Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1412.0634 · Physical Review A

Reversing hydride-ion formation in quantum-information experiments with Be +

Brian C. Sawyer, Justin Bohnet, J. Britton, J. J. Bollinger

Published Jan 12, 2015• 27 citations
arXivHTMLPDF

Abstract

We demonstrate photodissociation of ${\mathrm{BeH}}^{+}$ ions within a Coulomb crystal of thousands of ${}^{9}{\mathrm{Be}}^{+}$ ions confined in a Penning trap. Because ${\mathrm{BeH}}^{+}$ ions are created via exothermic reactions between trapped, laser-cooled ${\mathrm{Be}}^{+}({}^{2}{P}_{3/2})$ and background ${\mathrm{H}}_{2}$ within the vacuum chamber, they represent a major contaminant species responsible for infidelities in large-scale trapped-ion quantum-information experiments. The rotational-state-insensitive dissociation scheme described here makes use of 157-nm photons to produce ${\mathrm{Be}}^{+}$ and H as products, thereby restoring ${\mathrm{Be}}^{+}$ ions without the need for reloading. This technique facilitates longer experiment runtimes at a given background ${\mathrm{H}}_{2}$ pressure and may be adapted for removal of ${\mathrm{MgH}}^{+}$ and ${\mathrm{AlH}}^{+}$ impurities.

DOI
10.1103/physreva.91.011401

Related papers

Determining reaction pathways at low temperatures by isotopic substitution: the case of BeD + + H2O

Tiangang Yang, Bin Zhao, Gary K Chen +3 more

Trapped Be + ions are a leading platform for quantum information science (Gaebler et al 2016 Phys. Rev. Lett. 117 060505 ), but reactions with background gas species, such as H 2 and H 2 O, result in qubit loss. Our experiment reveals that the BeOH + ion is the final trapped ion species when both H 2 and H 2 O exist in a vacuum system with cold, trapped Be + . The BeH + product in the Be + + H 2 reaction further reacts with H 2 O to form BeOH + . To understand the loss mechanism, low-temperature reactions between sympathetically cooled BeD + ions and H 2 O molecules have been investigated using an integrated, laser-cooled Be + ion trap and high-resolution time-of-flight mass spectrometer (Schneider et al 2014 Phys. Rev. Appl. 2 034013 ). Among all the possible products, BeH 2 O + , H 2 DO + , BeOD + , and BeOH + , only the BeOH + molecular ion was observed experimentally, with the assumed co-product of HD. Theoretical analyses based on explicitly correlated restricted coupled cluster singles, doubles, and perturbative triples (RCCSD(T)-F12) method with the augmented correlation-consistent polarized triple zeta (AVTZ) basis set reveal that two intuitive direct abstraction product channels, Be + H 2 DO + and D + BeH 2 O + , are not energetically accessible at the present reaction temperature (∼150 K). Instead, a double displacement BeOH + + HD product channel is accessible due to a large exothermicity of 1.885 eV through a submerged barrier in the reaction pathway. While the BeOD + + H 2 product channel has a similar exothermicity, the reaction pathway is dynamically unfavourable, as suggested by a sudden vector projection analysis. This work sheds light on the origin of the loss and contaminations of the laser-cooled Be + ions in quantum-information experiments.

arXiv:2108.05041•New Journal of Physics•Sep 29, 2021•5 citations

Two-photon dissociation of BeH + with a middle ultraviolet band laser

Qian-Yu Zhang, Wen-Li Bai, Zhi-Yuan Ao +3 more

Abstract Two-photon dissociation of BeH + ions is studied by detecting the fluorescence changes of Be + –BeH + bi-component Coulomb crystal in a linear Paul trap. BeH + ions generated by an exothermic reaction between electronically excited Be + ions and residual H 2 in the vacuum chamber are photon-dissociated with two photons scanning over the range of 201 nm to 208 nm. Our experiment provides a novel method to maintain the number of Be + ions stable in a Coulomb crystal with a middle ultraviolet band dissociation laser. This two-photon dissociation method extends the wavelength range of the dissociation laser for BeH + compared to the one-photon dissociation, and the method can be utilized to all alkaline earth atomic ions which require suppression of the reaction with residual H 2 gas in vacuum.

