Fluorescence of optically pumped trapped ions

Gang Shu, Nathan Kurz, Matthew Dietrich +1 more

Juha Javanainen

Nicolás A. Nuñez Barreto, Lucas Giardino, Carla Crucianelli +3 more

In this paper, we present a method to measure transient fluorescent dynamics with single trapped ions in a Paul trap. We use 40 Ca + ions that exhibit a Λ-type three-level system and measure the characteristic optical pumping times between the ground S 1/2 and the meta-stable D 3/2 levels. We prepare one of these states and then pump it to the opposite via the excited P 1/2 state. By measuring the scattered photons of the ion, we retrieve transient curves of the atomic fluorescence. These curves provide fundamental information about the atomic system, such as branching fractions and excited-state lifetimes, as well as experimental parameters like the efficiency of the detection system and the saturation parameter of one of the transitions. Finally, we study the time-dependent fluorescence as a function of optical power and detuning of the lasers and find a very good agreement with simulating the dynamics via a three-level open quantum system through a set of optical Bloch equations. Being able to record time-dependent fluorescence is of particular interest as it contains information about the temperature, cooling, and heating dynamics of the ion.

Ch. Schneider, Martin Enderlein, Thomas M. Huber +1 more

Susanna Todaro, Varun Boehm Verma, Katherine C. McCormick +7 more

We report high-fidelity state readout of a trapped ion qubit using a trap-integrated photon detector. We determine the hyperfine qubit state of a single ^{9}Be^{+} ion held in a surface-electrode rf ion trap by counting state-dependent ion fluorescence photons with a superconducting nanowire single-photon detector fabricated into the trap structure. The average readout fidelity is 0.9991(1), with a mean readout duration of 46 μs, and is limited by the polarization impurity of the readout laser beam and by off-resonant optical pumping. Because there are no intervening optical elements between the ion and the detector, we can use the ion fluorescence as a self-calibrated photon source to determine the detector quantum efficiency and its dependence on photon incidence angle and polarization.

T. Schneider, Bernhard Roth, Michael G. Hansen +5 more

This study demonstrates an all-optical internal state cooling scheme for HD+molecular ions in the rovibrational ground state using a 5.484 mum cw-quantum cascade laser. Resonance-enhanced multi-photon dissociation is used to selectively remove the ground-state HD+ions from the trap. The efficiency of the pumping scheme is investigated by comparing the corresponding changes in fluorescence with and without an optical pumping phase preceding the detection. An increase in the relative fluorescence decay by a factor of 3 is observed with optical pumping.