We measure ion heating following transport throughout a Y-junction surface-electrode ion trap. By carefully selecting the trap voltage update rate during adiabatic transport along a trap arm, we observe minimal heating relative to the anomalous heating background. Transport through the junction results in an induced heating between 37 and 150 quanta in the axial direction per traverse. To reliably measure heating in this range, we compare the experimental sideband envelope, including up to fourth-order sidebands, to a theoretical model. The sideband envelope method allows us to cover the intermediate heating range inaccessible to the first-order sideband and Doppler recooling methods. We conclude that quantum information processing in this ion trap will likely require sympathetic cooling in order to support high fidelity gates after junction transport. measurements for a stationary ion, ion motion in the linear region, and ion motion through the junction. In Sec. V, we conclude with a discussion of trap robustness and potential future directions.

We present a measurement of the branching ratios from the 6P 3/2 state of BaII into all dipoleallowed decay channels (6S 1/2 , 5D 3/2 and 5D 5/2 ). Measurements were performed on single 138 Ba + ions in a linear Paul trap with a frequency-doubled mode-locked Ti:Sapphire laser resonant with the 6S 1/2 → 6P 3/2 transition at 455 nm by detection of electron shelving into the dark 5D 5/2 state. By driving a π Rabi rotation with a single femtosecond pulse, an absolute measurement of the branching ratio to 5D 5/2 state was performed. Combined with a measurement of the relative decay rates into 5D 3/2 and 5D 5/2 states performed with long trains of highly attenuated 455 nm pulses, it allowed the extraction of the absolute ratios of the other two decays. Relative strengths normalized to unity are found to be 0. Single trapped ions are a valuable physical system for many applications including quantum computation [1,2], frequency standards, optical metrology [3], precision searches for drifts in fundamental constants [4] and tests of exotic physical theories [5]. Among the advantages over alternatives are their long trapping lifetimes and the relative ease of confining single ions to a small volume in a trap, thereby reducing the systematic effects and negating the need for quantum statistics. The barium ion, particularly the odd 137 isotope with nuclear spin 3/2, has been proposed for use in quantum computation schemes with the hyperfine levels of the 6S 1/2 ground state for the qubit, as an optical frequency standard with a 2051 nm clock transition from 6S 1/2 , F = 2, m F = 0 to 5D 3/2 , F = 0, and as a test of parity-nonconservation with a small dipole coupling between the otherwise dipole-forbidden 6S 1/2 → 5D 3/2 transition [5,6,7].Accurate models of atomic wave functions which include many-body interactions are necessary to calculate dipole and quadrupole matrix elements that appear in the calculations of transition rates, energy level shifts and line widths in the experiments mentioned above. Measurements of branching ratios represent a better quantity from which to verify such values than, for example, precise measurements of the lifetimes of metastable states. They are less prone to systematic uncertainties such as background gas quenching and stray fields to which the long waiting times (tens of seconds) required to accurately measure lifetimes are sensitive. Here we present a single-ion measurement of the branching ratios from the 6P 3/2 state of 138 Ba + to the three states allowed via dipole transitions, 6S 1/2 , 5D 3/2 and 5D 5/2 .A schematic of the optical and electronic arrangement of the experimental apparatus can be found in Fig. 1. The ion trap itself is a linear Paul trap with radiofrequency quadrupole confining potential and DC voltage end caps in ultra high vacuum with operating pressures of about 10 −11 torr. The trap dimensions are ∼ 0.5 mm radially and ∼ 3.3 mm axially. At ∼ 0.5 W of inductivelycoupled RF power at ∼ 32 MHz and 100 V end cap potential, the trap secular frequencies are measured to...

We demonstrate sympathetic sideband cooling of a 40 CaH + molecular ion co-trapped with a 40 Ca + atomic ion in a linear Paul trap. Both axial modes of the two-ion chain are simultaneously cooled to near the ground state of motion. The center of mass mode is cooled to an average quanta of harmonic motion = ± n 0.13 0.03 COM

State preparation, qubit rotation, and high fidelity readout are demonstrated for two separate 137 Ba + qubit types. First, an optical qubit on the narrow 6S 1/2 to 5D 5/2 transition at 1.76 µm is implemented. Then, leveraging the techniques developed there for readout, a ground state hyperfine qubit using the magnetically insensitive transition at 8 GHz is accomplished.

Molecular ions can be held in a chain of laser-cooled atomic ions by sympathetic cooling. This system is ideal for performing high-precision molecular spectroscopy with applications in astrochemistry and fundamental physics. Here we show that this same system can be coupled with a broadband laser to discover new molecular transitions. We use three-ion chains of Ca+ and CaH+ to observe vibrational transitions via resonance-enhanced multiphoton dissociation detected by Ca+ fluorescence. On the basis of theoretical calculations, we assign the observed peaks to the transition from the ground vibrational state, ν=0 to ν=9 and 10. Our method allows us to track single-molecular events, and it can be extended to work with any molecule by using normal mode frequency shifts to detect the dissociation. This survey spectroscopy serves as a bridge to the precision spectroscopy required for molecular ion control.