1,367 research outputs found
Experimental Realization of Polarization Qutrits from Non-Maximally Entangled States
Based on a recent proposal [Phys. Rev. A 71, 062337 (2005)], we have
experimentally realized two photon polarization qutrits by using non-maximally
entangled states and linear optical transformations. By this technique high
fidelity mutually unbiased qutrits are generated at a high brilliance level.Comment: RevTex, 8 pages, 6 figure
Hyperentanglement witness
A new criterium to detect the entanglement present in a {\it hyperentangled
state}, based on the evaluation of an entanglement witness, is presented. We
show how some witnesses recently introduced for graph states, measured by only
two local settings, can be used in this case. We also define a new witness
that improves the resistance to noise by increasing the number of local
measurements.Comment: 6 pages, 2 figures, RevTex. v2: new title, minor changes in the
explanation of the witness for hyperentangled states, more comments in the
conclusions sectio
Realization and characterization of a 2-photon 4-qubit linear cluster state
We report on the experimental realization of a 4-qubit linear cluster state
via two photons entangled both in polarization and linear momentum. This state
was investigated by performing tomographic measurements and by evaluating an
entanglement witness. By use of this state we carried out a novel nonlocality
proof, the so-called ``stronger two observer all versus nothing'' test of
quantum nonlocality.Comment: 4 pages, 4 figure
Hyperentanglement of two photons in three degrees of freedom
A 6-qubit hyperentangled state has been realized by entangling two photons in
three degrees of freedom. These correspond to the polarization, the
longitudinal momentum and the indistinguishable emission produced by a
2-crystal system operating with Type I phase matching in the spontaneous
parametric down conversion regime. The state has been characterized by a
chained interferometric apparatus and its complete entangled nature has been
tested by a novel witness criterium specifically introduced for hyperentangled
states. The experiment represents the first realization of a genuine
hyperentangled state with the maximum entanglement between the two particles
allowed in the given Hilbert space.Comment: 4 pages, 2 figures, Revtex
Generation of time-bin entangled photons without temporal post-selection
We report on the implementation of a new interferometric scheme that allows
the generation of photon pairs entangled in the time-energy degree of freedom.
This scheme does not require any kind of temporal post-selection on the
generated pairs and can be used even with lasers with short coherence time.Comment: RevTex, 6 pages, 8 figure
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
Polarization entanglement with GRaded-INdex lenses
By using an optical device based on the integration of a GRaded-INdex (GRIN)
rod lens and a single-mode optical fiber we efficiently collected photon pairs
generated by spontaneous parametric down-conversion. We show that this system
preserves the polarization entanglement of the 2-photon states. Hence this
device, characterized by a remarkable easiness of alignment and allowing for
high coupling efficiency of single-mode radiation, can be used with photons
entangled in various degrees of freedom, such as polarization and spatial
momentum, and to interconnect different sides of complex optical circuits.Comment: 4 pages, 4 figures, version
Enhancing the Violation of the Einstein-Podolsky-Rosen Local Realism by Quantum Hyper-entanglement
Mermin's observation [Phys. Rev. Lett. {\bf 65}, 1838 (1990)] that the
magnitude of the violation of local realism, defined as the ratio between the
quantum prediction and the classical bound, can grow exponentially with the
size of the system is demonstrated using two-photon hyper-entangled states
entangled in polarization and path degrees of freedom, and local measurements
of polarization and path simultaneously.Comment: Minor errors corrected. To appear on Physical Review Letter
Experimental Entanglement and Nonlocality of a Two-Photon Six-Qubit Cluster State
We create a six-qubit linear cluster state by transforming a two-photon
hyperentangled state in which three qubits are encoded in each particle, one in
the polarization and two in the linear momentum degrees of freedom. For this
state, we demonstrate genuine six-qubit entanglement, persistency of
entanglement against the loss of qubits, and higher violation than in previous
experiments on Bell inequalities of the Mermin type.Comment: 4 pages, revtex, published versio
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