In this paper, we present a detailed method for rapidly and effectively loading a single 40 Ca + ion into a miniature linear Paul trap. Calcium atoms are generated by laser ablation, and the single ion is loaded and specific isotopes are selected by a two-step photo-ionization method. Compared to the traditional photo-ionization method in which atoms are typically emitted from a resistively heated oven, the advantages of laser ablation are that it can be precisely controlled, it can effectively avoid the problem of fluxed calcium deposition on the trap electrodes, and it restricts the generation of dark ions, which can influence atomic-precision spectroscopy measurements. With its short loading time, it is possible to load an ion in few seconds with the appropriate parameters. The technique of laser ablation has been applied to generate several species of atoms and ions at present, it will potentially benefit in the studies of optical frequency standards, quantum simulation and quantum information processing in an ultra-high vacuum condition and cryogenic system.
Rare calcium isotope 43Ca+ ion (0.135%) is the only naturally abundant isotope with hyperfine structure. This isotope is considered an attractive candidate both for an optical frequency standard and for quantum information processing. We report a method to load 43Ca+ ions selectively into a linear Paul trap using a two-step, resonant photo-ionization process. Isotope selectivity is achieved by utilizing the isotope shifts for the resonant 4s2 1S0-4s4p 1P1 transition of neutral calcium. The second non-resonant excitation is achieved by an ultraviolet light emitting diode (LED). The use of an LED is simpler and more economical than using a laser for the second transition. Additionally the laser cooling of 43Ca+ is demonstrated using two ultraviolet-diode lasers and two infrared-diode lasers. Due to the hyperfine structure, the laser requirements for Doppler cooling 43Ca+ are more demanding than for the other isotopes.
We report on the isotope-selective manipulation of Ca + using the laser-heating and laser-cooling techniques in a linear Paul trap. Only 40 Ca + was selectively laser-heated using the optical isotope shift and eliminated from the trap while keeping the target isotope in the trap. The elimination process of the dominant isotope 40 Ca + was investigated and 42, 43, 44, 48 Ca + in the natural isotope mixture of Ca + generated by laser ablation were successfully observed by means of applying the appropriate dc voltage on the end-cap electrodes without changing the laser frequencies, the laser powers and the duration of the laser irradiation. This simplified method enables us to efficiently laser-cool the rare isotopes.
Abstract We present a detailed method for accumulating Ca+ ions controllably in a linear Paul trap. The ions are generated by pulsed laser ablation and dynamically loaded into the ion trap by switching the trapping potential on and off. The loaded ions are precooled by buffer gas and then laser-cooled to form Coulomb crystals for verifying quantity. The number of ions is controlled by manipulating the trapping potential of the ion trap, partial pressure of buffer gas and turn-on time of the entrance end cap voltage. With single-pulse laser ablation, the number of trapped ions ranges from tens to ten thousand. The kinetic energy of loaded ions can be selected via the optimal turn-on time of the entrance end cap. Using multiple-pulse laser ablation, the number is further increased and reaches about 4 × 10 4 . The dynamic loading method has wide application for accumulating low-yielding ions via laser ablation in the ion trap.
Our work describes two most common methods of generating neutral atoms needed for experiments with trapped and cooled ions. The easiest but not most effective way of the neutral atoms generating is to use a heated oven. A better method allowing a fine control of generating atoms is to use a pulsed laser ablation. A vacuum chamber with Ca atoms source and necessary optics was assembled. Detection of generated particles was achieved by laser-induced fluorescence and sensitive camera. The paper consists of measurement of both method of generating the atoms.
The
133Ba+ ion is a promising candidate as a high-fidelity qubit, and the
137Ba+ isotope is promising as a high-fidelity qudit
(d>2). Barium metal is very reactive, and
133Ba+ is radioactive and can only be sourced in small quantities, so the most commonly used loading method, oven heating, is less suited for barium and is currently not possible for
133Ba+. Pulsed laser ablation solves both of these problems by utilizing compound barium sources while also giving some distinct advantages, such as fast loading, less displaced material, and lower heat load near the ion trap. Because of the relatively low abundances of the isotopes of interest, a two-step photoionization technique is used, which gives us the ability to selectively load isotopes. Characterization of the ablation process for our
BaCl2 targets are presented, including observation of neutral and ion ablation-fluence regimes, preparation and conditioning, lifetimes of ablation spots, and plume velocity distributions. We show that by using laser ablation on
BaCl2 salt targets with a two-step photoionization method, we can produce and trap barium ions reliably. Furthermore, we demonstrate that with our photoionization method, we can trap
137Ba+ with an enhanced selectivity compared to its natural abundance.