Chinese Physics B•Dec 31, 2024•3 citations

Increase of the barium ion-trap lifetime via photodissociation

Hao Wu, Michael Mills, Elizabeth P. West +2 more

The lifetime of ${\mathrm{Ba}}^{+}$ ions confined in a Paul trap is found, under typical conditions, to be limited by chemical reactions with residual background gas. An integrated ion-trap and time-of-flight mass spectrometer are used to analyze the reactions of the trapped ${\mathrm{Ba}}^{+}$ ions with three common gases in an ultrahigh vacuum system (${\mathrm{H}}_{2}$, ${\mathrm{CO}}_{2}$, and ${\mathrm{H}}_{2}\mathrm{O}$). It is found that the products of these reactions can all be photodissociated by a single ultraviolet laser at 225 nm, thereby allowing the recovery of the ${\mathrm{Ba}}^{+}$ ions and leading to an increase of the effective trap lifetime. For a Coulomb crystal, the lifetime increased from roughly 6 h to 2 days at room temperature. It is suggested that higher enhancement factors are possible in systems with stronger traps. In addition, photodissociation wavelengths for other common trapped-ion systems are provided.

arXiv:2109.05174•Physical Review A•Dec 3, 2021•9 citations

Photodissociation spectra of single trapped CaOH+ molecular ions

Zhenlin Wu, Stefan Walser, Verena Podlesnic +8 more

Molecular ions that are generated by chemical reactions with trapped atomic ions can serve as an accessible testbed for developing molecular quantum technologies. On the other hand, they are also a hindrance to scaling up quantum computers based on atomic ions, as unavoidable reactions with background gases destroy the information carriers. Here, we investigate the single- and two-photon dissociation processes of single CaOH+ molecular ions co-trapped in Ca+ ion crystals using a femtosecond laser system. We report the photodissociation cross section spectra of CaOH+ for single-photon processes at λ = 245-275 nm and for two-photon processes at λ = 500-540 nm. Measurements are interpreted with quantum-chemical calculations, which predict the photodissociation threshold for CaOH+ → Ca+ + OH at 265 nm. This result can serve as a basis for dissociation-based spectroscopy for studying the internal structure of CaOH+. The result also gives a prescription for recycling Ca+ ions in large-scale trapped Ca+ quantum experiments from undesired CaOH+ ions formed in the presence of background water vapor.

arXiv:2401.10854•The Journal of Chemical Physics•Jul 22, 2024•4 citations

Formation of translationally cold MgH + and MgD + molecules in an ion trap

Kristian Speranza Mølhave, Michael Drewsen

We have produced and cooled the molecular ions ${\mathrm{MgH}}^{+}$ and ${\mathrm{MgD}}^{+}$ in a linear Paul trap. These ions were generated by the photochemical reactions ${\mathrm{Mg}}^{+}{(3p}^{2}{P}_{3/2})+{\mathrm{H}}_{2} ({\mathrm{D}}_{2})\ensuremath{\rightarrow}{\mathrm{MgH}}^{+} ({\mathrm{MgD}}^{+})+\mathrm{H} (\mathrm{D}),$ and identified by the radial separation in the trap of ions with different charge-to-mass ratios. The molecular translational motion was cooled sympathetically by Coulomb interaction with laser-cooled ${\mathrm{Mg}}^{+}$ ions to a temperature estimated to be below 100 mK. Ordered structures (ion crystals) containing more than 1000 ions, with more than $95%$ being molecular ions, were obtained. Such translationally cold and well-localized samples of molecular ions could become very useful for molecular physics and chemistry.

Physical Review A•Jun 2, 2000•247 citations

High-fidelity quantum control using ion crystals in a Penning trap

Michael J. Biercuk, Hermann Uys, Aaron P. VanDevender +3 more

We provide an introduction to the use of ion crystals in a Penning trap for experiments in quantum information. Macroscopic Penning traps allow for the containment of a few to a few million atomic ions whose internal states may be used in quantum information experiments. Ions are laser Doppler cooled, and the mutual Coulomb repulsion of the ions leads to the formation of crystalline arrays. The structure and dimensionality of the resulting ion crystals may be tuned using a combination of control laser beams and external potentials. We discuss the use of two-dimensional $^{9}$Be$^{+}$ ion crystals for experimental tests of quantum control techniques. Our primary qubit is the 124 GHz ground-state electron spin flip transition, which we drive using microwaves. An ion crystal represents a spatial ensemble of qubits, but the effects of inhomogeneities across a typical crystal are small, and as such we treat the ensemble as a single effective spin. We are able to initialize the qubits in a simple state and perform a projective measurement on the system. We demonstrate full control of the qubit Bloch vector, performing arbitrary high-fidelity rotations ($\tau_{\pi}\sim$200 $\mu$s). Randomized Benchmarking demonstrates an error per gate (a Pauli-randomized $\pi/2$ and $\pi$ pulse pair) of $8\pm1\times10^{-4}$. Ramsey interferometry and spin-locking measurements are used to elucidate the limits of qubit coherence in the system, yielding a typical free-induction decay coherence time of $T_{2}\sim$2 ms, and a limiting $T_{1\rho}\sim$688 ms. These experimental specifications make ion crystals in a Penning trap ideal candidates for novel experiments in quantum control. As such, we briefly describe recent efforts aimed at studying the error-suppressing capabilities of dynamical decoupling pulse sequences, demonstrating an ability to extend qubit coherence and suppress phase errors. We conclude with a discussion of future avenues for experimental exploration, including the use of additional nuclear-spin-flip transitions for effective multiqubit protocols, and the potential for Coulomb crystals to form a useful testbed for studies of large-scale entanglement.

