Optoelectronic integrated circuits incorporating twin ring diode lasers with InAs/InGaAs/GaAs quantum-dot active region have been fabricated and characterized. Directional control and unidirectional operation of ring diode lasers are demonstrated by forward biasing an S-section waveguide incorporated within the ring cavity. Mode-beating spectra from individual ring diode lasers are observed at ...

We determine the ring structure of the equivariant quantum cohomology of the Hilbert scheme of points of C2. The operator of quantum multiplication by the divisor class is a nonstationary deformation of the quantum Calogero-Sutherland many-body system. Several results and conjectures on the corresponding deformation of Jack symmetric functions are presented. A relationship between the quantum c...

in this paper, we introduce a class of $j$-quasipolar rings. let $r$ be a ring with identity. an element $a$ of a ring $r$ is called {it weakly $j$-quasipolar} if there exists $p^2 = pin comm^2(a)$ such that $a + p$ or $a-p$ are contained in $j(r)$ and the ring $r$ is called {it weakly $j$-quasipolar} if every element of $r$ is weakly $j$-quasipolar. we give many characterizations and investiga...

A large chunk of the intersection theory of the moduli stacks of n-marked, genus 0 stable maps to a specified target variety X is encoded by the quantum cohomology ring of X. In particular, one can use the associativity of the ring structure to calculate Gromov-Witten invariants and, thus, in favorable circumstances, to calculate the number of rational curves in X passing through an appropriate...

in this paper, we investigate various kinds of extensions of twin-good rings. moreover, we prove that every element of an abelian neat ring r is twin-good if and only if r has no factor ring isomorphic to z2  or z3. the main result of [24] states some conditions that any right self-injective ring r is twin-good. we extend this result to any regular baer ring r by proving that every element of a...

Recent experiments are reviewed that explore the spin states of a ring-shaped manyelectron quantum dot. Coulomb-blockade spectroscopy is used to access the spin degree of freedom. The Zeeman effect observed for states with successive electron number allows to select possible sequences of spin ground states of the ring. Spinpaired orbital levels can be identified by probing their response to mag...

The paper explores the basic geometrical properties of the observables characterizing two-qubit systems by employing a novel projective ring geometric approach. After introducing the basic facts about quantum complementarity and maximal quantum entanglement in such systems, we demonstrate that the 15×15 multiplication table of the associated four-dimensional matrices exhibits a so-far-unnoticed...