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arXiv:physics/0703067 · Physical Review Letters

Observation of the S01→P03 Clock Transition in Al+27

Till Rosenband, Piet O. Schmidt, David B. Hume, Wayne M. Itano, Tara M. Fortier, J. E. Stalnaker, Kihwan Kim, Scott A. Diddams, Jeroen C. J. Koelemeij, Jonas Bergquist, David J. Wineland

Published May 31, 2007• 231 citations
arXivHTMLPDF

Abstract

We report, for the first time, laser spectroscopy of the 1S0-->3P0 clock transition in 27Al+. A single aluminum ion and a single beryllium ion are simultaneously confined in a linear Paul trap, coupled by their mutual Coulomb repulsion. This coupling allows the beryllium ion to sympathetically cool the aluminum ion and also enables transfer of the aluminum's electronic state to the beryllium's hyperfine state, which can be measured with high fidelity. These techniques are applied to measure the clock transition frequency nu=1,121,015,393,207,851(6) Hz. They are also used to measure the lifetime of the metastable clock state tau=20.6+/-1.4 s, the ground state 1S0 g factor gS=-0.000,792,48(14), and the excited state 3P0 g factor gP=-0.001,976,86(21), in units of the Bohr magneton.

DOI
10.1103/physrevlett.98.220801

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We report, for the first time, laser spectroscopy of the 1S0-->3P0 clock transition in 27Al+. A single aluminum ion and a single beryllium ion are simultaneously confined in a linear Paul trap, coupled by their mutual Coulomb repulsion. This coupling allows the beryllium ion to sympathetically cool the aluminum ion and also enables transfer of the aluminum's electronic state to the beryllium's hyperfine state, which can be measured with high fidelity. These techniques are applied to measure the clock transition frequency nu=1,121,015,393,207,851(6) Hz. They are also used to measure the lifetime of the metastable clock state tau=20.6+/-1.4 s, the ground state 1S0 g factor gS=-0.000,792,48(14), and the excited state 3P0 g factor gP=-0.001,976,86(21), in units of the Bohr magneton.
We report the realization of quantum logic spectroscopy on the 1 S 0→ 3 P 0 clock transition of a single 27 Al + ion. This ion is trapped together with a 40 Ca + ion in a linear Paul trap, coupled by Coulomb repulsion, which provides sympathetic Doppler laser cooling and also the means for internal state detection of the clock state of the 27 Al + ion. A repetitive quantum nondemolition measurement is performed to improve the fidelity of state detection. These techniques are applied to obtain clock spectroscopy at approximately 45 Hz. We also perform the preliminary locking on the 1 S 0 → 3 P 0 clock transition. Our work is a fundamental step that is necessary toward obtaining an ultra-precision quantum logic clock based on 40 Ca +-27 Al + ions.
We perform quantum logic spectroscopy with a 27 Al + / 40 Ca + mixed ion crystal in a linear Paul trap for a measurement of the intercombination transition in 27 Al + . Towards this end, Ramsey spectroscopy is used for probing the transition in 27 Al + and the clock transition in 40 Ca + in interleaved measurements. By using the precisely measured frequency of the clock transition in 40 Ca + as a frequency reference, we determine the frequency of the intercombination line to be = 1 122 842 857 334 736 (85) Hz and the Landé g -factor of the excited state to be = 0.428 133(2).
Magnesium ion which acts as the logic ion in27Al+ion optical clock is trapped and laser cooled in a linear ion trap. Rabi oscillation between two hyperfine ground states of25Mg+ion is observed and resonant frequency between two hyperfine ground states of25Mg+ion is measured. Earth magnetic field is compensated with three pairs of mutually perpendicular Helmholtz coils. Light shift induced by the Raman cooling beams is measured. With the photo-ionization laser of Al, Al+ion is trapped together with Mg+ion. The linewidth of the clock laser of the27Al+ion is measured to be about 0.8 Hz. The Allan deviation of the beat note from two independent lasers is 6.5×10-15at 1s.
We report the direct excitation of the highly forbidden (6s2) 1S0 <--> (6s6p) 3P0 optical transition in two odd isotopes of neutral ytterbium. As the excitation laser frequency is scanned, absorption is detected by monitoring the depletion from an atomic cloud at approximately 70 microK in a magneto-optical trap. The measured frequency in 171Yb (F=1/2) is 518,295,836,591.6 +/- 4.4 kHz. The measured frequency in 173Yb (F=5/2) is 518,294,576,847.6 +/- 4.4 kHz. Measurements are made with a femtosecond-laser frequency comb calibrated by the National Institute of Standards and Technology cesium fountain clock and represent nearly a 10(6)-fold reduction in uncertainty. The natural linewidth of these J=0 to J=0 transitions is calculated to be approximately 10 mHz, making them well suited to support a new generation of optical atomic clocks based on confinement in an optical lattice.
Direct measurements of the ground-state magnetically insensitive hyperfine transition | F = 2 , m F = 0 〉 → | F = 1 , m F = 0 〉 of Be + 9 ions have been performed using microwave-driven state transfer. The Be + 9 ions are confined and laser cooled in a linear Paul trap, forming a Coulomb crystal. The transition frequencies have been measured over a magnetic-field range of ± 0.5 mT centered at zero magnetic field and the acquired data were fitted accounting for the high-order Zeeman effect. The hyperfine constant A is determined to be − 625.008 840 ( 35 ) MHz, achieving a relative precision of 5.6 × 10 − 8 .
Single ions trapped and laser cooled provide ideal objects for high resolution spectroscopy and frequency standards. For the latter purpose we are investigating the 5s2 1S0 → 5s5p 3P0 transition of In+. With a natural linewidth of only 1.1 Hz this resonance offers very high resolution and is highly immune to frequency shifts due to external electromagnetic fields, because it connects two levels with vanishing electronic magnetic momenta [1]. The wavelength of this clock transition is 236.5 nm and is technically very convenient, since it coincides with the fourth harmonic of the 946 nm Nd:YAG laser line. So this intrinsically frequency stable solid-state laser can be used to excite the transition [2]. For laser cooling and fluorescence detection of the indium ion the 5s2 1So -> 5s5p 3P1 transition at 230.6 nm can be employed. The use of the relatively narrow intercombination line for laser cooling allows us to study optical sideband cooling in the strong binding regime, where the oscillation frequencies of the ion in the trap (around 1 MHz) are larger than the optical linewidth of 360 kHz. In this parameter range laser cooling is possible to the quantum ground state of the vibrational motion in the trap corresponding to a temperature of roughly 100 μK. The same low temperature was obtained with sideband cooling of a small Coulomb crystal consisting of two ions, creating an interesting new quantum few-particle system.