Search results for "Computation"
showing 10 items of 7362 documents
The re Structure of Cyclopropane
2000
A long-standing controversy regarding the re structure of cyclopropane is resolved by performing high-level quantum chemical calculations and analyzing the experimental rotational constants for C3H6 and C3H4D2 augmented by calculated vibrational corrections. For the latter, a least-squares fit yields the following set of parameters: re (CC) = 1.5030(10) A, re(CH) = 1.0786(10) A, and αe(HCH) = 114.97(10)°, which compare favorably with both the pure computational result obtained at the CCSD(T)/cc-pVQZ level as well as an earlier estimate of the re structure of cyclopropane based on analysis of gas-phase electron diffraction data. Our results are in rather poor agreement with a structure base…
Lattice quantum hadrodynamics on a CRAY Y-MP
1992
Quantum corrections to the mean-field equation of state for nuclear matter are estimated in a lattice simulation of quantum hadrodynamics on a CRAY Y-MP. In contrast with lattice quantum chromodynamics, where coordinate space methods are the standard, the calculations are carried out in momentum space and on nonhypercubic (irregular) lattices. The quantum corrections to the known, mean-field equation of state were found to be considerable. The time frame of the project and the large computational needs of the program required the use of powerful supercomputers, like the CRAY Y-MP, which are capable of performing at a very high computing speed by using both vector and parallel hardware, the …
Top-pair forward-backward asymmetry beyond next-to-leading order
2011
We make use of recent results in effective theory and higher-order perturbative calculations to improve the theoretical predictions of the QCD contribution to the top-quark pair production forward-backward asymmetry at the Tevatron. In particular, we supplement the fixed-order next-to-leading order calculation with higher-order corrections from soft-gluon resummation at next-to next-to-leading order accuracy performed in two different kinematic schemes, which allows us to make improved predictions for the asymmetry in the $p\overline{p}$ and $t\overline{t}$ rest frames as a function of the rapidity and invariant mass of the $t\overline{t}$ pair. Furthermore, we provide binned results which …
Quantum loops in the Resonance Chiral Theory: improving the vector form factor
2006
Quantum loops in the Resonance Chiral Theory are needed to improve the implementation of non-perturbative QCD. Furthermore, the one-loop computations can predict chiral low-energy couplings at next-to-leading order, a very appealing task. We present a first calculation of the vector form factor of the pion at subleading order in the 1/N_C expansion. From the analysis of the result at large energies we justify the requirement of considering short-distance constraints from form factors with resonances in the final state. The long-distance limit of our results allows to get a next-to-leading order estimate of \ell_6.
Bottom-quark mass from finite energy QCD sum rules
2011
Finite energy QCD sum rules involving both inverse and positive moment integration kernels are employed to determine the bottom quark mass. The result obtained in the $\bar{\text {MS}}$ scheme at a reference scale of $10\, {GeV}$ is $\bar{m}_b(10\,\text{GeV})= 3623(9)\,\text{MeV}$. This value translates into a scale invariant mass $\bar{m}_b(\bar{m}_b) = 4171 (9)\, {MeV}$. This result has the lowest total uncertainty of any method, and is less sensitive to a number of systematic uncertainties that affect other QCD sum rule determinations.
Entanglement replication in driven-dissipative many body systems
2012
We study the dissipative dynamics of two independent arrays of many-body systems, locally driven by a common entangled field. We show that in the steady state the entanglement of the driving field is reproduced in an arbitrarily large series of inter-array entangled pairs over all distances. Local nonclassical driving thus realizes a scale-free entanglement replication and long-distance entanglement distribution mechanism that has immediate bearing on the implementation of quantum communication networks.
Classical and quantum vortex leapfrogging in two-dimensional channels
2020
The leapfrogging of coaxial vortex rings is a famous effect which has been noticed since the times of Helmholtz. Recent advances in ultra-cold atomic gases show that the effect can now be studied in quantum fluids. The strong confinement which characterizes these systems motivates the study of leapfrogging of vortices within narrow channels. Using the two-dimensional point vortex model, we show that in the constrained geometry of a two-dimensional channel the dynamics is richer than in an unbounded domain: alongsize the known regimes of standard leapfrogging and the absence of it, we identify new regimes of backward leapfrogging and periodic orbits. Moreover, by solving the Gross-Pitaevskii…
Indistinguishability as a quantum information resource by localized measurements
2019
Quantum networks are typically made of identical subsystems. Exploiting indistinguishability as a direct quantum resource would thus be highly desirable. We show this is achievable by spatially localized measurements, enabling teleportation and entanglement swapping protocols.
On-chip generation of high-dimensional entangled quantum states and their coherent control
2017
Optical quantum states based on entangled photons are essential for solving questions in fundamental physics and are at the heart of quantum information science1. Specifically, the realization of high-dimensional states (D-level quantum systems, that is, qudits, with D > 2) and their control are necessary for fundamental investigations of quantum mechanics2, for increasing the sensitivity of quantum imaging schemes3, for improving the robustness and key rate of quantum communication protocols4, for enabling a richer variety of quantum simulations5, and for achieving more efficient and error-tolerant quantum computation6. Integrated photonics has recently become a leading platform for the co…
Distortion of the virtual photon cloud due to a static electric field
1988
The structure of the virtual transverse-photon cloud surrounding a ground-state hydrogen atom is considered in the presence of a uniform static electric field, which is capable of polarizing the atom. It is shown that this virtual cloud is distorted with respect to the spherically symmetric shape which is obtained when no static electric field is present. The distortion is carried by new components of the cloud, arising from the contributions of magnetic-dipole and electric-quadrupole virtual photons. These new contributions are shown to possess an overall cylindrical symmetry around the direction of the static field, and to be present also at large distances from the atom. The possibility …