47 research outputs found
Generation of Polarization Squeezing with Periodically Poled KTP at 1064 nm
We report the experimental demonstration of directly produced polarization
squeezing at 1064 nm from a type I optical parametric amplifier (OPA) based on
a periodically poled KTP crystal (PPKTP). The orthogonal polarization modes of
the polarization squeezed state are both defined by the OPA cavity mode, and
the birefringence induced by the PPKTP crystal is compensated for by a second,
but inactive, PPKTP crystal. Stokes parameter squeezing of 3.6 dB and anti
squeezing of 9.4 dB is observed.Comment: 4 pages, 2 figure
Experimental Demonstration of Continuous Variable Cloning with Phase-Conjugate Inputs
We report the experimental demonstration of continuous variable cloning of
phase conjugate coherent states as proposed by Cerf and Iblisdir (Phys. Rev.
Lett. 87, 247903 (2001)). In contrast to the proposal of Cerf and Iblisdir, the
cloning transformation is accomplished using only linear optical components,
homodyne detection and feedforward. Three clones are succesfully produced with
fidelities about 89%.Comment: 5 page
Experimental demonstration of coherent state estimation with minimal disturbance
We investigate the optimal tradeoff between information gained about an
unknown coherent state and the state disturbance caused by the measurement
process. We propose several optical schemes that can enable this task, and we
implement one of them, a scheme which relies on only linear optics and homodyne
detection. Experimentally we reach near optimal performance, limited only by
detection inefficiencies. In addition we show that such a scheme can be used to
enhance the transmission fidelity of a class of noisy channels
Experimental continuous variable cloning of partial quantum information
The fidelity of a quantum transformation is strongly linked with the prior
partial information of the state to be transformed. We illustrate this
interesting point by proposing and demonstrating the superior cloning of
coherent states with prior partial information. More specifically, we propose
two simple transformations that under the Gaussian assumption optimally clone
symmetric Gaussian distributions of coherent states as well as coherent states
with known phases. Furthermore, we implement for the first time near-optimal
state-dependent cloning schemes relying on simple linear optics and
feedforward.Comment: Submitted to PR
Comparison of the marginal adaptation of direct and indirect composite inlay restorations with optical coherence tomography
Objective The purpose of the study was to use the photonic imaging modality of optical coherence tomography (OCT) to compare the marginal adaptation of composite inlays fabricated by direct and indirect techniques. Material and Methods Class II cavities were prepared on 34 extracted human molar teeth. The cavities were randomly divided into two groups according to the inlay fabrication technique. The first group was directly restored on cavities with a composite (Esthet X HD, Dentsply, Germany) after isolating. The second group was indirectly restored with the same composite material. Marginal adaptations were scanned before cementation with an invisible infrared light beam of OCT (Thorlabs), allowing measurement in 200 µm intervals. Restorations were cemented with a self-adhesive cement resin (SmartCem2, Dentsply), and then marginal adaptations were again measured with OCT. Mean values were statistically compared by using independent-samples t-test and paired samples t-test (
Nonunity gain minimal-disturbance measurement
We propose and experimentally demonstrate an optimal non-unity gain Gaussian
scheme for partial measurement of an unknown coherent state that causes minimal
disturbance of the state. The information gain and the state disturbance are
quantified by the noise added to the measurement outcomes and to the output
state, respectively. We derive the optimal trade-off relation between the two
noises and we show that the trade-off is saturated by non-unity gain
teleportation. Optimal partial measurement is demonstrated experimentally using
a linear optics scheme with feed-forward.Comment: 12 page
Universal optical amplification without nonlinearity
We propose and experimentally realize a new scheme for universal
phase-insensitive optical amplification. The presented scheme relies only on
linear optics and homodyne detection, thus circumventing the need for nonlinear
interaction between a pump field and the signal field. The amplifier
demonstrates near optimal quantum noise limited performance for a wide range of
amplification factors.Comment: 5 pages, 4 figure
Environmental Assisted Quantum Information Correction for Continuous Variables
Quantum information protocols are inevitably affected by decoherence which is
associated with the leakage of quantum information into an environment. In this
paper we address the possibility of recovering the quantum information from an
environmental measurement. We investigate continuous variable quantum
information, and we propose a simple environmental measurement that under
certain circumstances fully restores the quantum information of the signal
state although the state is not reconstructed with unit fidelity. We implement
the protocol for which information is encoded into conjugate quadratures of
coherent states of light and the noise added under the decoherence process is
of Gaussian nature. The correction protocol is tested using both a
deterministic as well as a probabilistic strategy. The potential use of the
protocol in a continuous variable quantum key distribution scheme as a means to
combat excess noise is also investigated.Comment: Submitted to PR
Experimental Demonstration of Squeezed State Quantum Averaging
We propose and experimentally demonstrate a universal quantum averaging
process implementing the harmonic mean of quadrature variances. The harmonic
mean protocol can be used to efficiently stabilize a set of fragile squeezed
light sources with statistically fluctuating noise levels. The averaged
variances are prepared probabilistically by means of linear optical
interference and measurement induced conditioning. We verify that the
implemented harmonic mean outperforms the standard arithmetic mean strategy.
The effect of quantum averaging is experimentally tested both for uncorrelated
and partially correlated noise sources with sub-Poissonian shot noise or
super-Poissonian shot noise characteristics.Comment: 4 pages, 5 figure