130 research outputs found
Minimizing the Dick Effect in an Optical Lattice Clock
We discuss the minimization of the Dick effect in an optical lattice clock.
We show that optimizing the time sequence of operation of the clock can lead to
a significant reduction of the clock stability degradation by the frequency
noise of the interrogation laser. By using a non-destructive detection of the
atoms, we are able to recycle most of the atoms between cycles and consequently
to strongly reduce the time spent capturing the atoms in each cycle. With
optimized parameters, we expect a fractional Allan deviation better than
2E-16 for the lattice clock.Comment: 6 pages, 10 figures. Submitted to IEEE Transactions on Ultrasonics,
Ferroelectrics, and Frequency Contro
A noise-immune cavity-assisted non-destructive detection for an optical lattice clock in the quantum regime
We present and implement a non-destructive detection scheme for the
transition probability readout of an optical lattice clock. The scheme relies
on a differential heterodyne measurement of the dispersive properties of
lattice-trapped atoms enhanced by a high finesse cavity. By design, this scheme
offers a 1st order rejection of the technical noise sources, an enhanced
signal-to-noise ratio, and an homogeneous atom-cavity coupling. We
theoretically show that this scheme is optimal with respect to the photon shot
noise limit. We experimentally realize this detection scheme in an operational
strontium optical lattice clock. The resolution is on the order of a few atoms
with a photon scattering rate low enough to keep the atoms trapped after
detection. This scheme opens the door to various different interrogations
protocols, which reduce the frequency instability, including atom recycling,
zero-dead time clocks with a fast repetition rate, and sub quantum projection
noise frequency stability
Polarizabilities of the 87Sr Clock Transition
In this paper, we propose an in-depth review of the vector and tensor
polarizabilities of the two energy levels of the 87Sr clock transition whose
measurement was reported in [P. G. Westergaard et al., Phys. Rev. Lett. 106,
210801 (2011)]. We conduct a theoretical calculation that reproduces the
measured coefficients. In addition, we detail the experimental conditions used
for their measurement in two Sr optical lattice clocks, and exhibit the
quadratic behaviour of the vector and tensor shifts with the depth of the
trapping potential and evaluate their impact on the accuracy of the clock
Experimental implementation of non-Gaussian attacks on a continuous-variable quantum key distribution system
An intercept-resend attack on a continuous-variable quantum-key-distribution
protocol is investigated experimentally. By varying the interception fraction,
one can implement a family of attacks where the eavesdropper totally controls
the channel parameters. In general, such attacks add excess noise in the
channel, and may also result in non-Gaussian output distributions. We implement
and characterize the measurements needed to detect these attacks, and evaluate
experimentally the information rates available to the legitimate users and the
eavesdropper. The results are consistent with the optimality of Gaussian
attacks resulting from the security proofs.Comment: 4 pages, 5 figure
Search for vector dark matter in microwave cavities with Rydberg atoms
We propose a novel experiment to search for dark matter, based on the
application of an electric field inside a microwave cavity and electrometry
using Rydberg atoms. We show that this kind of experiment could be extremely
useful for detecting specific dark matter candidates, namely massive vector
fields coupled to the photon field, more commonly known as dark photons. Such a
massive vector field is a good candidate for dark matter. Using realistic
experimental parameters we show that such an experiment could improve the
current constraint on the coupling constant of the dark photons to Standard
Model photons in the 1 to 10~eV mass range, with the possibility of tuning
the maximum sensitivity via the cavity size. The main limiting factors on the
sensitivity of the experiment are the amplitude stability of the applied field
and the measurement uncertainty of the electric field by the atoms.Comment: 14 pages, 4 figure
Atomic fountains and optical clocks at SYRTE: status and perspectives
In this article, we report on the work done with the LNE-SYRTE atomic clock
ensemble during the last 10 years. We cover progress made in atomic fountains
and in their application to timekeeping. We also cover the development of
optical lattice clocks based on strontium and on mercury. We report on tests of
fundamental physical laws made with these highly accurate atomic clocks. We
also report on work relevant to a future possible redefinition of the SI
second
Ultrastable lasers based on vibration insensitive cavities
We present two ultra-stable lasers based on two vibration insensitive cavity
designs, one with vertical optical axis geometry, the other horizontal.
