2,215 research outputs found
Floodlight Quantum Key Distribution: A Practical Route to Gbps Secret-Key Rates
The channel loss incurred in long-distance transmission places a significant
burden on quantum key distribution (QKD) systems: they must defeat a passive
eavesdropper who detects all the light lost in the quantum channel and does so
without disturbing the light that reaches the intended destination. The current
QKD implementation with the highest long-distance secret-key rate meets this
challenge by transmitting no more than one photon per bit [Opt. Express 21,
24550-24565 (2013)]. As a result, it cannot achieve the Gbps secret-key rate
needed for one-time pad encryption of large data files unless an impractically
large amount of multiplexing is employed. We introduce floodlight QKD (FL-QKD),
which floods the quantum channel with a high number of photons per bit
distributed over a much greater number of optical modes. FL-QKD offers security
against the optimum frequency-domain collective attack by transmitting less
than one photon per mode and using photon-coincidence channel monitoring, and
it is completely immune to passive eavesdropping. More importantly, FL-QKD is
capable of a 2 Gbps secret-key rate over a 50 km fiber link, without any
multiplexing, using available equipment, i.e., no new technology need be
developed. FL-QKD achieves this extraordinary secret-key rate by virtue of its
unprecedented secret-key efficiency, in bits per channel use, which exceeds
those of state-of-the-art systems by two orders of magnitude.Comment: 18 pages, 5 figure
Using the GrassGro Decision Support Tool to Evaluate the Response in Grazing Systems to Pasture Legume or a Grass Cultivar With Improved Nutritive Value
Decision support tools (DST) based on models of grazing systems allow the evaluation of changes in enterprise management on productivity and profitability. The Grassgro DST (Moore et al., 1997) uses historical weather data on a daily time step to simulate pasture growth and the resultant productivity of either grazing sheep or cattle. Different pasture species are represented within a parameter set that describes the response of pasture species to their environment. Manipulation of these parameters provides a means of evaluating, a priori, the likely responses of livestock production to ‘improved cultivars’. We report the results of simulations conducted within grazing enterprises at three locations in southern Australia: a breeding ewe enterprise at Benalla; a wool-producing enterprise at Hamilton; and a beef breeding enterprise at Corryong
Using Cuticular Wax Alkanes and Computer Simulation to Estimate Diet Selection, Herbage Intake and Nutrient Cycling in Grazing Sheep
In grazing ewes, plant cuticular wax alkanes were used as markers to estimate diet selection, herbage intake, N intake and N excretion in faeces. Pasture and animal data were then used as inputs to the decision-support system GrazFeed, which simulates grazing and digestion to predict herbage intake, N intake and N excretion. Estimated and predicted intakes agreed closely, especially for N intake, and it is concluded that, subject to further investigation of the possibility that GrazFeed slightly under-estimated faecal N excretion, the close agreement between estimated and predicted OM and N intakes suggests that this combined use of alkane methods and simulation could provide a simple means of estimating the urinary return of N or other nutrients to pasture
Simulation study of pressure and temperature dependence of the negative thermal expansion in Zn(CN)(2)
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Failure mechanisms of graphene under tension
Recent experiments established pure graphene as the strongest material known
to mankind, further invigorating the question of how graphene fails. Using
density functional theory, we reveal the mechanisms of mechanical failure of
pure graphene under a generic state of tension. One failure mechanism is a
novel soft-mode phonon instability of the -mode, whereby the graphene
sheet undergoes a phase transition and is driven towards isolated benzene rings
resulting in a reduction of strength. The other is the usual elastic
instability corresponding to a maximum in the stress-strain curve. Our results
indicate that finite wave vector soft modes can be the key factor in limiting
the strength of monolayer materials
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