54,645 research outputs found
Bounds on Quantum Multiple-Parameter Estimation with Gaussian State
We investigate the quantum Cramer-Rao bounds on the joint multiple-parameter
estimation with the Gaussian state as a probe. We derive the explicit right
logarithmic derivative and symmetric logarithmic derivative operators in such a
situation. We compute the corresponding quantum Fisher information matrices,
and find that they can be fully expressed in terms of the mean displacement and
covariance matrix of the Gaussian state. Finally, we give some examples to show
the utility of our analytical results.Comment: 7 pages, 5 figure
Giant Halos in Dwarf Irregular Galaxies vs. Dwarf Elliptical Galaxies
We present a discovery of a giant stellar halo in NGC 6822, a dwarf irregular
galaxy in the Local Group. This halo is mostly made of old red giants, showing
striking features: 1) it is several times larger than the main body of the
galaxy seen in the optical images, and 2) it is elongated in the direction
almost perpendicular to the HI disk of NGC 6822. The structure of this stellar
halo looks similar to the shape of dwarf elliptical galaxies, indicating that
the halos of dwarf irregular galaxies share the same origin with those of the
dwarf elliptical galaxies.Comment: 4 pages, 3 figures, proceedings of IAU Colloquium 198, "Near-Field
Cosmology With Dwarf Elliptical Galaxies", editors H. Jerjen and B. Binggeli,
Cambridge University Pres
Moisture-triggered physically transient electronics
Physically transient electronics, a form of electronics that can physically disappear in a controllable manner, is very promising for emerging applications. Most of the transient processes reported so far only occur in aqueous solutions or biofluids, offering limited control over the triggering and degradation processes. We report novel moisture-triggered physically transient electronics, which exempt the needs of resorption solutions and can completely disappear within well-controlled time frames. The triggered transient process starts with the hydrolysis of the polyanhydride substrate in the presence of trace amounts of moisture in the air, a process that can generate products of corrosive organic acids to digest various inorganic electronic materials and components. Polyanhydride is the only example of polymer that undergoes surface erosion, a distinct feature that enables stable operation of the functional devices over a predefined time frame. Clear advantages of this novel triggered transience mode include that the lifetime of the devices can be precisely controlled by varying the moisture levels and changing the composition of the polymer substrate. The transience time scale can be tuned from days to weeks. Various transient devices, ranging from passive electronics (such as antenna, resistor, and capacitor) to active electronics ( such as transistor, diodes, optoelectronics, and memories), and an integrated system as a platform demonstration have been developed to illustrate the concept and verify the feasibility of this design strategy
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