722 research outputs found
Polarization Squeezing of Continuous Variable Stokes Parameters
We report the first direct experimental characterization of continuous
variable quantum Stokes parameters. We generate a continuous wave light beam
with more than 3 dB of simultaneous squeezing in three of the four Stokes
parameters. The polarization squeezed beam is produced by mixing two quadrature
squeezed beams on a polarizing beam splitter. Depending on the squeezed
quadrature of these two beams the quantum uncertainty volume on the
Poincar\'{e} sphere became a `cigar' or `pancake'-like ellipsoid.Comment: 4 pages, 5 figure
Polarization squeezing with cold atoms
We study the interaction of a nearly resonant linearly polarized laser beam
with a cloud of cold cesium atoms in a high finesse optical cavity. We show
theoretically and experimentally that the cross-Kerr effect due to the
saturation of the optical transition produces quadrature squeezing on both the
mean field and the orthogonally polarized vacuum mode. An interpretation of
this vacuum squeezing as polarization squeezing is given and a method for
measuring quantum Stokes parameters for weak beams via a local oscillator is
developed
Cavity-enhanced sum-frequency generation of blue light with near-unity conversion efficiency
We report on double-resonant highly efficient sum-frequency generation in the
blue range. The system consists of a 10-mm-long periodically poled KTP crystal
placed in a double-resonant bow-tie cavity and pumped by a fiber laser at
1064.5 nm and a Ti:sapphire laser at 849.2 nm. An optical power of 375 mW at
472.4 nm in a TEM mode was generated with pump powers of 250 mW at 849.2
nm and 200 mW at 1064.5 nm coupled into the double-resonant ring resonator with
88 mode-matching. The resulting internal conversion efficiency of 95() of the photons mode-matched to the cavity constitutes, to the best of
our knowledge, the highest overall achieved quantum conversion efficiency using
continuous-wave pumping. Very high conversion efficiency is rendered possible
due to very low intracavity loss on the level of 0.3 and high nonlinear
conversion coefficient up to 0.045(0.015) W. Power stability
measurements performed over one hour show a stability of 0.8. The generated
blue light can be tuned within 5 nm around the center wavelength of 472.4 nm,
limited by the phase-matching of our nonlinear crystal. This can however be
expanded to cover the entire blue spectrum (420 nm to 510 nm) by proper choice
of nonlinear crystals and pump lasers. Our experimental results agree very well
with analytical and numerical simulations taking into account cavity impedance
matching and depletion of the pump fields.Comment: 9 pages, 5 figure
Entanglement and spin squeezing in the two-atom Dicke model
We analyze the relation between the entanglement and spin-squeezing parameter
in the two-atom Dicke model and identify the source of the discrepancy recently
reported by Banerjee and Zhou et al that one can observe entanglement without
spin squeezing. Our calculations demonstrate that there are two criteria for
entanglement, one associated with the two-photon coherences that create
two-photon entangled states, and the other associated with populations of the
collective states. We find that the spin-squeezing parameter correctly predicts
entanglement in the two-atom Dicke system only if it is associated with
two-photon entangled states, but fails to predict entanglement when it is
associated with the entangled symmetric state. This explicitly identifies the
source of the discrepancy and explains why the system can be entangled without
spin-squeezing. We illustrate these findings in three examples of the
interaction of the system with thermal, classical squeezed vacuum and quantum
squeezed vacuum fields.Comment: 7 pages, 1 figur
Experimental demonstration of quantum memory for light
The information carrier of today's communications, a weak pulse of light, is
an intrinsically quantum object. As a consequence, complete information about
the pulse cannot, even in principle, be perfectly recorded in a classical
memory. In the field of quantum information this has led to a long standing
challenge: how to achieve a high-fidelity transfer of an independently prepared
quantum state of light onto the atomic quantum state? Here we propose and
experimentally demonstrate a protocol for such quantum memory based on atomic
ensembles. We demonstrate for the first time a recording of an externally
provided quantum state of light onto the atomic quantum memory with a fidelity
up to 70%, significantly higher than that for the classical recording. Quantum
storage of light is achieved in three steps: an interaction of light with
atoms, the subsequent measurement on the transmitted light, and the feedback
onto the atoms conditioned on the measurement result. Density of recorded
states 33% higher than that for the best classical recording of light on atoms
is achieved. A quantum memory lifetime of up to 4 msec is demonstrated.Comment: 22 pages (double line spacing) incl. supplementary information, 4
figures, accepted for publication in Natur
Three-dimensional theory for interaction between atomic ensembles and free-space light
Atomic ensembles have shown to be a promising candidate for implementations
of quantum information processing by many recently-discovered schemes. All
these schemes are based on the interaction between optical beams and atomic
ensembles. For description of these interactions, one assumed either a
cavity-QED model or a one-dimensional light propagation model, which is still
inadequate for a full prediction and understanding of most of the current
experimental efforts which are actually taken in the three-dimensional free
space. Here, we propose a perturbative theory to describe the three-dimensional
effects in interaction between atomic ensembles and free-space light with a
level configuration important for several applications. The calculations reveal
some significant effects which are not known before from the other approaches,
such as the inherent mode-mismatching noise and the optimal mode-matching
conditions. The three-dimensional theory confirms the collective enhancement of
the signal-to-noise ratio which is believed to be one of the main advantage of
the ensemble-based quantum information processing schemes, however, it also
shows that this enhancement need to be understood in a more subtle way with an
appropriate mode matching method.Comment: 16 pages, 9 figure
Inverse spectral problems for Sturm-Liouville operators with singular potentials
The inverse spectral problem is solved for the class of Sturm-Liouville
operators with singular real-valued potentials from the space .
