412 research outputs found
Trihamiltonian extensions of separable systems in the plane
A method to construct trihamiltonian extensions of a separable system is
presented. The procedure is tested for systems, with a natural Hamiltonian,
separable in classical sense in one of the four orthogonal separable coordinate
systems of the Euclidean plane, and some explicit examples are constructed.
Finally a conjecture on possible generalizations to other classes of systems is
discussed: in particular, the method can be easily adapted to the eleven
orthogonal separable coordinate sets of the Euclidean three-space.Comment: 20 page
Quantum detection of electronic flying qubits
We consider a model of a detector of ballistic electrons at the edge of a
two-dimensional electron gas in the integer quantum Hall regime. The electron
is detected by capacitive coupling to a gate which is also coupled to a passive
RC circuit. Using a quantum description of this circuit, we determine the
signal over noise ratio of the detector in term of the detector
characteristics. The back-action of the detector on the incident wavepacket is
then computed using a Feynman-Vernon influence functional approach. Using
information theory, we define the appropriate notion of quantum limit for such
an "on the fly" detector. We show that our particular detector can approach the
quantum limit up to logarithms in the ratio of the measurement time over the RC
relaxation time. We argue that such a weak logarithmic effect is of no
practical significance. Finally we show that a two-electron interference
experiment can be used to probe the detector induced decoherence.Comment: 15 pages, 7 figures, published versio
Toward third order ghost imaging with thermal light
Recently it has been suggested that an enhancement in the visibility of ghost
images obtained with thermal light can be achieved exploiting higher order
correlations [3]. This paper reports on the status of an higher order ghost
imaging experiment carried on at INRIM labs exploiting a pseudo-thermal source
and a CCD camera.Comment: To be published in Proceedings of Recent advances in Foundations of
Quantum Mechanics and Quantum Informatio
Intensity correlations, entanglement properties and ghost imaging in multimode thermal-seeded parametric downconversion: Theory
We address parametric-downconversion seeded by multimode pseudo-thermal
fields. We show that this process may be used to generate multimode pairwise
correlated states with entanglement properties that can be tuned by controlling
the seed intensities. Multimode pseudo-thermal fields seeded
parametric-downconversion represents a novel source of correlated states, which
allows one to explore the classical-quantum transition in pairwise correlations
and to realize ghost imaging and ghost diffraction in regimes not yet explored
by experiments.Comment: 9 pages, 3 figure
Revealing interference by continuous variable discordant states
In general, a pair of uncorrelated Gaussian states mixed in a beam splitter
produces a correlated state at the output. However, when the inputs are
identical Gaussian states the output state is equal to the input, and no
correlations appear, as the interference had not taken place. On the other
hand, since physical phenomena do have observable effects, and the beam
splitter is there, a question arises on how to reveal the interference between
the two beams. We prove theoretically and demonstrate experimentally that this
is possible if at least one of the two beams is prepared in a discordant, i.e.
Gaussian correlated, state with a third beam. We also apply the same technique
to reveal the erasure of polarization information. Our experiments involves
thermal states and the results show that Gaussian discordant states, even when
they show a positive Glauber P-function, may be useful to achieve specific
tasks.Comment: published versio
Tri-hamiltonian vector fields, spectral curves and separation coordinates
We show that for a class of dynamical systems, Hamiltonian with respect to
three distinct Poisson brackets (P_0, P_1, P_2), separation coordinates are
provided by the common roots of a set of bivariate polynomials. These
polynomials, which generalise those considered by E. Sklyanin in his
algebro-geometric approach, are obtained from the knowledge of: (i) a common
Casimir function for the two Poisson pencils (P_1 - \lambda P_0) and (P_2 - \mu
P_0); (ii) a suitable set of vector fields, preserving P_0 but transversal to
its symplectic leaves. The frameworks is applied to Lax equations with spectral
parameter, for which not only it unifies the separation techniques of Sklyanin
and of Magri, but also provides a more efficient ``inverse'' procedure not
involving the extraction of roots.Comment: 49 pages Section on reduction revisite
Real time decoherence of Landau and Levitov quasi-particles in quantum Hall edge channels
Quantum Hall edge channels at integer filling factor provide a unique
test-bench to understand decoherence and relaxation of single electronic
excitations in a ballistic quantum conductor. In this Letter, we obtain a full
visualization of the decoherence scenario of energy (Landau) and time (Levitov)
resolved single electron excitations at filling factor . We show that
the Landau excitation exhibits a fast relaxation followed by spin-charge
separation whereas the Levitov excitation only experiences spin-charge
separation. We finally suggest to use Hong-Ou-Mandel type experiments to probe
specific signatures of these different scenarios.Comment: 14 pages, 8 figure
Realization of a twin beam source based on four-wave mixing in Cesium
Four-wave mixing (4WM) is a known source of intense non-classical twin beams.
It can be generated when an intense laser beam (the pump) and a weak laser beam
(the seed) overlap in a medium (here cesium vapor), with
frequencies close to resonance with atomic transitions. The twin beams
generated by 4WM have frequencies naturally close to atomic transitions, and
can be intense (gain ) even in the CW pump regime, which is not the case
for PDC phenomenon in non-linear crystals. So, 4WM is well suited
for atom-light interaction and atom-based quantum protocols. Here we present
the first realization of a source of 4-wave mixing exploiting line of
Cesium atoms.Comment: 10 pages, 10 figure
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