1,720,996 research outputs found
Meson-Exchange Current in One- and Two-Nucleon Emission Induced by Electromagnetic Probes
No full textA bird's eye view of quantum computers
No full textQuantum computers are discussed in the general framework of computation, the
laws of physics and the foundations of quantum mechanics
Optimal purification of a generic n-qudit state
No full textWe propose a quantum algorithm for the purification of a generic mixed state rho of a n-qudit system by using an ancillary n-qudit system. The algorithm is optimal in that (i) the number of ancillary qudits cannot be reduced, (ii) the number of parameters which determine the purification state | Psi > exactly equals the number of degrees of freedom of rho , and (iii) | Psi > is easily determined from the density matrix rho . Moreover, we introduce a quantum circuit in which the quantum gates are unitary transformations acting on a 2n-qudit system. These transformations are determined by parameters that can be tuned to generate, once the ancillary qudits are disregarded, any given mixed n-qudit state
Simple representation of quantum process tomography
No full textWe show that the Fano representation leads to a particularly simple and appealing form of the quantum
process tomography matrix [chi]F, in that the matrix [chi]F is real, the number of matrix elements is exactly equal to
the number of free parameters required for the complete characterization of a quantum operation, and these
matrix elements are directly related to evolution of the expectation values of the system's polarization measurements.
These facts are illustrated in the examples of one- and two-qubit quantum noise channel
Gaussian wave packets in phase space: The Fermi g(F) function
No full textA pure quantum state can be equivalently represented by means of its wave function psi(q) or by the Fermi function g(F)(q,p), with q and p coordinates and conjugate momenta of the system of interest. We show that a Gaussian wave packet can be conveniently visualized in phase space by the curve g(F)(q,p)=0. The change in time of the g(F)=0 curve is calculated for a Gaussian packet evolving freely or under a constant or a harmonic force, and the spreading or shrinking of the packet is easily interpreted in phase space. We also discuss a gedanken prism microscope experiment for measuring the position-momentum correlation. This gedanken experiment, together with the well-known Heisenberg microscope and von Neumann velocimeter, is sufficient to fully determine the state of a Gaussian packet
Entanglement computation in atoms and molecules
No full textIn this paper, a method for computing entanglement of electrons in atoms and molecules is described.
The importance of entanglement computation for Quantum Computers and for Biology is highlighted and the existing models’ pros and cons are illustrated. A description of the
algorithms follows, with some considerations about the execution times and how they scale increasing the system’s Hilbert space dimension
Quantum simulation of the single-particle Schrodinger equation
No full textThe nature of a quantum computer is described in the concrete context of a quantum simulator of the single-particle Schrodinger equation. We show that a register of 6-10 qubits is sufficient to realize a useful quantum simulator capable of efficiently solving standard quantum mechanical problem
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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