23,373 research outputs found
An Online Parallel and Distributed Algorithm for Recursive Estimation of Sparse Signals
In this paper, we consider a recursive estimation problem for linear
regression where the signal to be estimated admits a sparse representation and
measurement samples are only sequentially available. We propose a convergent
parallel estimation scheme that consists in solving a sequence of
-regularized least-square problems approximately. The proposed scheme
is novel in three aspects: i) all elements of the unknown vector variable are
updated in parallel at each time instance, and convergence speed is much faster
than state-of-the-art schemes which update the elements sequentially; ii) both
the update direction and stepsize of each element have simple closed-form
expressions, so the algorithm is suitable for online (real-time)
implementation; and iii) the stepsize is designed to accelerate the convergence
but it does not suffer from the common trouble of parameter tuning in
literature. Both centralized and distributed implementation schemes are
discussed. The attractive features of the proposed algorithm are also
numerically consolidated.Comment: Part of this work has been presented at The Asilomar Conference on
Signals, Systems, and Computers, Nov. 201
Efficient Quantum Compression for Ensembles of Identically Prepared Mixed States
We present one-shot compression protocols that optimally encode ensembles of
identically prepared mixed states into qubits. In contrast to
the case of pure-state ensembles, we find that the number of encoding qubits
drops down discontinuously as soon as a nonzero error is tolerated and the
spectrum of the states is known with sufficient precision. For qubit ensembles,
this feature leads to a 25% saving of memory space. Our compression protocols
can be implemented efficiently on a quantum computer.Comment: 5+19 pages, 2 figures. Published versio
The longitudinal response function of the deuteron in chiral effective field theory
We use chiral effective field theory (EFT) to make predictions for the
longitudinal electromagnetic response function of the deuteron, f_L, which is
measured in d(e,e'N) reactions. In this case the impulse approximation gives
the full chiral EFT result up to corrections that are of O(P^4) relative to
leading. By varying the cutoff in the chiral EFT calculations between 0.6 and 1
GeV we conclude that the calculation is accurate to better than 10 % for values
of q^2 within 4 fm^{-2} of the quasi-free peak, up to final-state energies
E_{np}=60 MeV. In these regions chiral EFT is in reasonable agreement with
predictions for f_L obtained using the Bonn potential. We also find good
agreement with existing experimental data on f_L, albeit in a more restricted
kinematic domain.Comment: 33 pages, 10 figures. Accepted for publication in EPJA, with a few
further correction
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