Quantum Information and Computation•Nov 1, 2009•54 citations
We demonstrate photodissociation of BeH+{\mathrm{BeH}}^{+}BeH+ ions within a Coulomb crystal of thousands of 9Be+{}^{9}{\mathrm{Be}}^{+}9Be+ ions confined in a Penning trap. Because BeH+{\mathrm{BeH}}^{+}BeH+ ions are created via exothermic reactions between trapped, laser-cooled Be+(2P3/2){\mathrm{Be}}^{+}({}^{2}{P}_{3/2})Be+(2P3/2​) and background H2{\mathrm{H}}_{2}H2​ within the vacuum chamber, they represent a major contaminant species responsible for infidelities in large-scale trapped-ion quantum-information experiments. The rotational-state-insensitive dissociation scheme described here makes use of 157-nm photons to produce Be+{\mathrm{Be}}^{+}Be+ and H as products, thereby restoring Be+{\mathrm{Be}}^{+}Be+ ions without the need for reloading. This technique facilitates longer experiment runtimes at a given background H2{\mathrm{H}}_{2}H2​ pressure and may be adapted for removal of MgH+{\mathrm{MgH}}^{+}MgH+ and AlH+{\mathrm{AlH}}^{+}AlH+ impurities.
Trapped Be + ions are a leading platform for quantum information science (Gaebler et al 2016 Phys. Rev. Lett. 117 060505 ), but reactions with background gas species, such as H 2 and H 2 O, result in qubit loss. Our experiment reveals that the BeOH + ion is the final trapped ion species when both H 2 and H 2 O exist in a vacuum system with cold, trapped Be + . The BeH + product in the Be + + H 2 reaction further reacts with H 2 O to form BeOH + . To understand the loss mechanism, low-temperature reactions between sympathetically cooled BeD + ions and H 2 O molecules have been investigated using an integrated, laser-cooled Be + ion trap and high-resolution time-of-flight mass spectrometer (Schneider et al 2014 Phys. Rev. Appl. 2 034013 ). Among all the possible products, BeH 2 O + , H 2 DO + , BeOD + , and BeOH + , only the BeOH + molecular ion was observed experimentally, with the assumed co-product of HD. Theoretical analyses based on explicitly correlated restricted coupled cluster singles, doubles, and perturbative triples (RCCSD(T)-F12) method with the augmented correlation-consistent polarized triple zeta (AVTZ) basis set reveal that two intuitive direct abstraction product channels, Be + H 2 DO + and D + BeH 2 O + , are not energetically accessible at the present reaction temperature (∼150 K). Instead, a double displacement BeOH + + HD product channel is accessible due to a large exothermicity of 1.885 eV through a submerged barrier in the reaction pathway. While the BeOD + + H 2 product channel has a similar exothermicity, the reaction pathway is dynamically unfavourable, as suggested by a sudden vector projection analysis. This work sheds light on the origin of the loss and contaminations of the laser-cooled Be + ions in quantum-information experiments.
Abstract Two-photon dissociation of BeH + ions is studied by detecting the fluorescence changes of Be + –BeH + bi-component Coulomb crystal in a linear Paul trap. BeH + ions generated by an exothermic reaction between electronically excited Be + ions and residual H 2 in the vacuum chamber are photon-dissociated with two photons scanning over the range of 201 nm to 208 nm. Our experiment provides a novel method to maintain the number of Be + ions stable in a Coulomb crystal with a middle ultraviolet band dissociation laser. This two-photon dissociation method extends the wavelength range of the dissociation laser for BeH + compared to the one-photon dissociation, and the method can be utilized to all alkaline earth atomic ions which require suppression of the reaction with residual H 2 gas in vacuum.
The lifetime of Ba+{\mathrm{Ba}}^{+}Ba+ ions confined in a Paul trap is found, under typical conditions, to be limited by chemical reactions with residual background gas. An integrated ion-trap and time-of-flight mass spectrometer are used to analyze the reactions of the trapped Ba+{\mathrm{Ba}}^{+}Ba+ ions with three common gases in an ultrahigh vacuum system (H2{\mathrm{H}}_{2}H2​, CO2{\mathrm{CO}}_{2}CO2​, and H2O{\mathrm{H}}_{2}\mathrm{O}H2​O). It is found that the products of these reactions can all be photodissociated by a single ultraviolet laser at 225 nm, thereby allowing the recovery of the Ba+{\mathrm{Ba}}^{+}Ba+ ions and leading to an increase of the effective trap lifetime. For a Coulomb crystal, the lifetime increased from roughly 6 h to 2 days at room temperature. It is suggested that higher enhancement factors are possible in systems with stronger traps. In addition, photodissociation wavelengths for other common trapped-ion systems are provided.
