Spin-based quantum gating with semiconductor quantum dots by bichromatic radiation method

A potential scheme is proposed for realizing a two-qubit quantum gate in semiconductor quantum dots. Information is encoded in the spin degrees of freedom of one excess conduction electron of each quantum dot. We propose to use two lasers, radiation two neighboring QDs, and tuned to blue detuning with respect to the resonant frequencies of individual excitons. The two-qubit phase gate can be achieved by means of both Pauli-blocking effect and dipole-dipole coupling between intermediate excitonic states.Comment: Europhysics Letters 66 (2004) 1

Timing the Parkes Multibeam Pulsars

Measurement of accurate positions, pulse periods and period derivatives is an essential follow-up to any pulsar survey. The procedures being used to obtain timing parameters for the pulsars discovered in the Parkes multibeam pulsar survey are described. Completed solutions have been obtained so far for about 80 pulsars. They show that the survey is preferentially finding pulsars with higher than average surface dipole magnetic fields. Eight pulsars have been shown to be members of binary systems and some of the more interesting results relating to these are presented.Comment: 6 pages, 2 embedded EPS figures, to be published in proceedings of "Pulsar Astronomy - 2000 and Beyond", ASP Conf. Se

Timing the millisecond pulsars in 47 Tucanae

In the last 10 years 20 millisecond pulsars have been discovered in the globular cluster 47 Tucanae. Hitherto, only 3 of these had published timing solutions. Here we improve upon these 3 and present 12 new solutions. These measurements can be used to determine a variety of physical properties of the pulsars and of the cluster. The 15 pulsars have positions determined with typical uncertianties of only a few milliarcsec and they are all located within 1.2 arcmin of the cluster centre. We have also measured the proper motions of 5 of the pulsars, which are consistent with the proper motion of 47 Tuc based on Hipparcos data. The period derivatives measured for many of the pulsars are dominated by the dynamical effects of the cluster gravitational field, and are used to constrain the surface mass density of the cluster. All pulsars have characteristic ages T > 170 Myr and magnetic fields B < 2.4e9 Gauss, and the average T > 1 Gyr. We have measured the rate of advance of periastron for the binary pulsar J0024-7204H, implying a total system mass 1.4+-0.8 solar masses.Comment: 17 pages, 11 included figures, accepted for publication in MNRA

Cost-effectiveness of intravitreal therapy with both anti-VEGF and Dexamethasone implant in patients with Diabetic Macular Edema

Purpose: The aim of this study was to evaluate the cost-effectiveness of intravitreal therapy (IVT) with both anti-VEGF and Dexamethasone implant in patients with Diabetic Macular Edema (DME) during two years’ follow-up. Methods: A retrospective review of 191 patients (382 eyes) with type I and II diabetes and DME was performed. Pre-IVT and final best correct visual acuity (BCVA), central macular thickness (CMT), intraocular pressure (IOP), number and type of IVT,number of examinations, and fluorescein angiography were assessed. Based on surgery procedure other than IVT, patients were divided into 5 groups. To avoid bias, we analysed only patients who had undergone cataract surgery before (group 1) or during enrolment (group 2). Results: 41 eyes from Group 1 and 48 eyes from group 2 were evaluated. Median BCVA ranged between 20/80 and 20/63 Snellen (P = 0.008) in Group 1 and from 20/63 to 20/40 Snellen (P = 0.0035) in Group 2, while improvement up to 1 Snellen line was observed in 58.5 and 68.75% of eyes in Group 1 and 2, respectively.In terms of median CMT, a statistically reduction (P = 0.0007) was found in Group 2 (-85 μm), whereas no statistical differences were found in Group 1. The two groups showed no statistically significant difference in median IOP. The estimated cost per eye was €7803 in Group 1 and €8988 Group 2, whereas the mean cost per patient was €15190 and €16580 in Group 1 and 2, respectively. Analysis between groups did not show any statistical difference in the considered parameters. Conclusions: In this study, despite the high treatment cost, vision improvement in DME patients undergoing IVT was disappointing. Our results emphasise the need for a better understanding of the cost-effectiveness of DME treatmen

PSR J1723-2837: An Eclipsing Binary Radio Millisecond Pulsar

We present a study of PSR J1723-2837, an eclipsing, 1.86 ms millisecond binary radio pulsar discovered in the Parkes Multibeam survey. Radio timing indicates that the pulsar has a circular orbit with a 15 hr orbital period, a low-mass companion, and a measurable orbital period derivative. The eclipse fraction of ~15% during the pulsar's orbit is twice the Roche lobe size inferred for the companion. The timing behavior is significantly affected by unmodeled systematics of astrophysical origin, and higher-order orbital period derivatives are needed in the timing solution to account for these variations. We have identified the pulsar's (non-degenerate) companion using archival ultraviolet, optical, and infrared survey data and new optical photometry. Doppler shifts from optical spectroscopy confirm the star's association with the pulsar and indicate a pulsar-to-companion mass ratio of 3.3 +/- 0.5, corresponding to a companion mass range of 0.4 to 0.7 Msun and an orbital inclination angle range of between 30 and 41 degrees, assuming a pulsar mass range of 1.4-2.0 Msun. Spectroscopy indicates a spectral type of G for the companion and an inferred Roche-lobe-filling distance that is consistent with the distance estimated from radio dispersion. The features of PSR J1723-2837 indicate that it is likely a "redback" system. Unlike the five other Galactic redbacks discovered to date, PSR J1723-2837 has not been detected as a gamma-ray source with Fermi. This may be due to an intrinsic spin-down luminosity that is much smaller than the measured value if the unmeasured contribution from proper motion is large.Comment: 11 pages, including 8 figures and 5 tables. Accepted by the Astrophysical Journa