44,230 research outputs found
Marginal distributions in -dimensional phase space and the quantum marginal theorem
We study the problem of constructing a probability density in 2N-dimensional
phase space which reproduces a given collection of joint probability
distributions as marginals. Only distributions authorized by quantum mechanics,
i.e. depending on a (complete) commuting set of variables, are considered.
A diagrammatic or graph theoretic formulation of the problem is developed. We
then exactly determine the set of ``admissible'' data, i.e. those types of data
for which the problem always admits solutions. This is done in the case where
the joint distributions originate from quantum mechanics as well as in the case
where this constraint is not imposed. In particular, it is shown that a
necessary (but not sufficient) condition for the existence of solutions is
. When the data are admissible and the quantum constraint is not
imposed, the general solution for the phase space density is determined
explicitly. For admissible data of a quantum origin, the general solution is
given in certain (but not all) cases. In the remaining cases, only a subset of
solutions is obtained.Comment: 29 pages (Work supported by the Indo-French Centre for the Promotion
of Advanced Research, Project Nb 1501-02). v2 to add a report-n
Integrated atomistic process and device simulation of decananometre MOSFETs
In this paper we present a methodology for the integrated atomistic process and device simulation of decananometre MOSFETs. The atomistic process simulations were carried out using the kinetic Monte Carlo process simulator DADOS, which is now integrated into the Synopsys 3D process and device simulation suite Taurus. The device simulations were performed using the Glasgow 3D statistical atomistic simulator, which incorporates density gradient quantum corrections. The overall methodology is illustrated in the atomistic process and device simulation of a well behaved 35 nm physical gate length MOSFET reported by Toshiba
Position Dependent Mass Schroedinger Equation and Isospectral Potentials : Intertwining Operator approach
Here we have studied first and second-order intertwining approach to generate
isospectral partner potentials of position-dependent (effective) mass
Schroedinger equation. The second-order intertwiner is constructed directly by
taking it as second order linear differential operator with position depndent
coefficients and the system of equations arising from the intertwining
relationship is solved for the coefficients by taking an ansatz. A complete
scheme for obtaining general solution is obtained which is valid for any
arbitrary potential and mass function. The proposed technique allows us to
generate isospectral potentials with the following spectral modifications: (i)
to add new bound state(s), (ii) to remove bound state(s) and (iii) to leave the
spectrum unaffected. To explain our findings with the help of an illustration,
we have used point canonical transformation (PCT) to obtain the general
solution of the position dependent mass Schrodinger equation corresponding to a
potential and mass function. It is shown that our results are consistent with
the formulation of type A N-fold supersymmetry [14,18] for the particular case
N = 1 and N = 2 respectively.Comment: Some references have been adde
Secure, performance-oriented data management for nanoCMOS electronics
The EPSRC pilot project Meeting the Design Challenges of nanoCMOS Electronics (nanoCMOS) is focused upon delivering a production level e-Infrastructure to meet the challenges facing the semiconductor industry in dealing with the next generation of ‘atomic-scale’ transistor devices. This scale means that previous assumptions on the uniformity of transistor devices in electronics circuit and systems design are no longer valid, and the industry as a whole must deal with variability throughout the design process. Infrastructures to tackle this problem must provide seamless access to very large HPC resources for computationally expensive simulation of statistic ensembles of microscopically varying physical devices, and manage the many hundreds of thousands of files and meta-data associated with these simulations. A key challenge in undertaking this is in protecting the intellectual property associated with the data, simulations and design process as a whole. In this paper we present the nanoCMOS infrastructure and outline an evaluation undertaken on the Storage Resource Broker (SRB) and the Andrew File System (AFS) considering in particular the extent that they meet the performance and security requirements of the nanoCMOS domain. We also describe how metadata management is supported and linked to simulations and results in a scalable and secure manner
Two photon annihilation operators and squeezed vacuum
Inverses of the harmonic oscillator creation and annihilation operators by their actions on the number states are introduced. Three of the two photon annihilation operators, viz., a(sup +/-1)a, aa(sup +/-1), and a(sup 2), have normalizable right eigenstates with nonvanishing eigenvalues. The eigenvalue equation of these operators are discussed and their normalized eigenstates are obtained. The Fock state representation in each case separates into two sets of states, one involving only the even number states while the other involving only the odd number states. It is shown that the even set of eigenstates of the operator a(sup +/-1)a is the customary squeezed vacuum S(sigma) O greater than
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