961 research outputs found
Spin squeezing in optical lattice clocks via lattice-based QND measurements
Quantum projection noise will soon limit the best achievable precision of
optical atomic clocks based on lattice-confined neutral atoms. Squeezing the
collective atomic pseudo-spin via measurement of the clock state populations
during Ramsey interrogation suppresses the projection noise. We show here that
the lattice laser field can be used to perform ideal quantum non-demolition
measurements without clock shifts or decoherence and explore the feasibility of
such an approach in theory with the lattice field confined in a ring-resonator.
Detection of the motional sideband due to the atomic vibration in the lattice
wells can yield signal sizes a hundredfold above the projection noise limit.Comment: Substantially expanded versio
Reconstruction of the phase of matter-wave fields using a momentum resolved cross-correlation technique
We investigate the potential of the so-called XFROG cross-correlation
technique originally developed for ultrashort laser pulses for the recovery of
the amplitude and phase of the condensate wave function of a Bose-Einstein
condensate. Key features of the XFROG method are its high resolution,
versatility and stability against noise and some sources of systematic errors.
After showing how an analogue of XFROG can be realized for Bose-Einstein
condensates, we illustrate its effectiveness in determining the amplitude and
phase of the wave function of a vortex state. The impact of a reduction of the
number of measurements and of typical sources of noise on the field
reconstruction are also analyzed.Comment: 7 pages; 9 figures; article with higher resolution figures available
from author
Extreme non-linear response of ultra-narrow optical transitions in cavity QED for laser stabilization
We explore the potential of direct spectroscopy of ultra-narrow optical
transitions of atoms localized in an optical cavity. In contrast to
stabilization against a reference cavity, which is the approach currently used
for the most highly stabilized lasers, stabilization against an atomic
transition does not suffer from Brownian thermal noise. Spectroscopy of
ultra-narrow optical transitions in a cavity operates in a very highly
saturated regime in which non-linear effects such as bistability play an
important role. From the universal behavior of the Jaynes-Cummings model with
dissipation, we derive the fundamental limits for laser stabilization using
direct spectroscopy of ultra-narrow atomic lines. We find that with current
lattice clock experiments, laser linewidths of about 1 mHz can be achieved in
principle, and the ultimate limitations of this technique are at the 1 Hz
level.Comment: 5 pages, 4 figure
Non-destructive cavity QED probe of Bloch oscillations in a gas of ultracold atoms
We describe a scheme for probing a gas of ultracold atoms trapped in an
optical lattice and moving in the presence of an external potential. The probe
is non-destructive and uses the existing lattice fields as the measurement
device. Two counter-propagating cavity fields simultaneously set up a
conservative lattice potential and a weak quantum probe of the atomic motion.
Balanced heterodyne detection of the probe field at the cavity output along
with integration in time and across the atomic cloud yield information about
the atomic dynamics in a single run. The scheme is applied to a measurement of
the Bloch oscillation frequency for atoms moving in the presence of the local
gravitational potential. Signal-to-noise ratios are estimated to be as high as
.Comment: 8 pages, 6 figures, submitted to Phys. Rev.
Prospects for a mHz-linewidth laser
We propose a new light source based on having alkaline-earth atoms in an
optical lattice collectively emit photons on an ultra-narrow clock transition
into the mode of a high Q-resonator. The resultant optical radiation has an
extremely narrow linewidth in the mHz range, even smaller than that of the
clock transition itself due to collective effects. A power level of order
is possible, sufficient for phase-locking a slave optical local
oscillator. Realizing this light source has the potential to improve the
stability of the best clocks by two orders of magnitude.Comment: minor revisions + shortening; factor 2 algebra mistake correcte
Intensity fluctuations in steady state superradiance
Alkaline-earth like atoms with ultra-narrow optical transitions enable
superradiance in steady state. The emitted light promises to have an
unprecedented stability with a linewidth as narrow as a few millihertz. In
order to evaluate the potential usefulness of this light source as an
ultrastable oscillator in clock and precision metrology applications it is
crucial to understand the noise properties of this device. In this paper we
present a detailed analysis of the intensity fluctuations by means of
Monte-Carlo simulations and semi-classical approximations. We find that the
light exhibits bunching below threshold, is to a good approximation coherent in
the superradiant regime, and is chaotic above the second threshold.Comment: 8 pages, 5 figure
A survey of evidence-based practice, training, supervision and clinician confidence relating to post-traumatic stress disorder (PTSD) therapies in UK child and adolescent mental health professionals
Background: Post-Traumatic Stress Disorder (PTSD) in children and adolescents has received increasing recognition in recent decades. Despite development of treatments and improved dissemination efforts, research has identified a number of barriers to implementing these approaches.
Objective: This study sought to understand what interventions mental health professionals working with children and adolescents utilised to treat PTSD, their training and supervision, their confidence in assessing and treating PTSD, and how these factors relate to clinicians characteristics (e.g. age, gender, professional background).
Method: The study comprised an internet-delivered survey of clinicians working in child and adolescent mental health services in the UK (N = 716).
Results: Many clinicians (>40%) had not received training in working with PTSD, with considerable variation between professional background. Lack of training and supervision was associated with reduced clinician confidence in treating children with PTSD (possible range 0–10; training M = 7.54, SD = 1.65, no training M = 5.49, SD = 2.29; supervision M = 7.53, SD = 1.63, no supervision M = 5.98, SD = 2.35). Evidence-based therapies for PTSD such as Trauma-Focused Cognitive-Behavioural Therapy and Eye Movement Desensitisation and Reprocessing were only endorsed modestly by clinicians (58.4% and 37.5%, respectively). Regression analyses identified that lack of training and supervision were significant barriers to the use of evidence-based interventions. Other predictors of clinician confidence and use of evidence-based interventions included profession and years of experience. Participants almost universally wanted more training in working with PTSD.
Conclusions: Evidence-based treatments are not currently universally delivered by mental health professionals in the UK, with certain professions particularly lacking training and confidence with this condition. Training around trauma and PTSD may be an ongoing need to boost and maintain confidence in working with PTSD in youth
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