23 research outputs found
Extremal Quantum Correlations: Experimental Study with Two-qubit States
We explore experimentally the space of two-qubit quantum correlated mixed
states, including frontier ones as defined by the use of quantum discord and
von Neumann entropy. Our experimental setup is flexible enough to allow for the
high-quality generation of a vast variety of states. We address quantitatively
the relation between quantum discord and a recently suggested alternative
measure of quantum correlations.Comment: 5 pages, 2 figure
Experimental Realization of the Deutsch-Jozsa Algorithm with a Six-Qubit Cluster State
We describe the first experimental realization of the Deutsch-Jozsa quantum
algorithm to evaluate the properties of a 2-bit boolean function in the
framework of one-way quantum computation. For this purpose a novel two-photon
six-qubit cluster state was engineered. Its peculiar topological structure is
the basis of the original measurement pattern allowing the algorithm
realization. The good agreement of the experimental results with the
theoretical predictions, obtained at 1kHz success rate, demonstrate the
correct implementation of the algorithm.Comment: 5 pages, 2 figures, RevTe
Multi-path entanglement of two photons
We present a novel optical device based on an integrated system of
micro-lenses and single mode optical fibers. It allows to collect and direct
into many modes two photons generated by spontaneous parametric down
conversion. By this device multiqubit entangled states and/or multilevel
qu-it states of two photons, encoded in the longitudinal momentum degree of
freedom, are created. The multi-path photon entanglement realized by this
device is expected to find important applications in modern quantum information
technology.Comment: 4 pages, 3 figures, revtex, revised versio
Experimental achievement of the entanglement assisted capacity for the depolarizing channel
We experimentally demonstrate the achievement of the entanglement assisted
capacity for classical information transmission over a depolarizing channel.
The implementation is based on the generation and local manipulation of 2-qubit
Bell states, which are finally measured at the receiver by a complete Bell
state analysis. The depolarizing channel is realized by introducing quantum
noise in a controlled way on one of the two qubits. This work demonstrates the
achievement of the maximum allowed amount of information that can be shared in
the presence of noise and the highest reported value in the noiseless case.Comment: 4 pages, 3 figure
Simplified Quantum Process Characterization by Specialised Neural Networks
Characterization of quantum objects based on previous knowledge is a valuable
approach, especially as it leads to routine procedures for real-life
components. To this end, Machine Learning algorithms have demonstrated to
successfully operate in presence of noise. However, there might be instances in
which unknown parasitic effects occur in tandem with the sought one we aim at
characterizing. Here we show that the accurate design of a two-stage neural
network can account for these class of disturbances as well, applying our
technique to the characterization of several quantum channels. We demonstrate
that a stable and reliable characterization is achievable by training the
network only with simulated data. The obtained results show the viability of
this approach as an effective tool based on a completely new paradigm for the
employment of NNs in the quantum domain
Fully nonlocal quantum correlations
Quantum mechanics is a nonlocal theory, but not as nonlocal as the
no-signalling principle allows. However, there exist quantum correlations that
exhibit maximal nonlocality: they are as nonlocal as any non-signalling
correlations and thus have a local content, quantified by the fraction of
events admitting a local description, equal to zero. Exploiting the link
between the Kochen-Specker and Bell's theorems, we derive, from every
Kochen-Specker proof, Bell inequalities maximally violated by quantum
correlations. We then show that these Bell inequalities lead to experimental
bounds on the local content of quantum correlations which are significantly
better than those based on other constructions. We perform the experimental
demonstration of a Bell test originating from the Peres-Mermin Kochen-Specker
proof, providing an upper bound on the local content .Comment: 9 pages, 5 figures and three tables. To appear in PR
Fast remote spectral discrimination through ghost spectrometry
Assessing the presence of chemical, biological, radiological and nuclear
threats is a crucial task which is usually dealt with by analyzing the presence
of spectral features in a measured absorption profile. The use of quantum light
allows to perform these measurements remotely without compromising the
measurement accuracy through ghost spectrometry. However, in order to have
sufficient signal-to-noise ratio, it is typically required to wait long
acquisition times, hence subtracting to the benefits provided by remote
sensing. In many instances, though, reconstructing the full spectral lineshape
of an object is not needed and the interest lies in discriminating whether a
spectrally absorbing object may be present or not. Here we show that this task
can be performed fast and accurately through ghost spectrometry by comparing
the low resources measurement with a reference. We discuss the experimental
results obtained with different samples and complement them with simulations to
explore the most common scenarios
intravenous versus oral vinorelbine plus capecitabine as second line treatment in advanced breast cancer patients a retrospective comparison of two consecutive phase ii studies
Abstract Vinorelbine (i.v.) plus capecitabine (oral) combination therapy is active in anthracycline/taxane pretreated patients with metastatic breast cancer. Availability of oral vinorelbine provides this combination in an all-oral formulation. Two consecutive phase II trials differing only in vinorelbine administration routes evaluated their respective activities and tolerabilities in this population. In the i.v. group ( n = 38) disease control was 61% (37% PR, 24% SD), median TTP 6.8 months and median survival 11.3 months. In the oral group ( n = 38) disease control was 77% (5.4% CR, 34% PR, 38% SD), median TTP 7 months and median survival 10 months. G3–G4 neutropenia was more common in the oral group (
Phase control of a longitudinal momentum entangled photon state by a deformable membrane mirror
We propose a paradigmatic demonstration of the potentialities of a deformable
mirror for closed-loop control of a two-photon momentum-entangled state,
subject to phase fluctuations. A custom-made membrane mirror is used to set a
relative phase shift between the arms of an interferometric apparatus. The
control algorithm estimates the phase of the quantum state, by measurements of
the coincidence events at the output ports of the interferometer, and uses the
measurements results to provide a feedback signal to the deformable mirror.
Stabilization of the coincidence rate to within 1.5 standard deviation of the
Poissonian noise is demonstrated over 2000 seconds.Comment: RevTex, 6 page