701 research outputs found
Computer graphics data conditioning
Graphics data conditioning program expedites engineering analysis of flight data and ensures timely correction of measurement errors. By adding interactive computer graphic displays to existing data conditioning programs, computational results are immediately visible, enabling on-line intervention and control of computer processing
Quantum cooling and squeezing of a levitating nanosphere via time-continuous measurements
With the purpose of controlling the steady state of a dielectric nanosphere
levitated within an optical cavity, we study its conditional dynamics under
simultaneous sideband cooling and additional time-continuous measurement of
either the output cavity mode or the nanosphere's position. We find that the
average phonon number, purity and quantum squeezing of the steady-states can
all be made more non-classical through the addition of time-continuous
measurement. We predict that the continuous monitoring of the system, together
with Markovian feedback, allows one to stabilize the dynamics for any value of
the laser frequency driving the cavity. By considering state-of-the-art values
of the experimental parameters, we prove that one can in principle obtain a
non-classical (squeezed) steady-state with an average phonon number .Comment: 10 pages, 9 figures; v2: close to published versio
Cavity cooling a single charged nanoparticle
The development of laser cooling coupled with the ability to trap atoms and
ions in electromagnetic fields, has revolutionised atomic and optical physics,
leading to the development of atomic clocks, high-resolution spectroscopy and
applications in quantum simulation and processing. However, complex systems,
such as large molecules and nanoparticles, lack the simple internal resonances
required for laser cooling. Here we report on a hybrid scheme that uses the
external resonance of an optical cavity, combined with radio frequency (RF)
fields, to trap and cool a single charged nanoparticle. An RF Paul trap allows
confinement in vacuum, avoiding instabilities that arise from optical fields
alone, and crucially actively participates in the cooling process. This system
offers great promise for cooling and trapping a wide range of complex charged
particles with applications in precision force sensing, mass spectrometry,
exploration of quantum mechanics at large mass scales and the possibility of
creating large quantum superpositions.Comment: 8 pages, 5 figures Updated version includes additional references,
new title, and supplementary information include
Optomechanical cooling of levitated spheres with doubly-resonant fields
Optomechanical cooling of levitated dielectric particles represents a
promising new approach in the quest to cool small mechanical resonators towards
their quantum ground state. We investigate two-mode cooling of levitated
nanospheres in a self-trapping regime. We identify a rich structure of split
sidebands (by a mechanism unrelated to usual strong-coupling effects) and
strong cooling even when one mode is blue detuned. We show the best regimes
occur when both optical fields cooperatively cool and trap the nanosphere,
where cooling rates are over an order of magnitude faster compared to
corresponding single-sideband cooling rates.Comment: 8 Pages, 7 figure
Proof Theory, Transformations, and Logic Programming for Debugging Security Protocols
We define a sequent calculus to formally specify, simulate, debug and verify security protocols. In our sequents we distinguish between the current knowledge of principals and the current global state of the session. Hereby, we can describe the operational semantics of principals and of an intruder in a simple and modular way. Furthermore, using proof theoretic tools like the analysis of permutability of rules, we are able to find efficient proof strategies that we prove complete for special classes of security protocols including Needham-Schroeder. Based on the results of this preliminary analysis, we have implemented a Prolog meta-interpreter which allows for rapid prototyping and for checking safety properties of security protocols, and we have applied it for finding error traces and proving correctness of practical examples
Deduction with XOR Constraints in Security API Modelling
We introduce XOR constraints, and show how they enable a theorem prover to reason effectively about security critical subsystems which employ bitwise XOR. Our primary case study is the API of the IBM 4758 hardware security module. We also show how our technique can be applied to standard security protocols
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