Ultra-stable cavities are constructed with fused silica mirror substrates,
shown to decrease the thermal noise limit, in order to improve the frequency
stability over previous designs. Vibration sensitivity components measured are
equal to or better than 1.5e-11 per m.s^-2 for each spatial direction, which
shows significant improvement over previous studies. We have tested the very
low dependence on the position of the cavity support points, in order to
establish that our designs eliminate the need for fine tuning to achieve
extremely low vibration sensitivity. Relative frequency measurements show that
at least one of the stabilized lasers has a stability better than 5.6e-16 at 1
second, which is the best result obtained for this length of cavity.Comment: 8 pages 12 figure
Experimenting an optical second with strontium lattice clocks
Progress in realizing the SI second had multiple technological impacts and
enabled to further constraint theoretical models in fundamental physics.
Caesium microwave fountains, realizing best the second according to its current
definition with a relative uncertainty of 2-4x10^(-16), have already been
superseded by atomic clocks referenced to an optical transition, both more
stable and more accurate. Are we ready for a new definition of the second? Here
we present an important step in this direction: our system of five clocks
connects with an unprecedented consistency the optical and the microwave
worlds. For the first time, two state-of-the-art strontium optical lattice
clocks are proven to agree within their accuracy budget, with a total
uncertainty of 1.6x10^(-16). Their comparison with three independent caesium
fountains shows a degree of reproducibility henceforth solely limited at the
level of 3.1x10^(-16) by the best realizations of the microwave-defined second.Comment: 9 pages, 4 figures, 2 table
Development of a strontium optical lattice clock for the SOC mission on the ISS
The ESA mission "Space Optical Clock" project aims at operating an optical
lattice clock on the ISS in approximately 2023. The scientific goals of the
mission are to perform tests of fundamental physics, to enable space-assisted
relativistic geodesy and to intercompare optical clocks on the ground using
microwave and optical links. The performance goal of the space clock is less
than uncertainty and
instability. Within an EU-FP7-funded project, a strontium optical lattice clock
demonstrator has been developed. Goal performances are instability below and fractional inaccuracy .
For the design of the clock, techniques and approaches suitable for later space
application are used, such as modular design, diode lasers, low power
consumption subunits, and compact dimensions. The Sr clock apparatus is fully
operational, and the clock transition in Sr was observed with linewidth
as small as 9 Hz.Comment: 12 pages, 8 figures, SPIE Photonics Europe 201
Development of a strontium optical lattice clock for the SOC mission on the ISS
Ultra-precise optical clocks in space will allow new studies in fundamental
physics and astronomy. Within an European Space Agency (ESA) program, the Space
Optical Clocks (SOC) project aims to install and to operate an optical lattice
clock on the International Space Station (ISS) towards the end of this decade.
It would be a natural follow-on to the ACES mission, improving its performance
by at least one order of magnitude. The payload is planned to include an
optical lattice clock, as well as a frequency comb, a microwave link, and an
optical link for comparisons of the ISS clock with ground clocks located in
several countries and continents. Within the EU-FP7-SPACE-2010-1 project no.
263500, during the years 2011-2015 a compact, modular and robust strontium
lattice optical clock demonstrator has been developed. Goal performance is a
fractional frequency instability below 1x10^{-15}, tau^{-1/2} and a fractional
inaccuracy below 5x10^{-17}. Here we describe the current status of the
apparatus' development, including the laser subsystems. Robust preparation of
cold {88}^Sr atoms in a second stage magneto-optical trap (MOT) is achieved.Comment: 27 Pages, 15 figures, Comptes Rendus Physique 201
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