We demonstrate precision laser spectroscopy of a trapped $^{173}$Yb$^+$ ion that is not directly laser cooled by coupling it to ultracold atoms. The atomic bath continuously cools the internal degrees of freedom of the ion to its hyperfine ground state via spin-exchange collisions. Successful laser excitation is detected via state-selective charge transfer and subsequent ion loss. We probe the $6^2S_{1/2}\rightarrow 6^2P_{3/2}$ transition at 329 nm and measure the magnetic and electric hyperfine interaction constants for the $6^2P_{3/2}$ state to be $A=-241(1)$ MHz and $B=1460(8)$ MHz, respectively. Our results are in agreement with a previous measurement obtained in a hollow-cathode discharge experiment but are a factor of 6-9 more precise. The techniques demonstrated in this work may be extended to perform precision spectroscopy on other ions with complex level structures.
Precision spectroscopy of a trapped 173Yb+ ion using a bath of ultracold atoms
We demonstrate precision laser spectroscopy of a trapped 173Yb+ ion that is not directly laser cooled by coupling it to ultracold atoms. The atomic bath continuously cools the internal degrees of freedom of the ion to its hyperfine ground state via spin-exchange collisions. Successful laser excitation is detected via state-selective charge transfer and subsequent ion loss. We probe the 62S1/2→62P3/2 transition at 329 nm and measure the magnetic and electric hyperfine interaction constants for the 62P3/2 state to be A=−241(1) MHz and B=1460(8) MHz, respectively. Our results are in agreement with a previous measurement obtained in a hollow-cathode discharge experiment but are a factor of 6-9 more precise. The techniques demonstrated in this work may be extended to perform precision spectroscopy on other ions with complex level structures.
High-Resolution Spectroscopy of 173Yb+ Ions
Compared to other stable isotopes of Yb+, 173Yb+ has a richer hyperfine structure, which leads to more favorable clock transitions, spectroscopic techniques for probing new physics, and more sophisticated quantum computing architectures. However, to date, its electronic spectrum remains poorly characterized. Here, we report on efficient laser cooling, state preparation, and detection of a single trapped 173Yb+ ion. The previously unobserved 2S1/2→2D3/2 electric quadrupole transition at 436 nm is coherently excited, and the isotope shift between 171Yb+ and 173Yb+ on this transition is determined with an uncertainty of 1.4 Hz. Using microwave spectroscopy, we resolve the hyperfine structure (HFS) of the 2D3/2 state with a relative uncertainty below 10−8. From the HFS measurement data, we infer for 173Yb a nuclear magnetic octupole moment Ω=−0.062(8)(b×μN) with uncertainty reduced by more than 2 orders of magnitude compared to previous studies. The data also allow us to determine hyperfine anomalies for the 2S1/2 and 2D3/2 states.
Trapped ions are currently one of the most promising architectures for realising the quantum information processor. The long lived internal states are ideal for representing qubit states and, through controlled interactions with electromagnetic radiation, ions can be manipulated to execute coherent logic operations. In this thesis an experiment capable of trapping Yb+ ions, including 171Yb+, is presented. Since ion energy can limit the coherence of qubit manipulations, characterisation of an ion trap heating rate is vital. Using a trapped 174Yb+ ion a heating rate consistent with previous measurements of other ion species in similar ion traps is obtained. This result shows abnormal heating of Yb+ does not occur, further solidifying the suitability of this species for quantum information processing. Efficient creation, and cooling of trapped ions requires exact wavelengths for the ionising, cooling and repump transitions. A simple technique to measure the 1S0 ? 1P1 transition wavelengths, required for isotope selective photoionisation of neutral Yb, is developed. Using the technique new wavelengths, accurate to 60 MHz, are obtained and differ from previously published results by 660 MHz. Through a simple modification the technique can also predict Doppler shifted transition frequencies, which may be required in non-perpendicular atom-laser interactions. Using trapped ions, the 2S1=2 ? 2P1/2 Doppler cooling and 2D3/2 ? 2D[3/2]1/2 repump transitions are also measured to a greater accuracy than previously reported. Many experiments require wavelengths which can only be obtained using complex expensive laser systems. To remedy this a simple cost effective laser is developed to enable laser diodes to be operated at sub zero temperatures, extending the range of obtainable wavelengths. Additional diode modulation capabilities allow for the manipulation of atoms and ions with hyperfine structures. The laser is shown to be suitable for manipulating Yb+ ions by cooling a diode from 372 nm to 369 nm and simultaneously generating 2.1 GHz frequency sidebands. Coherent manipulation such as arbitrary qubit rotations, motional coupling and ground state cooling, are required for trapped ion quantum computing. Two photon stimulated Raman transitions are identified as a suitable technique to implement all of these requirements and an investigation into implementing this technique with 171Yb+ is conducted. The possibility of exciting a Raman transition via either a dipole or quadrupole transitions in 171Yb+ is analysed, with dipole transitions preferred because quadrupole transitions are found to be too demanding experimentally. An inexpensive setup, utilising a dipole transition, is designed and tested. Although currently limited the setup shows potential to be an inexpensive, high fidelity method of exciting a Raman transition.
We report on spectroscopic results on the $^{2}S_{1/2}\ensuremath{\rightarrow}\phantom{\rule{0.16em}{0ex}}^{2}P_{3/2}$ transition in single trapped Yb+ ions. We measure the isotope shifts for all stable Yb+ isotopes except 173Yb+, as well as the hyperfine splitting of the 2P3/2 state in 171Yb+. Our results are in agreement with previous measurements but are a factor of 5--9 more precise. For the hyperfine constant A(2P3/2)=875.4(10)MHz our results also agree with previous measurements but deviate significantly from theoretical predictions. We present experimental results on the branching ratios for the decay of the 2P3/2 state. We find branching fractions for the decay to the 2D3/2 state and 2D5/2 state of 0.17(1)% and 1.08(5)%, respectively, in rough agreement with theoretical predictions. Furthermore, we measured the isotope shifts of the $^{2}F_{7/2}\ensuremath{\rightarrow}^{1}D{[5/2]}_{5/2}$ transition and determine the hyperfine structure constant for the 1D[5/2]5/2 state in 171Yb+ to be $A(^{1}D{[5/2]}_{5/2})=\ensuremath{-}107(6)\phantom{\rule{4pt}{0ex}}\mathrm{MHz}$.
Precision measurement of the ground-state hyperfine constant for 9Be+ in a linear Paul trap via magnetically insensitive hyperfine transitions
Direct measurements of the ground-state magnetically insensitive hyperfine transition |F=2,mF=0>->|F=1,mF=0> of 9Be+ ions have been performed using microwave-driven state transfer. The 9Be+ 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 $ \pm 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 -625.008840(35) MHz, achieving a relative precision of $ 5.6 \times 10^{-8}$.
We discuss the Ca+ ion as a simple atomic system, described as an electronic three-level system. In a Paul ion trap a small ion cloud can be laser cooled until crystallisation appears which reduces the ion motion. Lifetime and hyperfine structure measurements in ground and excited electronic states can be performed with high precision. A first example for the investigation of a complex ionic system is represented by the Eu+ ion, where hyperfine structure splittings have been obtained with uncertainties in the 10−9 range even on radioactive isotopes with few available particles. These small uncertainties require extensive and complicated pertubation calculation for a determination of coupling constant, but open the way for detailed investigation of nuclear structure effects.
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 .