1,294 research outputs found
Abstract of the Journal of a Route Travelled by Captain S. F. Hannay, of the 40th Regiment, Native Infantry, in 1835-36, from the Capital of Ava to the Amber Mines of the Hukong Valley on the South-east Frontier of Assam by R. Boileau Pemberton, edited by Michael W. Charney
This abstract of Captain Hannay’s 1835-1836 journal appeared in several places in the late 1830s. This particular version was published in Selection of Papers Regarding the Hill Tracts Between Assam and Burmah and of the Upper Brahmaputra (Calcutta: Bengal Secretariat Press, 1873
Robust Quantum Communication Using A Polarization-Entangled Photon Pair
Noise and imperfection of realistic devices are major obstacles for
implementing quantum cryptography. In particular birefringence in optical
fibers leads to decoherence of qubits encoded in polarization of photon. We
show how to overcome this problem by doing single qubit quantum communication
without a shared spatial reference frame and precise timing. Quantum
information will be encoded in pair of photons using ``tag'' operations which
corresponds to the time delay of one of the polarization modes. This method is
robust against the phase instability of the interferometers despite the use of
time-bins. Moreover synchronized clocks are not required in the ideal situation
no photon loss case as they are only necessary to label the different encoded
qubits.Comment: 4 pages, 2 figure
Exploration of Marine Resources by Photographic Remote Sensing
The interpretation of photographs in oceanographic remote sensing is discussed. The photographs were made from spacecraft with two exceptions. Two photographs were made from aircraft. There were three types of film used to make the photographs: black-and-white, color, and color IR. Black and white photography is well known; it presents pictures in various shades of gray from black to white. Color film presents pictures in color, very nearly as the human eye sees them. Color IR film presents pictures in color also but not as seen by the human eye. Blue becomes much deeper blue, green is suppressed to some extent, and red is recorded beyond the visual range of the human eye, out in the near infrared. The most noticeable effect of the use of color IR film is that leaf materials which are highly reflective in the infrared part of the spectrum are presented as red
Unconditional Security of Three State Quantum Key Distribution Protocols
Quantum key distribution (QKD) protocols are cryptographic techniques with
security based only on the laws of quantum mechanics. Two prominent QKD schemes
are the BB84 and B92 protocols that use four and two quantum states,
respectively. In 2000, Phoenix et al. proposed a new family of three state
protocols that offers advantages over the previous schemes. Until now, an error
rate threshold for security of the symmetric trine spherical code QKD protocol
has only been shown for the trivial intercept/resend eavesdropping strategy. In
this paper, we prove the unconditional security of the trine spherical code QKD
protocol, demonstrating its security up to a bit error rate of 9.81%. We also
discuss on how this proof applies to a version of the trine spherical code QKD
protocol where the error rate is evaluated from the number of inconclusive
events.Comment: 4 pages, published versio
Self-Reported Energy Intake and Energy Expenditure in Elderly Women
The elderly are a growing population; however, limited information concerning energy requirements of the elderly is available. Dietary intake data have been collected in research and clinical settings to determine the intakes of energy and nutrients, but the accuracy of dietary intake data has been difficult to verify. Studies using doubly labeled water have suggested that dietary energy intake is underreported by obese subjects (1), adolescents (2), and athletes (3). Diet records were collected for 6 to 14 days in these studies (1), (2), (3). Elderly subjects have also underreported energy intake compared with total energy expenditure (TEE), either measured (4), (5), (6) or predicted (7). However, these studies only collected dietary data for 3 or 4 days, while energy expenditure was measured for 10 to 14 days using doubly labeled water. It is generally accepted that a major source of random variation in dietary energy can be ascribed to a person\u27s day-to-day variation in energy consumption, which averages 20% to 30% (8). This random variation decreases as the square root of the number of study days increases, such that it is approximately 10% for a 7-day record (9). Thus, some of the variability in self-reported energy intake may be attributable to the limited number of observations taken in previous studies of elderly women. To our knowledge, a comparison of TEE using doubly labeled water and concurrent diet records for a full week for elderly women has not been reported previously. The purpose of our study was to determine whether a complete recording of dietary intake would improve the accuracy of and reduce the individual variation in self-reported dietary energy intake compared with energy expenditure measurements using doubly labeled water
Robust polarization-based quantum key distribution over collective-noise channel
We present two polarization-based protocols for quantum key distribution. The
protocols encode key bits in noiseless subspaces or subsystems, and so can
function over a quantum channel subjected to an arbitrary degree of collective
noise, as occurs, for instance, due to rotation of polarizations in an optical
fiber. These protocols can be implemented using only entangled photon-pair
sources, single-photon rotations, and single-photon detectors. Thus, our
proposals offer practical and realistic alternatives to existing schemes for
quantum key distribution over optical fibers without resorting to
interferometry or two-way quantum communication, thereby circumventing,
respectively, the need for high precision timing and the threat of Trojan horse
attacks.Comment: Minor changes, added reference
Higher Security Thresholds for Quantum Key Distribution by Improved Analysis of Dark Counts
We discuss the potential of quantum key distribution (QKD) for long distance
communication by proposing a new analysis of the errors caused by dark counts.
