Generation of entangled states of two three-level atoms in cavity QED

We present a scheme to generate maximally entangled states of two three-level atoms with a nonresonant cavity by cavity-assisted collisions. Since the cavity field is only virtually excited no quantum information will be transferred from the atoms to the cavity.Comment: accepted for publication in PR

High-frequency gate manipulation of a bilayer graphene quantum dot

We report transport data obtained for a double-gated bilayer graphene quantum dot. In Coulomb blockade measurements, the gate dielectric Cytop(TM) is found to provide remarkable electronic stability even at cryogenic temperatures. Moreover, we demonstrate gate manipulation with square shaped voltage pulses at frequencies up to 100 MHz and show that the signal amplitude is not affected by the presence of the capacitively coupled back gate

Oxygen in dense interstellar gas - the oxygen abundance of the star forming core rho Oph A

Oxygen is the third most abundant element in the universe, but its chemistry in the interstellar medium is still not well understood. In order to critically examine the entire oxygen budget, we attempt here initially to estimate the abundance of atomic oxygen, O, in the only one region, where molecular oxygen, O2, has been detected to date. We analyse ISOCAM-CVF spectral image data toward rho Oph A to derive the temperatures and column densities of H2 at the locations of ISO-LWS observations of two [OI] 3P_J lines. The intensity ratios of the (J=1-2) 63um to (J=0-1) 145um lines largely exceed ten, attesting to the fact that these lines are optically thin. This is confirmed by radiative transfer calculations, making these lines suitable for abundance determinations. For that purpose, we calculate line strengths and compare them to the LWS observations. Excess [OI] emission is observed to be associated with the molecular outflow from VLA 1623. For this region, we determine the physical parameters, T and N(H2), from the CAM observations and the gas density, n(H2), is determined from the flux ratio of the [O I]63um and [O I]145um lines. For the oxygen abundance, our analysis leads to essentially three possibilities: (1) Extended low density gas with standard ISM O-abundance, (2) Compact high density gas with standard ISM O-abundance and (3) Extended high density gas with reduced oxygen abundance, [O/H] ~ 2E-5. As option (1) disregards valid [O I] 145um data, we do not find it very compelling; we favour option (3), as lower abundances are expected as a result of chemical cloud evolution, but we are not able to dismiss option (2) entirely. Observations at higher angular resolution than offered by the LWS are required to decide between these possibilities.Comment: Accepted for publication in A&