133 Ba + has been identified as an attractive ion for quantum information processing due to the unique combination of its spin-1/2 nucleus and visible wavelength electronic transitions. Using a microgram source of radioactive material, we trap and laser-cool the synthetic A = 133 radioisotope of barium II in a radio-frequency ion trap. Using the same, single trapped atom, we measure the isotope shifts and hyperfine structure of the 6 2 P 1/2 ↔ 6 2 S 1/2 and 6 2 P 1/2 ↔ 5 2 D 3/2 electronic transitions that are needed for laser cooling, state preparation, and state detection of the clockstate hyperfine and optical qubits. We also report the 6 2 P 1/2 ↔ 5 2 D 3/2 electronic transition isotope shift for the rare A = 130 and 132 barium nuclides, completing the spectroscopic characterization necessary for laser cooling all long-lived barium II isotopes.Since the demonstration of the first CNOT gate over 20 years ago [1], trapped ion quantum information processing (QIP), including quantum simulation, has developed considerably [2], recently demonstrating fullyprogrammable quantum processors [3,4]. To date, qubits have been demonstrated in trapped ion hosts of all nonradioactive, alkaline-earth-like elements [1,[5][6][7][8][9][10][11][12]. These ions possess a simple electronic structure that facilitates straightforward laser cooling as well as quantum state preparation, manipulation, and readout via electromagnetic fields.For the coherent manipulation of qubits, the phase of this applied electromagnetic field must remain stable with respect to the qubit phase evolution. Thus, atomic hyperfine structure is a natural choice for the definition of a qubit, as these extremely long-lived states can be manipulated with easily-generated, phase-coherent microwave radiation. In particular, qubits defined on the hyperfine structure of ions with half-integer nuclear spin possess a pair of states with no projection of the total angular momentum (F ) along the magnetic field (m F = 0). These so-called "clock-state" qubits are well-protected from magnetic field noise and can yield coherence times exceeding 10 minutes [13,14]. Further, for these species, F = 0 ground and excited states only occur when the nuclear spin I = 1/2. This is desirable because the F = 0 ↔ F = 0 selection rule can be leveraged to produce fast, robust qubit state preparation and readout that relies solely on frequency selectivity [10,12].Among the alkaline-earth-like elements, only three (Cd, Hg, Yb) have naturally occurring I = 1/2 isotopes. Mercury and cadmium ions require lasers in the deep ultraviolet portion of the electromagnetic spectrum, making it difficult to integrate them into a large-scale QIP architecture. Since 171 Yb + has the longest laser-cooling wavelength at 370 nm, it has been used in a wide variety of groundbreaking QIP experiments [4,[15][16][17][18][19]. However, even at this ultraviolet wavelength, the use of photonics infrastructure developed for visible and infrared light is limited. For example, significant fiber attenuation limits t...
The recently demonstrated trapping and laser cooling of 133 Ba + has opened the door to the use of this nearly ideal atom for quantum information processing. However, before high fidelity qubit operations can be performed, a number of unknown state energies are needed. Here, we report measurements of the 2 P 3/2 and 2 D 5/2 hyperfine splittings, as well as the 2 P 3/2 ↔ 2 S 1/2 and 2 P 3/2 ↔ 2 D 5/2 transition frequencies. Using these transitions, we demonstrate high fidelity 133 Ba + hyperfine qubit manipulation with electron shelving detection to benchmark qubit state preparation and measurement (SPAM). Using single-shot, threshold discrimination, we measure an average SPAM fidelity of F = 0.99971(6), a factor of ≈ 2 improvement over the best reported performance of any qubit.
The extreme miniaturization of a cold-atom interferometer accelerometer requires the development of novel technologies and architectures for the interferometer subsystems. Here, we describe several component technologies and a laser system architecture to enable a path to such miniaturization. We developed a custom, compact titanium vacuum package containing a microfabricated grating chip for a tetrahedral grating magneto-optical trap (GMOT) using a single cooling beam. In addition, we designed a multi-channel photonic-integrated-circuit-compatible laser system implemented with a single seed laser and single sideband modulators in a time-multiplexed manner, reducing the number of optical channels connected to the sensor head. In a compact sensor head containing the vacuum package, sub-Doppler cooling in the GMOT produces 15 μK temperatures, and the GMOT can operate at a 20 Hz data rate. We validated the atomic coherence with Ramsey interferometry using microwave spectroscopy, then demonstrated a light-pulse atom interferometer in a gravimeter configuration for a 10 Hz measurement data rate and T = 0–4.5 ms interrogation time, resulting in Δg/g = 2.0 × 10−6. This work represents a significant step towards deployable cold-atom inertial sensors under large amplitude motional dynamics.
Compact cold-atom sensors depend on vacuum technology. One of the major limitations to miniaturizing these sensors is the active pumps—typically ion pumps—that are required to sustain the low pressure needed for laser cooling. Although passively pumped chambers have been proposed as a solution to this problem, technical challenges have prevented successful operation at the levels needed for cold-atom experiments. The authors present the first demonstration of a vacuum package successfully independent of ion pumps for more than a week; their vacuum package is capable of sustaining a cloud of cold atoms in a magneto-optical trap (MOT) for greater than 200 days using only non-evaporable getters and a rubidium dispenser. Measurements of the MOT lifetime indicate that the package maintains a pressure of better than 2×10−7 Torr. This result will significantly enable the development of compact atomic sensors, including those sensitive to magnetic fields, where the absence of an ion pump will be advantageous.
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