Molecular ions that are generated by chemical reactions with trapped atomic ions can serve as an accessible testbed for developing molecular quantum technologies. On the other hand, they are also a hindrance to scaling up quantum computers based on atomic ions, as unavoidable reactions with background gases destroy the information carriers. Here, we investigate the single- and two-photon dissociation processes of single CaOH+ molecular ions co-trapped in Ca+ ion crystals using a femtosecond laser system. We report the photodissociation cross section spectra of CaOH+ for single-photon processes at λ = 245-275 nm and for two-photon processes at λ = 500-540 nm. Measurements are interpreted with quantum-chemical calculations, which predict the photodissociation threshold for CaOH+ → Ca+ + OH at 265 nm. This result can serve as a basis for dissociation-based spectroscopy for studying the internal structure of CaOH+. The result also gives a prescription for recycling Ca+ ions in large-scale trapped Ca+ quantum experiments from undesired CaOH+ ions formed in the presence of background water vapor.
We have produced and cooled the molecular ions MgH+{\mathrm{MgH}}^{+}MgH+ and MgD+{\mathrm{MgD}}^{+}MgD+ in a linear Paul trap. These ions were generated by the photochemical reactions ${\mathrm{Mg}}^{+}{(3p}^{2}{P}_{3/2})+{\mathrm{H}}_{2} ({\mathrm{D}}_{2})\ensuremath{\rightarrow}{\mathrm{MgH}}^{+} ({\mathrm{MgD}}^{+})+\mathrm{H} (\mathrm{D}),$ and identified by the radial separation in the trap of ions with different charge-to-mass ratios. The molecular translational motion was cooled sympathetically by Coulomb interaction with laser-cooled Mg+{\mathrm{Mg}}^{+}Mg+ ions to a temperature estimated to be below 100 mK. Ordered structures (ion crystals) containing more than 1000 ions, with more than 9595%95 being molecular ions, were obtained. Such translationally cold and well-localized samples of molecular ions could become very useful for molecular physics and chemistry.
We provide an introduction to the use of ion crystals in a Penning trap for experiments in quantum information. Macroscopic Penning traps allow for the containment of a few to a few million atomic ions whose internal states may be used in quantum information experiments. Ions are laser Doppler cooled, and the mutual Coulomb repulsion of the ions leads to the formation of crystalline arrays. The structure and dimensionality of the resulting ion crystals may be tuned using a combination of control laser beams and external potentials. We discuss the use of two-dimensional 9^{9}9Be+^{+}+ ion crystals for experimental tests of quantum control techniques. Our primary qubit is the 124 GHz ground-state electron spin flip transition, which we drive using microwaves. An ion crystal represents a spatial ensemble of qubits, but the effects of inhomogeneities across a typical crystal are small, and as such we treat the ensemble as a single effective spin. We are able to initialize the qubits in a simple state and perform a projective measurement on the system. We demonstrate full control of the qubit Bloch vector, performing arbitrary high-fidelity rotations ($\tau_{\pi}\sim$200 μ\muμs). Randomized Benchmarking demonstrates an error per gate (a Pauli-randomized π/2\pi/2π/2 and π\piπ pulse pair) of 8±1×10−48\pm1\times10^{-4}8±1×10−4. Ramsey interferometry and spin-locking measurements are used to elucidate the limits of qubit coherence in the system, yielding a typical free-induction decay coherence time of $T_{2}\sim$2 ms, and a limiting $T_{1\rho}\sim$688 ms. These experimental specifications make ion crystals in a Penning trap ideal candidates for novel experiments in quantum control. As such, we briefly describe recent efforts aimed at studying the error-suppressing capabilities of dynamical decoupling pulse sequences, demonstrating an ability to extend qubit coherence and suppress phase errors. We conclude with a discussion of future avenues for experimental exploration, including the use of additional nuclear-spin-flip transitions for effective multiqubit protocols, and the potential for Coulomb crystals to form a useful testbed for studies of large-scale entanglement.