1,103 research outputs found
Approach to accurately measuring the speed of optical precursors
Precursors can serve as a bound on the speed of information with dispersive
medium. We propose a method to identify the speed of optical precursors using
polarization-based interference in a solid-state device, which can bound the
accuracy of the precursors' speed to less than with conventional
experimental conditions. Our proposal may have important implications for
optical communications and fast information processing.Comment: 4 pages, 4 figure
Probabilistic teleportation and entanglement matching
Teleportation may be taken as sending and extracting quantum information
through quantum channels. In this report, it is shown that to get the maximal
probability of exact teleportation through partially entangled quantum
channels, the sender (Alice) need only to operate a measurement which satisfy
an ``entanglement matching'' to this channel. An optimal strategy is also
provided for the receiver (Bob) to extract the quantum information by adopting
general evolutions.Comment: 3.5 pages, No figure
A novel quantum key distribution scheme with orthogonal product states
The general conditions for the orthogonal product states of the multi-state
systems to be used in quantum key distribution (QKD) are proposed, and a novel
QKD scheme with orthogonal product states in the 3x3 Hilbert space is
presented. We show that this protocol has many distinct features such as great
capacity, high efficiency. The generalization to nxn systems is also discussed
and a fancy limitation for the eavesdropper's success probability is reached.Comment: 4 Pages, 3 Figure
Optical realization of universal quantum cloning
Beyond the no-cloning theorem, the universal symmetric quantum cloning
machine was first addressed by Buzek and Hillery. Here, we realized the
one-to-two qubits Buzek-Hillery cloning machine with linear optical devices.
This method relies on the representation of several qubits by a single photon.
We showed that, the fidelities between the two output qubits and the original
qubit are both 5/6 (which proved to be the optimal fidelity of one-to-two
qubits universal cloner) for arbitrary input pure states.Comment: 5 Pages, 2 Figure
Probabilistic quantum cloning via Greenberger-Horne-Zeilinger states
We propose a probabilistic quantum cloning scheme using
Greenberger-Horne-Zeilinger states, Bell basis measurements, single-qubit
unitary operations and generalized measurements, all of which are within the
reach of current technology. Compared to another possible scheme via Tele-CNOT
gate [D. Gottesman and I. L. Chuang, Nature 402, 390 (1999)], the present
scheme may be used in experiment to clone the states of one particle to those
of two different particles with higher probability and less GHZ resources.Comment: 8 Pages, 4 Figures, final version to appear in PR
Managing the development of the Wide-field Infrared Survey Explorer mission
The Wide-field Infrared Survey Explorer (WISE), a NASA Medium-Class Explorer (MIDEX) mission, is surveying the entire sky in four bands from 3.4 to 22 microns with a sensitivity hundreds to hundreds of thousands times better than previous all-sky surveys at these wavelengths. The single WISE instrument consists of a 40 cm three-mirror anastigmatic telescope, a two-stage solid hydrogen cryostat, a scan mirror mechanism, and reimaging optics giving 6" resolution (fullwidth- half-maximum). WISE was placed into a Sun-synchronous polar orbit on a Delta II 7320 launch vehicle on December 14, 2009. NASA selected WISE as a MIDEX in 2002 following a rigorous competitive selection process. To gain further confidence in WISE, NASA extended the development period one year with an option to cancel the mission if certain criteria were not met. MIDEX missions are led by the principal investigator who in this case delegated day-today management to the project manager. With a cost cap and relatively short development schedule, it was essential for all WISE partners to work seamlessly together. This was accomplished with an integrated management team representing all key partners and disciplines. The project was developed on budget and on schedule in spite of the need to surmount significant technical challenges. This paper describes our management approach, key challenges and critical decisions made. Results are described from a programmatic, technical and scientific point of view. Lessons learned are offered for projects of this type
Monte-Carlo simulations of the recombination dynamics in porous silicon
A simple lattice model describing the recombination dynamics in visible light
emitting porous Silicon is presented. In the model, each occupied lattice site
represents a Si crystal of nanometer size. The disordered structure of porous
Silicon is modeled by modified random percolation networks in two and three
dimensions. Both correlated (excitons) and uncorrelated electron-hole pairs
have been studied. Radiative and non-radiative processes as well as hopping
between nearest neighbor occupied sites are taken into account. By means of
extensive Monte-Carlo simulations, we show that the recombination dynamics in
porous Silicon is due to a dispersive diffusion of excitons in a disordered
arrangement of interconnected Si quantum dots. The simulated luminescence decay
for the excitons shows a stretched exponential lineshape while for uncorrelated
electron-hole pairs a power law decay is suggested. Our results successfully
account for the recombination dynamics recently observed in the experiments.
The present model is a prototype for a larger class of models describing
diffusion of particles in a complex disordered system.Comment: 33 pages, RevTeX, 19 figures available on request to
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