5,053 research outputs found
Realization of the 1->3 optimal phase-covariant quantum cloning machine
The 1->3 quantum phase covariant cloning, which optimally clones qubits
belonging to the equatorial plane of the Bloch sphere, achieves the fidelity
Fcov(1->3)=0.833, larger than for the 1->3 universal cloning Funiv(1->3)=0.778.
We show how the 1->3 phase covariant cloning can be implemented by a smart
modification of the standard universal quantum machine by a projection of the
output states over the symmetric subspace. A complete experimental realization
of the protocol for polarization encoded qubits based on non-linear and linear
methods will be discussed.Comment: 12 pages, 2 figure
Continuous variable cloning via network of parametric gates
We propose an experimental scheme for the cloning machine of continuous
quantum variables through a network of parametric amplifiers working as
input-output four-port gates.Comment: 4 pages, 2 figures. To appear on Phys. Rev. Let
Implementation of optimal phase-covariant cloning machines
The optimal phase covariant cloning machine (PQCM) broadcasts the information
associated to an input qubit into a multi-qubit systems, exploiting a partial
a-priori knowledge of the input state. This additional a priori information
leads to a higher fidelity than for the universal cloning. The present article
first analyzes different experimental schemes to implement the 1->3 PQCM. The
method is then generalized to any 1->M machine for odd value of M by a
theoretical approach based on the general angular momentum formalism. Finally
different experimental schemes based either on linear or non-linear methods and
valid for single photon polarization encoded qubits are discussed.Comment: 7 pages, 3 figure
Coherent scattering of a Multiphoton Quantum Superposition by a Mirror-BEC
We present the proposition of an experiment in which the multiphoton quantum
superposition consisting of N= 10^5 particles generated by a quantum-injected
optical parametric amplifier (QI-OPA), seeded by a single-photon belonging to
an EPR entangled pair, is made to interact with a Mirror-BEC shaped as a Bragg
interference structure. The overall process will realize a Macroscopic Quantum
Superposition (MQS) involving a microscopic single-photon state of polarization
entangled with the coherent macroscopic transfer of momentum to the BEC
structure, acting in space-like separated distant places.Comment: 4 pages, 4 figure
Complete analysis of measurement-induced entanglement localization on a three-photon system
We discuss both theoretically and experimentally elementary two-photon
polarization entanglement localization after break of entanglement caused by
linear coupling of environmental photon with one of the system photons. The
localization of entanglement is based on simple polarization measurement of the
surrounding photon after the coupling. We demonstrate that non-zero
entanglement can be localized back irrespectively to the distinguishability of
coupled photons. Further, it can be increased by local single-copy polarization
filters up to an amount violating Bell inequalities. The present technique
allows to restore entanglement in that cases, when the entanglement
distillation does not produce any entanglement out of the coupling.Comment: 14 pages, 14 figures, submitted to Phys. Rev.
Input-Output Relations in Optical Cavities: a Simple Point of View
In this work we present a very simple approach to input-output relations in
optical cavities, limiting ourselves to one- and two-photon states of the
field.
After field quantization, we derive the non-unitary transformation between
{\em Inside} and {\em Outside} annihilation and creation operators. Then we
express the most general two-photon state generated by {\em Inside} creation
operators, through base states generated by {\em Outside} creation operators.
After renormalization of coefficients of inside two-photon state, we calculate
the outside photon-number probability distribution in a general case. Finally
we treat with some detail the single mode and symmetrical cavity case.Comment: 34 pages, 5 figures jpg, LaTe
Realization of the Optimal Universal Quantum Entangler
We present the first experimental demonstration of the ''optimal'' and
''universal'' quantum entangling process involving qubits encoded in the
polarization of single photons. The structure of the ''quantum entangling
machine'' consists of the quantum injected optical parametric amplifier by
which the contextual realization of the 1->2 universal quantum cloning and of
the universal NOT (U-NOT) gate has also been achieved.Comment: 10 pages, 3 figures, to appear in Physical Review
Preliminary slip rate estimates for the Düzce segment of the North Anatolian Fault Zone from offset geomorphic markers
New estimates on the Quaternary slip rate of the active transform margin of North Anatolia are provided. We investigated the area struck by the 12th November 1999, Mw 7.1 earthquake, that ruptured the Düzce fault segment of the North Anatolian Fault. In order to analyze the spectacular tectonically driven cumulative landforms and the drainage pattern settings, we carried out a 1:25,000-scale geological and geomorphological mapping along the fault trace. We reconstruct and describe, as offset geomorphic markers, right-hand stream deflections and fluvial terraces inset into alluvial fan deposits. Radiocarbon dating indicates that ~100 m stream deflections were built up by the last ~7000 yrs of fault activity. Conversely, two documented and correlated Late Pleistocene fluvial terraces are horizontally offset by ~300 and ~900 m, respectively. These were dated by means of Optically Stimulated Luminescence (OSL) to ~21 ka BP and 60 ka BP. Assuming a constant rate of deformation for the Düzce Fault, ages and related offsets translate to consistent slip-rates that yield an average slip-rate of 15.0 ± 3.2 mm/yr for the last 60 ka. Thus, the Düzce Fault importantly contributes to the North Anatolian margin deformation, suggesting a present-day partitioning of displacement rates with the Mudurnu fault to the south and confirming its important role in the seismic hazard of the area
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