We present the observation of three semi-forbidden transitions in singly-ionized ytterbium from the metastable $^{2}\mathrm{F}^o_{7/2}$ state. Owing to the long lifetimes of both the upper and lower states involved, these transitions are narrow and complement those already frequently used in this atom for quantum information and searches for new physics. We report the absolute frequencies of these electric quadrupole transitions, their isotope shifts, hyperfine structure, and measurements of the quadrupole transition moments. We find that the spontaneous lifetimes of these excited states are limited by slow magnetic dipole emission to lower-lying, odd-parity states, the lowest of which is accessible by laser excitation from ${}^2\mathrm{F}_{7/2}^o$ and is an attractive candidate for hosting a long-lived qubit.
We present the observation of three semi-forbidden transitions in singly-ionized ytterbium from the metastable 2F7/2o state. Owing to the long lifetimes of both the upper and lower states involved, these transitions are narrow and complement those already frequently used in this atom for quantum information and searches for new physics. We report the absolute frequencies of these electric quadrupole transitions, their isotope shifts, hyperfine structure, and measurements of the quadrupole transition moments. We find that the spontaneous lifetimes of these excited states are limited by slow magnetic dipole emission to lower-lying, odd-parity states, the lowest of which is accessible by laser excitation from 2F7/2o and is an attractive candidate for hosting a long-lived qubit.
We present the observation of three semiforbidden transitions in singly ionized ytterbium from the metastable ^{2}F_{7/2}^{o} state. Owing to the long lifetimes of both the upper and lower states involved, these transitions are narrow and complement those already frequently used in this atom for quantum information and searches for new physics. We report the absolute frequencies of these electric quadrupole transitions, their isotope shifts, hyperfine structure, and measurements of the quadrupole transition moments. We find that the spontaneous lifetimes of these excited states are limited by slow magnetic dipole emission to lower-lying, odd-parity states, the lowest of which is accessible by laser excitation from ^{2}F_{7/2}^{o} and is an attractive candidate for hosting a long-lived qubit.
We report on the first coherent excitation of the highly forbidden ${^{2}S}_{1/2}\ensuremath{\rightarrow}{^{2}F}_{7/2}$ electric octupole (E3) transition in a single trapped 172Yb+ ion, an isotope without nuclear spin. Using the transition in 171Yb+ as a reference, we determine the transition frequency to be 642 116 784 950 887.6(2.4) Hz. We map out the magnetic field environment using the forbidden ${^{2}S}_{1/2}\ensuremath{\rightarrow}{^{2}D}_{5/2}$ electric quadrupole (E2) transition and determine its frequency to be 729 476 867 027 206.8(4.4) Hz. Our results are a factor of $1\ifmmode\times\else\texttimes\fi{}{10}^{5}$ ($3\ifmmode\times\else\texttimes\fi{}{10}^{5}$) more accurate for the E2 (E3) transition compared to previous measurements. The results open up the way to search for new physics via precise isotope shift measurements and improved tests of local Lorentz invariance using the metastable 2F7/2 state of Yb+.
We report the coherent excitation of the highly forbidden ^{2}S_{1/2}→^{2}F_{7/2} clock transition in the odd isotope ^{173}Yb^{+} with nuclear spin I=5/2, and reveal the hyperfine-state-dependent, nuclear-spin-induced quenching of this transition. The inferred lifetime of the F_{e}=4 hyperfine state is one order of magnitude shorter than the unperturbed ^{2}F_{7/2} clock state of ^{171}Yb^{+}. This reduced lifetime lowers the required optical power for coherent excitation of the clock transition, thereby reducing the ac Stark shift caused by the clock laser. Using a three-ion Coulomb crystal, we experimentally demonstrate an approximately twentyfold suppression of the ac Stark shift, a critical improvement for the scalability of future multi-ion Yb^{+} clocks. Furthermore, we report the |^{2}S_{1/2},F_{g}=3⟩→|^{2}F_{7/2},F_{e}=6⟩ unquenched reference transition frequency as 642.11917656354(43) THz, along with the measured hyperfine splitting and calculated quadratic Zeeman sensitivities of the ^{2}F_{7/2} clock state. Our results pave the way toward multi-ion optical clocks and quantum computers based on ^{173}Yb^{+}.
