4,599 research outputs found
Practical quantum key distribution over a 48-km optical fiber network
The secure distribution of the secret random bit sequences known as "key"
material, is an essential precursor to their use for the encryption and
decryption of confidential communications. Quantum cryptography is a new
technique for secure key distribution with single-photon transmissions:
Heisenberg's uncertainty principle ensures that an adversary can neither
successfully tap the key transmissions, nor evade detection (eavesdropping
raises the key error rate above a threshold value). We have developed
experimental quantum cryptography systems based on the transmission of
non-orthogonal photon states to generate shared key material over
multi-kilometer optical fiber paths and over line-of-sight links. In both
cases, key material is built up using the transmission of a single-photon per
bit of an initial secret random sequence. A quantum-mechanically random subset
of this sequence is identified, becoming the key material after a data
reconciliation stage with the sender. Here we report the most recent results of
our optical fiber experiment in which we have performed quantum key
distribution over a 48-km optical fiber network at Los Alamos using photon
interference states with the B92 and BB84 quantum key distribution protocols.Comment: 13 pages, 7 figures, .pdf format submitted to Journal of Modern
Optic
Boundary layer blockage in expansion tube nozzles
The results of a first order perfect gas correction for the effects of the boundary layer formation within expansion tubes with nozzles are presented. The analytical model developed to describe the boundary layer formation within the expansion tube and an expansion nozzle located at the end of the acceleration tube is based on the Karman integral equations. The results of this analytical model are compared with experimental data from an expansion diffuser. The model provides a useful tool for the preliminary design of nozzles for such facilities
Vaterite Dissolution: Mechanism and Kinetics
The dissolution of porous spherulitic, vaterite particles in aqueous solution is investigated via microscopic monitoring of their size as a function of time. The latter is shown to provide a clear, generic distinction between dissolution controlled either by the rate of a surface-controlled reaction or via dissolution under conditions where the concentration of calcium and carbonate ions is pinned locally by the solubility product of vaterite followed by diffusion away from the dissolving interface into the bulk solution. Dissolution under “thermodynamic control” is shown to be the case for vaterite particles, allowing a value of the solubility product to be determined in the light of the known solution phase equilibria, including the ion pairs CaCO3, CaOH+, and CaHCO3 +
The Role of Citizen Science and Volunteer Data Collection in Zoological Research
In many ways, science has never been as popular as it is now. With an ever-increasing number of popular science books on everything from astronomy to climate change and evolution and entire TV channels devoted to science output, the public seems spoilt for choice. However, paradoxically, there is also an increasing disconnect between science—and scientists—and society, and this is certainly evident in the life sciences. This disconnect comes in two forms: interest and level of knowledge. Indeed, one has only to look at the 2012 US presidential election campaign to see the lack of scientific knowledge possessed by many of the political elite about topics such as climate change. If high profile scientific topics are still so widely misunderstood by those in the public eye, it is unsurprising that there is such a lack of understanding of, and interest in, scientific topics in the general public. It should, in theory, be the easiest to address this discontent in subjects like zoology, where the evidence is all around us and can be easily seen, appreciated, and studied by the world’s citizens
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