Identification of molecular quantum states using phase-sensitive forces

Abstract

Quantum-logic techniques used to manipulate quantum systems are now increasingly being applied to molecules. Previous experiments on single trapped diatomic species have enabled state detection with excellent fidelities and highly precise spectroscopic measurements. However, for complex molecules with a dense energy-level structure improved methods are necessary. Here, we demonstrate an enhanced quantum protocol for molecular state detection using state-dependent forces. Our approach is based on interfering a reference and a signal force applied to a single atomic and molecular ion. By changing the relative phase of the forces, we identify states embedded in a dense molecular energy-level structure and monitor state-to-state inelastic scattering processes. This method can also be used to exclude a large number of states in a single measurement when the initial state preparation is imperfect and information on the molecular properties is incomplete. While the present experiments focus on N$${}_{2}^{+}$$ 2 + , the method is general and is expected to be of particular benefit for polyatomic systems.

Quantum-Logic Detection of Chemical Reactions

“…Charge exchange rates between an ensemble of molecular ions and ensemble of ultra-cold atoms were measured using sympathetic cooling and logic mass spectroscopy via co-trapped ions [42]. Another work traced molecular association of a single cold molecular ion with room-temperature gas using quantum logic [43]. Other recent proposals suggested to employ variation of quantum logic for coherent manipulation of the molecule using phonon resolved transitions [44], and to study the Al + optical clock transition during its interaction with ultracold atoms [45].…”

Non-destructive State Detection and Spectroscopy of Single Molecules

“…In order to overcome these shortcomings, we have developed novel technologies for the quantum-manipulation of single molecules. [27][28][29] We have adapted quantum-logic techniques [30] in which a single molecular ion is simultaneously trapped with a single laser-cooled atomic ion in a radiofrequency (rf) quadrupole ion trap. [29] The cooling and state detection of the molecular ion is mediated via the atomic ion through their mutual Coulomb interaction which is also employed in related quantum-logic experiments with both atomic [31] and molecular ions.…”

“…Here, one of the modes of the Ca + -N + 2 string was cooled sympathetically to its quantum-mechanical ground state by driving its sidebands on the (4s) 2 S 1/2 → (3d) 2 D 5/2 electronic transition in Ca + . [29] The ODF for state detection in our experiments [27][28][29] was implemented by two counter-propagating laser beams which formed a one-dimensional optical lattice. The strength of the ODF is enhanced when the optical frequency of the lattice is near a strong spectroscopic resonance in the molecule.…”

“…Further details about the experimental implementation of the technique can be found in refs. [27][28][29].…”

Electric-field dissociation of weakly bound molecular ions

“…The advent of hybrid neutral-ion traps has boosted cold chemistry research due to the possibility of bringing together ions and atoms in a controlled manner [1][2][3][4][5]. Similarly, these traps find applications in different research areas such as the development of new and more efficient quantum information protocols [6][7][8][9][10][11][12][13], the realization of quantum logic spectroscopy schemes [14][15][16][17][18][19][20] and the study of impurity physics [21][22][23][24][25][26][27][28][29], to cite a few. On the impurity physics front, when a single charged impurity, A + , is brought in contact with an ultracold atomic gas B, at sufficient densities, the ion undergoes a three-body recombination reaction: A + + B + B→ AB + + B leading to the formation of weakly bound molecular ions [1,30,31].…”