Lie algebra and invariant tensor technology for g2

Proceeding in analogy with su(n) work on lambda matrices and f- and d-tensors, this paper develops the technology of the Lie algebra g2, its seven dimensional defining representation gamma and the full set of invariant tensors that arise in relation thereto. A comprehensive listing of identities involving these tensors is given. This includes identities that depend on use of characteristic equations, especially for gamma, and a good body of results involving the quadratic, sextic and (the non-primitivity of) other Casimir operators of g2.Comment: 29 pages, LaTe

Scalable solid-state quantum processor using subradiant two-atom states

We propose a realization of a scalable, high-performance quantum processor whose qubits are represented by the ground and subradiant states of effective dimers formed by pairs of two-level systems coupled by resonant dipole-dipole interaction. The dimers are implanted in low-temperature solid host material at controllable nanoscale separations. The two-qubit entanglement either relies on the coherent excitation exchange between the dimers or is mediated by external laser fields.Comment: 4 pages, 3 figure

NMR evidence for Friedel-like oscillations in the CuO chains of ortho-II YBa2_2Cu3_3O6.5_{6.5}

Nuclear magnetic resonance (NMR) measurements of CuO chains of detwinned Ortho-II YBa$_2$Cu$_3$O$_{6.5}$ (YBCO6.5) single crystals reveal unusual and remarkable properties. The chain Cu resonance broadens significantly, but gradually, on cooling from room temperature. The lineshape and its temperature dependence are substantially different from that of a conventional spin/charge density wave (S/CDW) phase transition. Instead, the line broadening is attributed to small amplitude static spin and charge density oscillations with spatially varying amplitudes connected with the ends of the finite length chains. The influence of this CuO chain phenomenon is also clearly manifested in the plane Cu NMR.Comment: 4 pages, 3 figures, refereed articl

Photon-added coherent states as nonlinear coherent states

The states $|\alpha,m>$, defined as ${a^{\dagger}}^{m}|\alpha>$ up to a normalization constant and $m$ is a nonnegative integer, are shown to be the eigenstates of $f(\hat{n},m)\hat{a}$ where $f(\hat{n},m)$ is a nonlinear function of the number operator $\hat{n}$. The explicit form of $f(\hat{n},m)$ is constructed. The eigenstates of this operator for negative values of $m$ are introduced. The properties of these states are discussed and compared with those of the state $|\alpha,m >$.Comment: Rev Tex file with two figures as postscript files attached. Email: [email protected]

Real Forms of the Oscillator Quantum Algebra and its Representations

We consider the conditions under which the $q$-oscillator algebra becomes a Hopf $*$-algebra. In particular, we show that there are at least two real forms associated with the algebra. Furthermore, through the representations, it is shown that they are related to ${\text {su}}_{q^{1/2}}(2)$ with different conjugations.Comment: 10 pages, Ams-Tex, To be published in Letters in Mathematical physic

Hyperfine Fields in an Ag/Fe Multilayer Film Investigated with 8Li beta-Detected Nuclear Magnetic Resonance

Low energy $\beta$-detected nuclear magnetic resonance ($\beta$-NMR) was used to investigate the spatial dependence of the hyperfine magnetic fields induced by Fe in the nonmagnetic Ag of an Au(40 \AA)/Ag(200 \AA)/Fe(140 \AA) (001) magnetic multilayer (MML) grown on GaAs. The resonance lineshape in the Ag layer shows dramatic broadening compared to intrinsic Ag. This broadening is attributed to large induced magnetic fields in this layer by the magnetic Fe layer. We find that the induced hyperfine field in the Ag follows a power law decay away from the Ag/Fe interface with power $-1.93(8)$, and a field extrapolated to $0.23(5)$ T at the interface.Comment: 5 pages, 4 figure. To be published in Phys. Rev.