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.
We present spectroscopic data for four metastable state clear-out transitions between 399 nm and 412 nm for all even long-lived isotopes of Yb+ as well as their hyperfine structure in 171Yb+. The strong ${}^{2}{D}_{3/2}\ensuremath{\rightarrow}{}^{1}{[1/2]}_{1/2}$ transition at 412 nm represents an attractive alternative for the standard 935 nm repumper used in cooling and trapping experiments, while the transition to the 3[3/2]3/2 state at 411 nm clears out the 2F7/2 state, for which typically 638 nm or 760 nm is used. These two alternative transitions simplify the experimental setup by removing the need for infrared optics to cool and manipulate Yb+ and may be of particular interest when considering integrated photonics solutions. We also present data for the transitions $^{2}D_{3/2}\ensuremath{\rightarrow}{}^{3}{[1/2]}_{3/2}$ at 399 nm and $^{2}D_{3/2}\ensuremath{\rightarrow}{}^{1}{[5/2]}_{5/2}$ at 410 nm including decay branching ratios of the excited states.
We report an experimental observation of the weak 'SO-~PO transition in 171,173Ybl and new approaches for qubits and optical clocks with this single-photon resonance and a three-photon resonance in an even isotope, respectively. Introduction - Optical clocks show great promise as the next generation of precision frequency standards due to the high frequency and correspondingly high line-Q of weakly allowed atomic transitions. Thanks to femtosecond comb technology (l), clocks based on optical transitions in both single trapped ions and neutral atom clouds are poised to exceed the already stringent bounds on precision set by microwave frequency standards. A recent proposal combining the Lamb-Dicke confinement of single ion frequency standards with the high signal-tenoise of neutral atom cLouds, and exploiting a highly forbidden transition insensitive to external magnetic fields and trap light polarization has the potential to do even better (2). The scheme makes use of the 'SO-~P~ electric dipole transition in alkaline-earth atoms, weakly allowed in odd isotopes by the hyperfine interaction of the nuclear spin and completely forbidden by a single-photon process in even isotopes. Trapping the atoms in a Stark-free optical httice will allow a large ensemble of atoms to exhibit a spectrum free of Doppler and recoil shifts, leading to an estimated accuracy of a few parts in lo1* (3, 41. As an additional application, the long atomic coherence times in optical lattices also suggest using the 'SO-~PO pairs of states as an array of qubits for quantum information (5, 61. Yb and Sr are both strong candidates for an optical lattice clock as well as for creating useful qubits. Both atoms have experimentally accessible energy level transitions, allowing the atoms to be readily laser-cooled and trapped, and in the case of Yb, Eose-Einstein condensed. While the Sr clock transition has been studied extensively, both in and out of an optical lattice, the same transition in Yb has thus far remained unexplored experimentally. Here we report the direct excitation of the 578 nm 'SO-~P~ transition in odd isotope 171,173Yb. (We understand that a group at NIST has also observed this transition (7)). We also discuss the possible application of this type of transitions in making qubits for quantum computation and a clock scheme based on three-photon transition in an even isotope (8, 91. - The level structure of Yb and the experimental apparatus are diagrammed in Fig. 1. The experiment is performed on a sample of cold atoms collected in a magneto- optical trap (MOT). To excite the clock transition, we shut off the MOT beams and irradiate the cloud of atoms with a 578 nm probe. JVe t,hen turn the MOT beams back on, continuously monitoring 399 nm fluorescence from the atom cloud. As the probe laser frequency is scanned over the dock transition, there is an observable decrease in MOT fluorescence as atoms are excited into the metastable 3Po state and escape the trap. By chopping trap and probe beams out of phase, we avoid light shifts of the clock transition due to near-resonant 399 nm light while maintaining a steady-state MOT population. The MOT fluorescence reduction of 171Yb is shown in Fig. 2 (a). Since iodine lines have been well measured in Observation of the 1So-3P, Transition in 1713173Yb