We give sufficient conditions for a considerable improvement of the key
generation rates and the security thresholds of well-known QKD protocols such
as Bennett-Brassard 1984, Phoenix-Barnett-Chefles 2000, and the six-state
protocol. This analysis is applicable to other QKD protocols like Bennett 1992.
We examine two scenarios: a sender using a perfect single-photon source and a
sender using a Poissonian source.Comment: 6 pages, 2 figures, v2: We obtained better results by using reverse
reconciliation as suggested by Nicolas Gisi
Experimental Implementation of Discrete Time Quantum Random Walk on an NMR Quantum Information Processor
We present an experimental implementation of the coined discrete time quantum
walk on a square using a three qubit liquid state nuclear magnetic resonance
(NMR) quantum information processor (QIP). Contrary to its classical
counterpart, we observe complete interference after certain steps and a
periodicity in the evolution. Complete state tomography has been performed for
each of the eight steps making a full period. The results have extremely high
fidelity with the expected states and show clearly the effects of quantum
interference in the walk. We also show and discuss the importance of choosing a
molecule with a natural Hamiltonian well suited to NMR QIP by implementing the
same algorithm on a second molecule. Finally, we show experimentally that
decoherence after each step makes the statistics of the quantum walk tend to
that of the classical random walk.Comment: revtex4, 8 pages, 6 figures, submitted to PR
Ability of LISA to detect a gravitational-wave background of cosmological origin: The cosmic string case
We investigate the ability of the Laser Interferometer Space Antenna (LISA) to detect a stochastic gravitational-wave background (GWB) produced by cosmic strings, and to subsequently estimate the string tension
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in the presence of instrument noise, an astrophysical background from compact binaries, and the galactic foreground from white dwarf binaries. Fisher Information and Markov Chain Monte Carlo methods provide estimates of the LISA noise and the parameters for the different signal sources. We demonstrate the importance of including the galactic foreground as well as the astrophysical background for LISA to detect a cosmic string produced GWB and estimate the string tension. Considering the expected astrophysical background and a galactic foreground, a cosmic string tension in the
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to
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range or bigger could be measured by LISA, with the galactic foreground affecting this limit more than the astrophysical background. The parameter estimation methods presented here can be applied to other cosmological backgrounds in the LISA observation band
Experimental Quantum Communication without a Shared Reference Frame
We present an experimental realization of a robust quantum communication
scheme [Phys. Rev. Lett. 93, 220501 (2004)] using pairs of photons entangled in
polarization and time. Our method overcomes errors due to collective rotation
of the polarization modes (e.g., birefringence in optical fiber or
misalignment), is insensitive to the phase's fluctuation of the interferometer,
and does not require any shared reference frame including time reference,
except the need to label different photons. The practical robustness of the
scheme is further shown by implementing a variation of the Bennett-Brassard
1984 quantum key distribution protocol over 1 km optical fiber.Comment: 4 pages, 4 figure
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