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We present a new robust decoupling scheme suitable for levels with either half-integer or integer angular momentum states. Through continuous dynamical decoupling techniques, we create a protected qubit subspace, utilizing a multistate qubit construction. Remarkably, the multistate system can also be composed of multiple substates within a single level. Our scheme can be realized with state-of-the-art experimental setups and thus has immediate applications for quantum information science. While the scheme is general and relevant for a multitude of solid-state and atomic systems, we analyze its performance for the case composed of trapped ions. Explicitly, we show how single qubit gates and an ensemble coupling to a cavity mode can be implemented efficiently. The scheme predicts a coherence time of ~1 s, as compared to typically a few milliseconds for the bare states. [ABSTRACT FROM AUTHOR]

A general method for rotational microwave spectroscopy and control of polar molecular ions via direct microwave addressing is considered. Our method makes use of spatially varying ac Stark shifts, induced by far off-resonant, focused laser beams to achieve an effective coupling between the rotational state of a molecular ion and the electronic state of an atomic ion. In this setting, the atomic ion is used for read-out of the molecular ion state, in a manner analogous to quantum logic spectroscopy based on Raman transitions. In addition to high-precision spectroscopy, this setting allows for rotational ground state cooling, and can be considered as a candidate for the quantum information processing with polar molecular ions. All elements of our proposal can be realized with currently available technology. [ABSTRACT FROM AUTHOR]

Storage and cooling of highly charged ions require ultra-high vacuum levels obtainable by means of cryogenic methods. We have developed a linear Paul trap operating at 4 K capable of very long ion storage times of about 30 h. A conservative upper bound of the H2 partial pressure of about 10-15 mbar (at 4 K) is obtained from this. External ion injection is possible and optimized optical access for lasers is provided, while exposure to black body radiation is minimized. First results of its operation with atomic and molecular ions are presented. An all-solid state laser system at 313 nm has been set up to provide cold Be+ ions for sympathetic cooling of highly charged ions. [ABSTRACT FROM AUTHOR]

We report on the loading of large ion Coulomb crystals into a linear Paul trap incorporating a high-finesse optical cavity (ℱ∼3000). We show that, even though the 3-mm diameter dielectric cavity mirrors are placed between the trap electrodes and separated by only 12 mm, it is possible to produce in situ ion Coulomb crystals containing more than 105 calcium ions of various isotopes and with lengths of up to several millimeters along the cavity axis. We show that the number of ions inside the cavity mode is, in principle, high enough to achieve strong collective coupling between the ion Coulomb crystal and the cavity field. The results thus represent an important step towards ion trap based Cavity Quantum ElectroDynamics (CQED) experiments using cold ion Coulomb crystals. [ABSTRACT FROM AUTHOR]

Ion processes can be studied by a wide variety of experimental setups ranging from small ion trap devises to large storage rings. In Penning as well as Paul (rf) traps, the effective oscillation frequencies of trapped particles have, e.g., extensively been used to gain information of the charge to mass ratio of produced atomic and molecular ions. For such investigations, space charges due to the simultaneous presence of multiple ions, is a limiting factor, and hence low density or single particle experiments are preferred. The purpose of the present article is to discuss the prospects of using traps in the opposite regime where space charges dominate and so-called ion Coulomb crystals form (at temperatures about ∼10 mK). The experimental results presented below show that in this regime, differences in single particle oscillation frequencies of simultaneously trapped ions lead to a spatial segregation of the ion species which can be used as means to study a large variety of ion processes. Since the detection relies generally on observations of changes in the spatial structure of the Coulomb crystals formed by the cold, trapped ions, it can often be non-destructive, i.e., the product ions of a certain process will stay trapped and be available for further experimentations. It is the intention of the present article to discuss, via some examples, the usefulness of ion Coulomb crystals as a tool in investigations of ion processes more than it is the aim to provide new data. [Copyright &y& Elsevier]

Investigates the role of effective temperature and its relevance to ordering phenomena and radio frequency heating. Confinement of charged particles in a high-frequency quadrupole electric field; Use of radio frequency traps; Coupling between the kinetic energy in the periodic motion of trapped ions into aperiodic, thermal motion.

We briefly discuss some possibilities for cooling, identification and spectroscopy of super-heavy element (SHE) ions based on recent results obtained from studies of atomic and molecular ions in linear rf traps. Since these investigations only relied on the charge and the mass of the ion of interest, we believe it should be straight forward to adopt most of the techniques for SHE ion research. [ABSTRACT FROM AUTHOR]

Control over the motional degrees of freedom of atoms, ions, and molecules in a field-free environment enables unrivalled measurement accuracies but has yet to be applied to highly charged ions (HCIs), which are of particular interest to future atomic clock designs and searches for physics beyond the Standard Model. Here, we report on the Coulomb crystallization of HCIs (specifically 40Ar13+) produced in an electron beam ion trap and retrapped in a cryogenic linear radiofrequency trap by means of sympathetic motional cooling through Coulomb interaction with a directly laser-cooled ensemble of Be+ ions.We also demonstrate cooling of a single Ar13+ ion by a single Be+ ion --the prerequisite for quantumlogic spectroscopy with a potential 10-19 accuracy level. Achieving a seven-orders-of-magnitude decrease in HCI temperature starting at megakelvin down to the millikelvin range removes the major obstacle for HCI investigation with high-precision laser spectroscopy. [ABSTRACT FROM AUTHOR]

We present a method to measure the decay rate of the first excited vibrational state of polar molecular ions that are part of a Coulomb crystal in a cryogenic linear Paul trap. Specifically, we have monitored the decay of the ∣ν=1,J=1⟩X towards the ∣ν=0,J=0⟩X level in MgH+ by saturated laser excitation of the ∣ν=0,J=2⟩X-∣ν=1,J=1⟩X transition followed by state selective resonance enhanced two-photon dissociation out of the ∣ν=0,J=2⟩X level. The experimentally observed rate of 6.32(0.69)  s-1 is in excellent agreement with the theory value of 6.13(0.03)  s-1 (this Letter). The technique enables the determination of decay rates, and thus absorption strengths, with an accuracy at the few percent level. [ABSTRACT FROM AUTHOR]