ω g (= ω 0 ) is the unperturbed atomic resonance frequency, anddenotes the differential dipole-polarizability. If the polarizabilities α e and α g coincide at a specific trapping laser frequency ω L and polarizationǫ, the second term of Eq. (1) vanishes. Therefore, the unperturbed atomic transition frequency, independent of the trapping laser intensity of I L ∝ | E| 2 , can be observed [12,13]. This Stark shift cancellation technique was first demonstrated by an impr...

With ultracold 87Srconfined in a magic wavelength optical lattice, we present the most precise study (2.8 Hz statistical uncertainty) to date of the 1S0-3P0 optical clock transition with a detailed analysis of systematic shifts (19 Hz uncertainty) in the absolute frequency measurement of 429 228 004 229 869 Hz. The high resolution permits an investigation of the optical lattice motional sideband structure. The local oscillator for this optical atomic clock is a stable diode laser with its hertz-level linewidth characterized by an octave-spanning femtosecond frequency comb.

Aided by ultrahigh resolution spectroscopy, the overall systematic uncertainty of the 1S0-3P0 clock resonance for lattice-confined 87Sr has been characterized to 9 x 10(-16). This uncertainty is at a level similar to the Cs-fountain primary standard, while the potential stability for the lattice clocks exceeds that of Cs. The absolute frequency of the clock transition has been measured to be 429 228 004 229 874.0(1.1) Hz, where the 2.5 x 10(-15) fractional uncertainty represents the most accurate measurement of a neutral-atom-based optical transition frequency to date.