Detection Techniques for Trapped Ions

Various techniques are used to detect the presence of charged particles stored in electromagnetic traps, their energy, their mass, or their internal states. Detection methods can rely on the variation of the number of trapped particles (destructive methods) or the use of the ion's interaction with electromagnetic radiation as a non-destructive tool to probe the trapped particles. This review gives an introduction into various methods, discussing the basic mode of operation completed by the description of recent realizations

Ion transport in macroscopic RF linear traps

Efficient transport of cold atoms or ions is a subject of increasing concern in many experimental applications reaching from quantum information processing to frequency metrology. For the scalable quantum computer architectures based on the shuttling of individual ions, different transport schemes have been developed, which allow to move single atoms minimizing their energy gain. In this article we discuss the experimental implementation of the transport of a three-dimensional ion cloud in a macroscopic linear radiofrequency (RF) trap. The present work is based on numerical simulations done by molecular dynamics taking into account a realistic experimental environment. The deformation of the trapping potential and the spatial extension of the cloud during transport appears to be the major source of the ion energy gain. The efficiency of transport in terms of transfer probability and ion number is also discussed

Comment on "Prospect of optical frequency standard based on a 43Ca+ ion"

A recent evaluation of the frequency uncertainty expected for an optical frequency standard based on a single trapped $^{43}$Ca$^+$ ion was published in Phys. Rev. A {\bf 72} (2005) 043404. The paper contains some interesting information like systematic frequency shifts but fails to depict their uncertainty, leading to confuse accuracy and precision. The conclusions about the major contribution to the frequency shift are not consistent with the presented calculations and omit comparisons with data published previously

A double ion trap for large Coulomb crystals

While the linear radiofrequency trap finds various applications in high-precision spectroscopy and quantum information, its higher-order cousin, the linear multipole trap, is almost exclusively employed in physical chemistry. Recently, first experiments have shown interesting features by laser-cooling multipole-trapped ion clouds. Multipole traps show a flatter potential in their centre and therefore a modified density distribution compared to quadrupole traps. Micromotion is an important issue and will certainly influence the dynamics of crystallized ion structures. Our experiment tends to investigate possible crystallization processes in the multipole. In a more general way, we are interested in the study of the dynamics and thermodynamics of large ion clouds in traps of different geometry.Comment: 10th International Workshop on Non-Neutral Plasmas, Greifswald : Germany (2012

Fast and efficient transport of large ion clouds

The manipulation of trapped charged particles by electric fields is an accurate, robust and reliable technique for many applications or experiments in high-precision spectroscopy. The transfer of the ion sample between multiple traps allows the use of a tailored environment in quantum information, cold chemistry, or frequency metrology experiments. In this article, we experimentally study the transport of ion clouds of up to 50 000 ions. The design of the trap makes ions very sensitive to any mismatch between the assumed electric potential and the actual local one. Nevertheless, we show that being fast (100 $\mu$s to transfer over more than 20 mm) increases the transport efficiency to values higher than 90 %, even with a large number of ions. For clouds of less than 2000 ions, a 100 % transfer efficiency is observed

Long-term stabilization of the length of an optical reference cavity

To obtain a high degree of long-term length stabilisation of an optical reference cavity, its free-spectral range is locked by means of an accurate and stable frequency synthesizer. The locking scheme is twofold: a laser is locked on the N$^{th}$ mode of a reference Fabry-Perot cavity and part of the laser light is shifted in frequency to be in resonance with the (N+1)$^{th}$ mode of the cavity. This shift is generated by an acousto-optical modulator (AOM) mounted in a double-pass scheme, matching half of the free spectral range of the reference cavity. The resulting absolute stabilization of the length of the cavity reaches the 10$^{-11}$ level per second, limited by the lock transfer properties and the frequency stability of the AOM control synthesizer

Metastable level lifetimes from electron-shelving measurements with ion clouds and single ions

The lifetime of the 3d^2D_5/2-level in singly-ionized calcium has been measured by the electron-shelving technique on different samples of rf trapped ions. The metastable state has been directly populated by exciting the dipole-forbidden 4S_1/2 - 3D_5/2 transition. In ion clouds, the natural lifetime of this metastable level has been measured to be (1095+-27) ms. For the single-ion case, we determined a lifetime of (1152+-20) ms. The 1sigma-error bars at the 2%-level have different origins for the two kinds of experiments: data fitting methods for lifetime measurements in an ion cloud and control of experimental parameters for a single ion. De-shelving effects are extensively discussed. The influence of differing approaches for the processing of the single-ion quantum jump data on the lifetime values is shown. Comparison with recent measurements shows excellent agreement when evaluated from a given method

Anharmonic contributions in real RF linear quadrupole traps

See also erratum at : http://www.sciencedirect.com/science/article/pii/S1387380610001004International audienceThe radiofrequency quadrupole linear ion trap is a widely used device in physics and chemistry. When used for trapping of large ion clouds, the presence of anharmonic terms in the radiofrequency potential limits the total number of stored ions. In this paper, we have studied the anharmonic content of the trapping potential for different implementations of a quadrupole trap, searching for the geometry best suited for the trapping of large ion clouds. This is done by calculating the potential of a real trap using SIMION8.0, followed by a fit, which allows us to obtain the evolution of anharmonic terms for a large part of the inner volume of the trap

Noise characterization of an Optical Frequency Comb using Offline Cross-Correlation

Using an offline cross-correlation technique, we have analyzed the noise behavior of a new type of optical frequency comb (OFC), which is carrier envelope offset (CEO) free by configuration, due to difference frequency generation. In order to evaluate the instrument's ultimate noise floor, the phase and amplitude noise of a stabilized OFC are measured simultaneously using two analog-to-digital converters. Carrier recovery and phase detection are done by post-processing, eliminating the need for external phase-locked loops and complex calibration techniques. In order to adapt the measurement noise floor and the number of averages used in cross correlation, an adaptive frequency resolution for noise measurement is applied. Phase noise results are in excellent agreement with measurements of the fluctuations of the repetition frequency of the OFC obtained from optical signal