83,249 research outputs found
A Multisection Broadband Impedance Transforming Branch-Line Hybrid
Measurements and design equations for a two section impedance transforming
hybrid suitable for MMIC applications and a new method of synthesis for
multisection branch-line hybrids are reported. The synthesis method allows the
response to be specified either of Butterworth or Chebyshev type. Both
symmetric (with equal input and output impedances) and non-symmetric (impedance
transforming) designs are feasible. Starting from a given number of sections,
type of response, and impedance transformation ratio and for a specified
midband coupling, power division ratio, isolation or directivity ripple
bandwidth, the set of constants needed for the evaluation of the reflection
coefficient response is first calculated. The latter is used to define a
driving point impedance of the circuit, synthesize it and obtain the branch
line immittances with the use of the concept of double length unit elements
(DLUE). The experimental results obtained with microstrip hybrids constructed
to test the validity of the brute force optimization and the synthesized
designs show very close agreement with the computed responses.Comment: 6 pages and 14 figures. Published in IEEE Transactions on Microwave
Theory and Technique
NMR investigation of contextuality in a quantum harmonic oscillator via pseudospin mapping
Physical potentials are routinely approximated to harmonic potentials so as
to analytically solve the system dynamics. Often it is important to know when a
quantum harmonic oscillator (QHO) behaves quantum mechanically and when
classically. Recently Su et. al. [Phys. Rev. A {\bf 85}, 052126 (2012)] have
theoretically shown that QHO exhibits quantum contextuality (QC) for a certain
set of pseudospin observables. In this work, we encode the four eigenstates of
a QHO onto four Zeeman product states of a pair of spin-1/2 nuclei. Using the
techniques of NMR quantum information processing, we then demonstrate the
violation of a state-dependent inequality arising from the noncontextual hidden
variable model, under specific experimental arrangements. We also
experimentally demonstrate the violation of a state-independent inequality by
thermal equilibrium states of nuclear spins, thereby assessing their
quantumness.Comment: 5 Pages, 3 Figures, context dependency illustrated, error below eq. 5
correcte
Efficient Quantum State Tomography for Quantum Information Processing using a two-dimensional Fourier Transform Technique
A new method of quantum state tomography for quantum information processing
is described. The method based on two-dimensional Fourier transform technique
involves detection of all the off-diagonal elements of the density matrix in a
two-dimensional experiment. All the diagonal elements are detected in another
one-dimensional experiment. The method is efficient and applicable to a wide
range of spin systems. The proposed method is explained using a 2 qubit system
and demonstrated by tomographing arbitrary complex density matrices of 2 and 4
qubit systems using simulations.Comment: 11 pages and 2 figure
A Channel Coding Perspective of Collaborative Filtering
We consider the problem of collaborative filtering from a channel coding
perspective. We model the underlying rating matrix as a finite alphabet matrix
with block constant structure. The observations are obtained from this
underlying matrix through a discrete memoryless channel with a noisy part
representing noisy user behavior and an erasure part representing missing data.
Moreover, the clusters over which the underlying matrix is constant are {\it
unknown}. We establish a sharp threshold result for this model: if the largest
cluster size is smaller than (where the rating matrix is of size
), then the underlying matrix cannot be recovered with any
estimator, but if the smallest cluster size is larger than , then
we show a polynomial time estimator with diminishing probability of error. In
the case of uniform cluster size, not only the order of the threshold, but also
the constant is identified.Comment: 32 pages, 1 figure, Submitted to IEEE Transactions on Information
Theor
- …