246 research outputs found
Quantum Key Distribution using Multilevel Encoding: Security Analysis
We present security proofs for a protocol for Quantum Key Distribution (QKD)
based on encoding in finite high-dimensional Hilbert spaces. This protocol is
an extension of Bennett's and Brassard's basic protocol from two bases, two
state encoding to a multi bases, multi state encoding. We analyze the mutual
information between the legitimate parties and the eavesdropper, and the error
rate, as function of the dimension of the Hilbert space, while considering
optimal incoherent and coherent eavesdropping attacks. We obtain the upper
limit for the legitimate party error rate to ensure unconditional security when
the eavesdropper uses incoherent and coherent eavesdropping strategies. We have
also consider realistic noise caused by detector's noise.Comment: 8 pages, 3 figures, REVTe
Three-body decay of a rubidium Bose-Einstein condensate
We have measured the three-body decay of a Bose-Einstein condensate of
rubidium (Rb) atoms prepared in the doubly polarized ground state
. Our data are taken for a peak atomic density in the condensate
varying between cm at initial time and cm, 16 seconds later. Taking into account the influence of the
uncondensed atoms onto the decay of the condensate, we deduce a rate constant
for condensed atoms cms. For
these densities we did not find a significant contribution of two-body
processes such as spin dipole relaxation.Comment: 14 pages, 4 figure
Semiquantum key distribution using entangled states
Recently, Boyer et al. presented a novel semiquantum key distribution
protocol [M. Boyer, D. Kenigsberg, and T. Mor, Phys. Rev. Lett. 99, 140501
(2007)], by using four quantum states, each of which is randomly prepared by Z
basis or X basis. Here we present a semiquantum key distribution protocol by
using entangled states in which quantum Alice shares a secret key with
classical Bob. We also show the protocol is secure against eavesdropping.Comment: 6 page
Quantum key distribution with realistic states: photon-number statistics in the photon-number splitting attack
Quantum key distribution can be performed with practical signal sources such
as weak coherent pulses. One example of such a scheme is the Bennett-Brassard
protocol that can be implemented via polarization of the signals, or equivalent
signals. It turns out that the most powerful tool at the disposition of an
eavesdropper is the photon-number splitting attack. We show that this attack
can be extended in the relevant parameter regime such as to preserve the
Poissonian photon number distribution of the combination of the signal source
and the lossy channel.Comment: 4 page
Security of EPR-based Quantum Cryptography against Incoherent Symmetric Attacks
We investigate a new strategy for incoherent eavesdropping in Ekert's
entanglement based quantum key distribution protocol. We show that under
certain assumptions of symmetry the effectiveness of this strategy reduces to
that of the original single qubit protocol of Bennett and Brassard
Gastric Varices with Remarkable Collateral Veins in Valpronic Acid-Induced Chronic Pancreatitis
Valproic acid (VPA) is a commonly prescribed and approved treatment for epilepsy, including Angelman syndrome, throughout the world. However, the long-term administration of drugs like VPA is associated with the possible development of gastric varices and splenic obstruction as a result of chronic pancreatitis. Such cases can be difficult to treat using endoscopy or interventional radiology because of hemodynamic abnormalities; therefore, surgical treatment is often necessary
High-capacity quantum secure direct communication based on quantum hyperdense coding with hyperentanglement
We present a quantum hyperdense coding protocol with hyperentanglement in
polarization and spatial-mode degrees of freedom of photons first and then give
the details for a quantum secure direct communication (QSDC) protocol based on
this quantum hyperdense coding protocol. This QSDC protocol has the advantage
of having a higher capacity than the quantum communication protocols with a
qubit system. Compared with the QSDC protocol based on superdense coding with
-dimensional systems, this QSDC protocol is more feasible as the preparation
of a high-dimension quantum system is more difficult than that of a two-level
quantum system at present.Comment: 5 pages, 2 figur
Gastric Inflammatory Fibroid Polyp Treated by Endoscopic Submucosal Dissection
The endoscopic examination of a 64-year-old male patient revealed a gastric submucosal tumor in the anterior wall of the gastric antrum. The lesion increased in diameter to 25 mm and was resected completely with endoscopic submucosal dissection (ESD). Histological examination of the submucosal tumor gave a diagnosis of an inflammatory fibroid polyp (IFP). It is suggested that ESD may be an effective and safe therapy for gastric submucosal tumors
General theory for decoy-state quantum key distribution with arbitrary number of intensities
We develop a general theory for quantum key distribution (QKD) in both the
forward error correction and the reverse error correction cases when the QKD
system is equipped with phase-randomized coherent light with arbitrary number
of decoy intensities. For this purpose, generalizing Wang's expansion, we
derive a convex expansion of the phase-randomized coherent state. We also
numerically check that the asymptotic key generation rates are almost saturated
when the number of decoy intensities is three.Comment: This manuscript has been revised extensivel
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