7,750 research outputs found
Compressed Sensing Based on Random Symmetric Bernoulli Matrix
The task of compressed sensing is to recover a sparse vector from a small
number of linear and non-adaptive measurements, and the problem of finding a
suitable measurement matrix is very important in this field. While most recent
works focused on random matrices with entries drawn independently from certain
probability distributions, in this paper we show that a partial random
symmetric Bernoulli matrix whose entries are not independent, can be used to
recover signal from observations successfully with high probability. The
experimental results also show that the proposed matrix is a suitable
measurement matrix.Comment: arXiv admin note: text overlap with arXiv:0902.4394 by other author
Minimal sets determining universal and phase-covariant quantum cloning
We study the minimal input sets which can determine completely the universal
and the phase-covariant quantum cloning machines. We find that the universal
quantum cloning machine, which can copy arbitrary input qubit equally well,
however can be determined completely by only four input states located at the
four vertices of a tetrahedron. The phase-covariant quantum cloning machine,
which can copy all qubits located on the equator of the Bloch sphere, can be
determined by three equatorial qubits with equal angular distance. These
results sharpen further the well-known results that BB84 states and six-states
used in quantum cryptography can determine completely the phase-covariant and
universal quantum cloning machines. This concludes the study of the power of
universal and phase-covariant quantum cloning, i.e., from minimal input sets
necessarily to full input sets by definition. This can simplify dramatically
the testing of whether the quantum clone machines are successful or not, we
only need to check that the minimal input sets can be cloned optimally.Comment: 7 pages, 4 figure
Ultrathin Acoustic Parity-Time Symmetric Metasurface Cloak
Invisibility or unhearability cloaks have beenmade possible by using metamaterials enabling light or sound to flow around obstacle
without the trace of reflections or shadows. Metamaterials are known for being flexible building units that can mimic a host of
unusual and extreme material responses, which are essential when engineering artificial material properties to realize a coordinate
transforming cloak. Bending and stretching the coordinate grid in space require stringent material parameters; therefore, small
inaccuracies and inevitablematerial losses become sources for unwanted scattering that are decremental to the desired effect.These
obstacles further limit the possibility of achieving a robust concealment of sizeable objects from either radar or sonar detection. By
using an elaborate arrangement of gain and lossy acousticmedia respecting parity-time symmetry, we built a one-way unhearability
cloak able to hide objects seven times larger than the acoustic wavelength. Generally speaking, our approach has no limits in terms
of working frequency, shape, or size, specifically though we demonstrate how, in principle, an object of the size of a human can be
hidden from audible sound
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