The potential is recovered via the eigenvalues and the corresponding norming
constants. The reconstruction algorithm is presented and its stability proved.
Also, the set of all possible spectral data is explicitly described and the
isospectral sets are characterized.Comment: Submitted to Inverse Problem
Coupling of effective one-dimensional two-level atoms to squeezed light
A cavity QED system is analyzed which duplicates the dynamics of a two-level
atom in free space interacting exclusively with broadband squeezed light. We
consider atoms in a three or four-level Lambda-configuration coupled to a
high-finesse optical cavity which is driven by a squeezed light field. Raman
transitions are induced between a pair of stable atomic ground states via the
squeezed cavity mode and coherent driving fields. An analysis of the reduced
master equation for the atomic ground states shows that a three-level atomic
system has insufficient parameter flexibility to act as an effective two-level
atom interacting exclusively with a squeezed reservoir. However, the inclusion
of a fourth atomic level, coupled dispersively to one of the two ground states
by an auxiliary laser field, introduces an extra degree of freedom and enables
the desired interaction to be realised. As a means of detecting the reduced
quadrature decay rate of the effective two-level system, we examine the
transmission spectrum of a weak coherent probe field incident upon the cavity
Successful aging and changes in sexual interest and enjoyment among older European men and women
Introduction
Despite the popularity and analytical relevance of the concept of successful aging, little efforts have been made to address its relationship to sexuality in older individuals.
Aim
To explore the relationship between successful aging and the (retrospectively assessed) change in sexual interest and enjoyment in the past 10 years, using a new multidimensional model of successful aging.
Methods
The data for this study was collected in 2016 using national probability-based surveys in four European countries (Norway, Denmark, Belgium and Portugal). In total, information from 2,461 sexually active and inactive participants aged 60–75 years was used for analyses. Multigroup structural equation analysis was employed to address the associations between key constructs.
Main Outcome Measure
The dependent variable was a composite (two-item) indicator of change in sexual interest and enjoyment in the past 10 years; a multifaceted model of successful aging predicted the change by country and gender.
Results
Tested cross-culturally, the proposed model of successful aging demonstrated a good fit to the data. Furthermore, its metric characteristics enabled direct comparisons across gender and national cultures. Controlling for sociodemographic characteristics, higher successful aging scores were consistently related to lower reduction in sexual interest/enjoyment among men and women across the 4 countries.
Clinical Implications
Given an increased life-expectancy and focus on healthy aging in many countries, the findings about the associations between sexual expression, quality of life and aging well are valuable to professionals working in the area of healthy sexual aging.
Strength & Limitations
This is the first study to systematically address the relationship between successful aging and sexuality. Furthermore, it provides a multidimensional measure of successful aging for a wide range of sexologic studies. Among limitations, possible self-selection bias (toward more sexually permissive and sexually active participants) and the fact that the findings are restricted to older heterosexual individuals, should be considered.
Conclusion
Without stigmatizing the absence of sexual expression in aging individuals, the findings from this cross-cultural study point out that sustained sexual interest and sexual enjoyment are linked to successful aging in both genders
Entangling Two Bose-Einstein Condensates by Stimulated Bragg Scattering
We propose an experiment for entangling two spatially separated Bose-Einstein
condensates by Bragg scattering of light. When Bragg scattering in two
condensates is stimulated by a common probe, the resulting quasiparticles in
the two condensates get entangled due to quantum communication between the
condensates via probe beam. The entanglement is shown to be significant and
occurs in both number and quadrature phase variables. We present two methods of
detecting the generated entanglement.Comment: 4 pages, Revte
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