41 research outputs found
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 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
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 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
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
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 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) 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 level per second, limited by the lock transfer
properties and the frequency stability of the AOM control synthesizer
Experimental Demonstration of a Terahertz Frequency Reference based on Coherent Population Trapping
A novel protocol of interrogation based on coherent population trapping in an
N-level scheme atomic system leads to dark resonances involving three different
photons. An ensemble of several hundreds of radiofrequency-trapped ions is
probed by three lasers simultaneously locked onto the same optical frequency
comb, resulting in high-contrast spectral lines referenced to an atomic
transition in the THz domain. We discuss the cause of uncertainties and
limitations for this method and show that reaching a sub-kHz resolution is
experimentally accessible via this interrogation protocole
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
An analytical approach to symmetry breaking in multipole RF-traps
Radio-frequency linear multipole traps have been shown to be very sensitive
to mis-positioning of their electrodes, which results in a symmetry breaking
and leads to extra local minima in the trapping potential \cite{pedregosa17}
disturbing the operation of the trap. In this work, we analytically describe
the RF-potential of a realistic octupole trap by including lower order terms to
the well-established equation for a perfectly symmetric octupole trap. We
describe the geometry by a combination of identified defects, characterised by
simple analytical expressions. A complete equation is proposed for a trap with
any electrode deviation relying on a combination of the simple cases where the
defects are taken individually. Our approach is validated by comparison between
analytical and numerical results for defect sizes up to 4\% of the trap radius.
As described in \cite{pedregosa18}, an independent fine-tuning of the amplitude
of the RF voltage applied on each electrode can be used to mitigate the
geometrical defects of a realistic trap. In a different way than in
\cite{pedregosa18}, the knowledge of an analytical equation for the potential
allows to design the set of RF-voltages required for this compensation, based
on the experimental measurement of the ion position in the trap, without
information concerning the exact position of each electrode, and with a small
number of iterations. The requirements, performances and limitations of this
protocol are discussed via comparison of numerical simulations and analytical
results.Comment: Accepted manuscript by quantum Science and TEchnology :
https://iopscience.iop.org/article/10.1088/2058-9565/abeaf