60,046 research outputs found
Positronium ions and molecules
Recent theoretical studies on positronium ions and molecules are discussed. A positronium ion is a three particle system consisting of two electrons in singlet spin state, and a positron. Recent studies include calculations of its binding energy, positron annihilation rate, and investigations of its doubly excited resonant states. A positronium molecule is a four body system consisting of two positrons and two electrons in an overall singlet spin state. The recent calculations of its binding energy against the dissociation into two positronium atoms, and studies of auto-detaching states in positronium molecules are discussed. These auto-dissociating states, which are believed to be part of the Rydberg series as a result of a positron attaching to a negatively charged positronium ion, Ps-, would appear as resonances in Ps-Ps scattering
Minority Game With Peer Pressure
To study the interplay between global market choice and local peer pressure,
we construct a minority-game-like econophysical model. In this so-called
networked minority game model, every selfish player uses both the historical
minority choice of the population and the historical choice of one's neighbors
in an unbiased manner to make decision. Results of numerical simulation show
that the level of cooperation in the networked minority game differs remarkably
from the original minority game as well as the prediction of the
crowd-anticrowd theory. We argue that the deviation from the crowd-anticrowd
theory is due to the negligence of the effect of a four point correlation
function in the effective Hamiltonian of the system.Comment: 10 pages, 3 figures in revtex 4.
Dynamics of thermalisation in small Hubbard-model systems
We study numerically the thermalisation and temporal evolution of the reduced
density matrix for a two-site subsystem of a fermionic Hubbard model prepared
far from equilibrium at a definite energy. Even for very small systems near
quantum degeneracy, the subsystem can reach a steady state resembling
equilibrium. This occurs for a non-perturbative coupling between the subsystem
and the rest of the lattice where relaxation to equilibrium is Gaussian in
time, in sharp contrast to perturbative results. We find similar results for
random couplings, suggesting such behaviour is generic for small systems.Comment: 4 pages, 5 figure
Feshbach resonant scattering of three fermions in one-dimensional wells
We study the weak-tunnelling limit for a system of cold 40K atoms trapped in
a one-dimensional optical lattice close to an s-wave Feshbach resonance. We
calculate the local spectrum for three atoms at one site of the lattice within
a two-channel model. Our results indicate that, for this one-dimensional
system, one- and two-channel models will differ close to the Feshbach
resonance, although the two theories would converge in the limit of strong
Feshbach coupling. We also find level crossings in the low-energy spectrum of a
single well with three atoms that may lead to quantum phase transition for an
optical lattice of many wells. We discuss the stability of the system to a
phase with non-uniform density.Comment: 10 pages, 5 figure
On pattern classification algorithms - Introduction and survey
Pattern recognition algorithms, and mathematical techniques of estimation, decision making, and optimization theor
An Adaptive Entanglement Distillation Scheme Using Quantum Low Density Parity Check Codes
Quantum low density parity check (QLDPC) codes are useful primitives for
quantum information processing because they can be encoded and decoded
efficiently. Besides, the error correcting capability of a few QLDPC codes
exceeds the quantum Gilbert-Varshamov bound. Here, we report a numerical
performance analysis of an adaptive entanglement distillation scheme using
QLDPC codes. In particular, we find that the expected yield of our adaptive
distillation scheme to combat depolarization errors exceed that of Leung and
Shor whenever the error probability is less than about 0.07 or greater than
about 0.28. This finding illustrates the effectiveness of using QLDPC codes in
entanglement distillation.Comment: 12 pages, 6 figure
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