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Mortensen, Anders; Lindballe, J. J. T.; Jensen, Inger S.; Staanum, Peter; Voigt, D.; Drewsen, Michael

doi:10.1103/physreva.69.042502

Cited by 51 publications

(35 citation statements)

References 18 publications

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“…The 40 Ca + ions are produced isotope-selectively by resonance-enhanced photo-ionization of atoms from an effusive beam of naturally abundant calcium [26,27]. Doppler laser cooling is achieved along the trap center axis by using counter propagating laser beams tuned to the 4S 1/2 -4P 1/2 transition at 397 nm and with a repumper beam on the 3D 3/2 -4P 1/2 transition at 866 nm.…”

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confidence: 99%

Observation of Three-Dimensional Long-Range Order in Small Ion Coulomb Crystals in an rf Trap

et al. 2006

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Three-dimensional long-range ordered structures in smaller and near-spherically symmetric Coulomb crystals of 40 Ca + ions confined in a linear rf Paul trap have been observed when the number of ions exceeds ∼1000 ions. This result is unexpected from ground state molecular dynamics (MD) simulations, but found to be in agreement with MD simulations of metastable ion configurations. Previously, three-dimensional long-range ordered structures have only been reported in Penning traps in systems of ∼50,000 ions or more. [3,4,5,6,7,8,9,10,11] and most recently dusty plasmas [12]. In nature, Coulomb crystals are presently expected to exist in exotic dense astrophysical objects [13].Theoretically, it has been found that the thermodynamic properties of infinite OCPs of a single species, are fully characterized by the coupling parameter [14]where Q is the charge of the particles, a ws is the Wigner Seitz radius defined from the zero temperature particle density n 0 by 4πa 3 ws /3 = 1/n 0 . Furthermore, a liquidsolid transition to a body centered cubic (bcc) structure is expected to occur for Γ ∼ 170 [15,16]. For finite OCPs simulations have shown that the situation is more complex, and the properties will depend both on the size and shape of the ion plasma, since surface effects cannot be neglected [17,18,19,20,21].Ion Coulomb crystals, which for more than a decade have been realized with laser-cooled ion plasmas confined by electromagnetic fields in Penning traps [4,5,9] or in radio-frequency (rf) traps [3,6,7,8,10], offer an excellent opportunity to study finite size effects of OCPs under various conditions. The Coulomb crystal structures studied range from one-dimensional (1D) long cylindrical crystals [3,6,7,8] over 2D thin planar crystals [4] to 3D spheroidal crystals [4,5,6,9]. The 3D spheroidal ion Coulomb crystals reported in Refs. [6,7] are composed of concentric ion shells formed under the influence of the surface of the Coulomb crystals. Simulations indicate that the ions form a near-2D hexagonal short-range ordered structure within each shell [18]. Similarly, shell and short-range order have recently been observed in dusty plasma experiments [12].Observations of three-dimensional long-range order in Coulomb crystals have previously only been reported in the case of ∼50,000 or more laser-cooled ions in a Penning trap [4,5,9]. In contrast to Penning traps, in rf traps Coulomb crystals undergo strong quadrupole deformations at the frequency of the applied rf field due to the so-called micro-motion [22] of the ions. Since this motion is known to produce heating [22,23], it has not been obvious that three-dimensional long-range order could be obtained in such traps.In this Letter, we present observations of long-range structure in Coulomb crystals of 40 Ca + ions confined in a linear rf Paul trap. By varying the number of ions in near-spherically symmetric crystals, we have shown that bcc structures indeed can be observed in such traps even with the number of ions being below a thousand.The linear Paul trap used i...

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Observation of Three-Dimensional Long-Range Order in Small Ion Coulomb Crystals in an rf Trap

et al. 2006

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“…The 40 Ca + ions are produced through isotope selective photoionization of atoms in a beam of natural abundant calcium [26,28]. The Coulomb crystals are created through Doppler laser-cooling along the trap axis by two counter-propagating beams at 397 nm (total power of ∼ 4 mW and beam diameter of ∼ 1 mm) and an 866 nm beam applied from the side to prevent the ions from being shelved into the D 3/2 state (see insert of Fig.…”

