R. C. Thompson

High-resolution measurements of isotope shifts and hyperfine structure in stable and radioactive lead isotopes

The authors present new measurements of isotopic shifts and hyperfine structure in the lead resonance line for a total of 15 isotopes. The experimental accuracy is of order 4 MHz. Using independent measurements of the nuclear parameter lambda for the stable isotopes they have derived lambda for all measured isotopes. The derived values of lambda are compared with various theoretical predictions for the lead nuclei. The authors also give values for the nuclear magnetic dipole and electric quadrupole moments deduced from the measurements.

Ion Oscillation Frequencies in a Combined Trap

Abstract A combined trap is a quadrupole trap to which the fields of both the Paul and the Penning traps are applied. In this paper, equations of motion for ions confined in a combined trap are derived from first principles. The equations of motion are shown to give well-understood solutions for the Paul and Penning traps in the appropriate cases before they are solved to yield the axial and radial oscillation frequencies for ions in a combined trap. The dependence of these oscillation frequencies on the applied fields is investigated.

Spectroscopy of Trapped Ions

Publisher Summary This chapter reviews the recent progress made in the use of trapped ions for spectroscopy, quantum optics, and frequency standards. It is clear that techniques using trapped ions are complementary to other spectroscopic techniques, offering significant advantages under some circumstances, but not necessarily all. In particular, ion traps have made a significant impact in the areas of precision measurements of various sorts; the studies of isolated atomic systems; and the investigations of different aspects of quantum mechanics and quantum optics. They are beginning to be used with small amounts of rare isotopes, but the loading efficiency needs to be improved significantly to further their impact. The prospects are still high for their use in the next generation of frequency standards, particularly in the microwave region in the near future. Optical frequency standards may have to wait a little longer. However, new applications are emerging and ion traps will, therefore, continue to have a dramatic impact on spectroscopy and related areas of science.

Current perspectives on the physics of trapped ions

Abstract This paper presents a survey of recent work in the field of the physics of trapped ions, as an introduction to this Journal of Modern Optics special issue. The contrasting properties of trapped ion clouds and the single trapped ion are highlighted, together with their application to frequency standards and fundamental measurements.

Double well potentials and quantum phase transitions in ion traps.

We demonstrate that the radial degree of freedom of strings of trapped ions in the quantum regime may be prepared and controlled accurately through the variation of the external trapping potential while at the same time its properties are measurable with high spatial and temporal resolution. This provides a new testbed giving access to static and dynamical properties of the physics of quantum-many-body systems and quantum phase transitions that are hard to simulate on classical computers. Furthermore, it allows for the creation of double well potentials with experimentally accessible tunneling rates, with applications in testing the foundations of quantum physics and precision sensing.

Precision measurement aspects of ion traps

The use of ion traps in precision measurements of various kinds has been growing rapidly in recent years. This review attempts to survey work in this area. It starts with a brief description of the two main types of ion traps and how they work, and discusses the different methods available for detection of ions in a trap and for reducing their kinetic energy. The main part of the review deals with measurements of the magnetic moments (g-factors) of electrons, positrons and ions in traps; precision mass determinations, especially for rare isotopes produced in small quantities; and measurements of microwave and optical transition frequencies in ions, especially with applications to frequency standards in mind. The review concludes with a very brief sketch of some of the other main uses of ion traps to date, touching on the study of quantum jumps and ion crystals, and the measurement of the lifetimes of excited electronic states of ions

Quantum State Diffusion Theory and a Quantum Jump Experiment

We use a recent stochastical diffusion model of quantum evolution to represent the evolution of a three-level quantum system undergoing quantum jumps. This is possible because the continuous change in the quantum state in this diffusion model is so rapid that it appears to be instantaneous in comparison with the time between transitions. Experimental data from a study of the intermittent fluorescence of a single trapped 24Mg+ ion and equivalent theoretical data are shown to be strikingly similar. Statistical comparisons of the data are also made.

Proposed precision laser spectrometer for trapped, highly charged ions

We propose a type of precision laser spectrometer for trapped, highly charged ions nearly at rest. It consists of a cylindrical, open-endcap Penning trap in which an externally produced bunch of highly charged ions can be confined and investigated by means of laser spectroscopy. The combination of confinement, cooling, and compression of a dense ion cloud will allow the ground-state hyperfine splitting in highly charged ions to be measured with an accuracy three orders of magnitude better than in any previous experiment. A systematic study of different charge states and different isotopes of the same element allows for highly sensitive tests of bound-state quantum electrodynamics and for a precision determination of nuclear properties. Apart from stable isotopes, radioactive species with half-lives longer than about 1 hour also can be investigated.

Monolithic microfabricated ion trap chip design for scaleable quantum processors

A design is proposed for a novel ion trap quantum processor chip, microfabricated using a process based on planar silica-on-silicon techniques. The trap electrodes are of gold-coated silica and are spaced by highly doped silicon in a monolithic structure. This design allows a unit aspect-ratio trap with an ion-electrode separation below 100 μm, when using current fabrication techniques. The trapping potential is modelled and the operating parameters required to achieve motional frequencies of a few MHz are calculated. RF loss and the resultant heating of the trap chip are not found to be a factor limiting the traps operation. This monolithic unit aspect-ratio trap is therefore expected to exhibit a deep potential well, high trap efficiency, and a low RF loss, when compared to other microfabricated traps. This technological approach is in principle scaleable to complex devices, and may form the basis for large-scale ion trap quantum processors.

Fundamental physics with trapped ions

Ion traps allow us to study single quantum systems, cooled to the lowest vibrational state of motion within confining electric and magnetic fields. In this article, we describe the working principles of ion traps and the methods used to cool the ions (principally laser cooling). We then discuss how these cold ions, held almost at rest in the trap, can be used to illuminate fundamental issues of quantum mechanics: quantum jumps, the quantum Zeno effect and the quantum statistics of photons scattered by the ions. Finally, we describe how several ions loaded in a trap are cooled into ordered quasi crystals.