1,701 research outputs found
An integrated source of broadband quadrature squeezed light
An integrated silicon nitride resonator is proposed as an ultra-compact
source of bright single-mode quadrature squeezed light at 850 nm. Optical
properties of the device are investigated and tailored through numerical
simulations, with particular attention paid to loss associated with interfacing
the device. An asymmetric double layer stack waveguide geometry with inverse
vertical tapers is proposed for efficient and robust fibre-chip coupling,
yielding a simulated total loss of -0.75 dB/facet. We assess the feasibility of
the device through a full quantum noise analysis and derive the output
squeezing spectrum for intra-cavity pump self-phase modulation. Subject to
standard material loss and detection efficiencies, we find that the device
holds promises for generating substantial quantum noise squeezing over a
bandwidth exceeding 1 GHz. In the low-propagation loss regime, approximately -7
dB squeezing is predicted for a pump power of only 50 mW.Comment: 23 pages, 12 figure
Verifying continuous variable entanglement of intense light pulses
Three different methods have been discussed to verify continuous variable
entanglement of intense light beams. We demonstrate all three methods using the
same set--up to facilitate the comparison. The non--linearity used to generate
entanglement is the Kerr--effect in optical fibres. Due to the brightness of
the entangled pulses, standard homodyne detection is not an appropriate tool
for the verification. However, we show that by using large asymmetric
interferometers on each beam individually, two non-commuting variables can be
accessed and the presence of entanglement verified via joint measurements on
the two beams. Alternatively, we witness entanglement by combining the two
beams on a beam splitter that yields certain linear combinations of quadrature
amplitudes which suffice to prove the presence of entanglement.Comment: 11 pages, 7 figures, to appear in Phys. Rev.
Experimental Investigation of the Evolution of Gaussian Quantum Discord in an Open System
Gaussian quantum discord is a measure of quantum correlations in Gaussian
systems. Using Gaussian discord we quantify the quantum correlations of a
bipartite entangled state and a separable two-mode mixture of coherent states.
We experimentally analyze the effect of noise addition and dissipation on
Gaussian discord and show that the former noise degrades the discord while the
latter noise for some states leads to an increase of the discord. In
particular, we experimentally demonstrate the near-death of discord by noisy
evolution and its revival through dissipation.Comment: 5 pages, 5 figure
A re-examination of the BEST Trial using composite outcomes, including emergency department visits
Objectives:
The influence of choice of endpoint on trial size, duration, and interpretation of results was examined in patients with heart failure who were enrolled in BEST (Beta-blocker Evaluation of Survival Trial).
Background:
The choice of endpoints in heart failure trials has evolved over the past 3 decades.
Methods:
In the BEST trial, we used Cox regression analysis to examine the effect of bucindolol on the current standard composite of cardiovascular death or heart failure hospitalization (CVD/HFH) compared with the original primary mortality endpoint and the expanded composite that included emergency department (ED) visits. We also undertook an analysis of recurrent events primarily using the Lin, Wei, Ying, and Yang model.
Results:
Overall, 448 (33%) patients on placebo and 411 (30%) patients on bucindolol died (hazard ratio [HR]: 0.90; 95% confidence interval [CI]: 0.78 to 1.02; p = 0.11). A total of 730 (54%) patients experienced CVD/HFH on placebo and 624 (46%) on bucindolol (HR: 0.80; 95% CI: 0.72 to 0.89; p < 0.001). Adding ED visits increased these numbers to 768 (57%) and 668 (49%), respectively (HR: 0.81; 95% CI: 0.73 to 0.90; p < 0.001). A total of 568 (42%) patients on placebo experienced HFH compared with 476 (35%) patients on bucindolol (HR: 0.78; 95% CI: 0.69 to 0.89; p < 0.001), with a total of 1,333 and 1,124 admissions, respectively. With the same statistical assumptions, using the composite endpoint instead of all-cause mortality would have reduced the trial size by 40% and follow-up duration by 69%. The rate ratio for recurrent events (CVD/HFH) was 0.83 (95% CI: 0.73 to 0.94; p = 0.003).
Conclusions:
Choice of endpoint has major implications for trial size and duration, as well as interpretation of results. The value of broader composite endpoints and inclusion of recurrent events needs further investigation. (Beta Blocker Evaluation in Survival Trial [BEST]; NCT00000560
Nitrogen-Vacancy Ensemble Magnetometry Based on Pump Absorption
We demonstrate magnetic field sensing using an ensemble of nitrogen-vacancy
centers by recording the variation in the pump-light absorption due to the
spin-polarization dependence of the total ground state population. Using a 532
nm pump laser, we measure the absorption of native nitrogen-vacancy centers in
a chemical vapor deposited diamond placed in a resonant optical cavity. For a
laser pump power of 0.4 W and a cavity finesse of 45, we obtain a noise floor
of 100 nT/ spanning a bandwidth up to 125 Hz. We
project a photon shot-noise-limited sensitivity of 1
pT/ by optimizing the nitrogen-vacancy concentration and
the detection method.Comment: 7 pages and 5 figure
Practical purification scheme for decohered coherent-state superpositions via partial homodyne detection
We present a simple protocol to purify a coherent-state superposition that
has undergone a linear lossy channel. The scheme constitutes only a single beam
splitter and a homodyne detector, and thus is experimentally feasible. In
practice, a superposition of coherent states is transformed into a classical
mixture of coherent states by linear loss, which is usually the dominant
decoherence mechanism in optical systems. We also address the possibility of
producing a larger amplitude superposition state from decohered states, and
show that in most cases the decoherence of the states are amplified along with
the amplitude.Comment: 8 pages, 10 figure
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