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confidence: 99%

Noninvasive Vibrational Mode Spectroscopy of Ion Coulomb Crystals through Resonant Collective Coupling to an Optical Cavity Field

et al. 2010

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We report on a novel non-invasive method to determine the normal mode frequencies of ion Coulomb crystals in traps based on the resonance enhanced collective coupling between the electronic states of the ions and an optical cavity field at the single photon level. Excitations of the normal modes are observed through a Doppler broadening of the resonance. An excellent agreement with the predictions of a zero-temperature uniformly charged liquid plasma model is found. The technique opens up for investigations of the heating and damping of cold plasma modes, as well as the coupling between them.PACS numbers: 37.30.+i,52.27.Gr,37.10. Vz,52.27.Jt,42.50.Pq Cold one-component plasma physics [1] has in the past two decades led to a series of interesting results due to the availability of fast computers [2][3][4][5] as well as the possibility to experiment with ensembles of trapped, lasercooled atomic ions [6][7][8][9][10][11][12][13][14][15][16]. Prominent examples are the understanding of structural properties of crystallized cold plasmas in both Penning [6,7] and Paul [8-10, 15, 16] traps, and the investigation of the normal mode dynamics of cold magnetized plasmas in Penning traps [11][12][13][14]. While there exist many similarities between experiments in Penning and Paul traps, the unmagnetized plasmas in Paul traps are e.g. known to heat up much faster than the magnetized plasmas in Penning traps due to the presence of the rf fields [3,17]. The lack of a rotational symmetry axis in Paul traps has as well been found to be responsible for the observation of specific crystalline structures [16]. Exploration of the normal mode dynamics of unmagnetized ion Coulomb crystals in e.g. linear Paul traps will hence add to our understanding of the influence of the trapping environment on the physics of such crystals. Furthermore, since large Coulomb crystals are excellent candidates for the realization of high-fidelity quantum memories for light [18], such studies can shed light on the influence of the excitation of these modes on the fidelity as well as on the prospect of storing several photonic quantum bits through deliberate excitations of specific vibrational modes. Larger Coulomb crystals have as well recently been considered as a system for performing quantum simulations, in which respect knowledge of normal mode dynamics is needed [19]. Finally, ion Coulomb crystals represent extremely interesting systems to study cavity optomechanics phenomena [20,21], since, in spite of their solid nature, they possess free atomic resonance properties and can hence be made very sensitive to the radiation pressure force exerted by optical fields.In this Letter, we report on the study of normal mode vibrations of Coulomb crystals of 40 Ca + ions in a linear Paul trap by a novel non-invasive technique. The technique is based on monitoring the coherent collective resonant response of the atomic ions constituting the crystal to a single photon optical cavity field [18]. By having a standing wave optical cavity incorporated in the tr...

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“…The first step in this process is a resonant transition and hence is isotope selective. The relevant energy levels are shown on figure 8 and full details can be found in [10,16]. The 272nm light is generated by frequency-quadrupling light from a fibre laser at 1088nm [21].…”

Section: Experimental Techniquesmentioning

confidence: 99%

“…These ions are laser cooled on the rapid S 1/2 −→ P 1/2 dipole transition at 397nm. A repumper at 866nm is required in order to prevent build up of population in the metastable D 3/2 state [16]. Ions are detected by imaging the spontaneously re-emitted 397nm light onto an image intensifier, the output of which is monitored with a CCD camera.…”

Section: Experimental Techniquesmentioning

confidence: 99%

An all-optical ion-loading technique for scalable microtrap architectures

et al. 2007

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An experimental demonstration of a novel all-optical technique for loading ion traps, that has particular application to microtrap architectures, is presented. The technique is based on photo-ionisation of an atomic beam created by pulsed laser ablation of a calcium target, and provides improved temporal control compared to traditional trap loading methods. Ion loading rates as high as 125 ions per second have so far been observed. Also described are observations of trap loading where Rydberg state atoms are photo-ionised by the ion Doppler cooling laser.

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Isotope shifts of the4s2S01→4s5pP1

Abstract: Isotope shifts of the 4s 2 1 S 0 → 4s5p 1 P 1 transition and hyperfine splitting of the

Cited by 51 publications

References 18 publications

Observation of Three-Dimensional Long-Range Order in Small Ion Coulomb Crystals in an rf Trap

Observation of Three-Dimensional Long-Range Order in Small Ion Coulomb Crystals in an rf Trap

Noninvasive Vibrational Mode Spectroscopy of Ion Coulomb Crystals through Resonant Collective Coupling to an Optical Cavity Field

An all-optical ion-loading technique for scalable microtrap architectures

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