Protecting the SWAP\sqrt{SWAP} operation from general and residual errors by continuous dynamical decoupling

We study the occurrence of errors in a continuously decoupled two-qubit state during a $\sqrt{SWAP}$ quantum operation under decoherence. We consider a realization of this quantum gate based on the Heisenberg exchange interaction, which alone suffices for achieving universal quantum computation. Furthermore, we introduce a continuous-dynamical-decoupling scheme that commutes with the Heisenberg Hamiltonian to protect it from the amplitude damping and dephasing errors caused by the system-environment interaction. We consider two error-protection settings. One protects the qubits from both amplitude damping and dephasing errors. The other features the amplitude damping as a residual error and protects the qubits from dephasing errors only. In both settings, we investigate the interaction of qubits with common and independent environments separately. We study how errors affect the entanglement and fidelity for different environmental spectral densities.Comment: Extended version of arXiv:1005.1666. To appear in PR

A study on the multicolour evolution of Red Sequence galaxy populations: insights from hydrodynamical simulations and semi-analytical models

By means of our own cosmological-hydrodynamical simulation and semi-analytical model we studied galaxy population properties in clusters and groups, spanning over 10 different bands from UV to NIR, and their evolution since redshift z=2. We compare our results in terms of galaxy red/blue fractions and luminous-to-faint ratio (LFR) on the Red Sequence (RS) with recent observational data reaching beyond z=1.5. Different selection criteria were tested in order to retrieve galaxies belonging to the RS: either by their quiescence degree measured from their specific SFR ("Dead Sequence"), or by their position in a colour-colour plane which is also a function of sSFR. In both cases, the colour cut and the limiting magnitude threshold were let evolving with redshift, in order to follow the natural shift of the characteristic luminosity in the LF. We find that the Butcher-Oemler effect is wavelength-dependent, with the fraction of blue galaxies increasing steeper in optical colours than in NIR. Besides, only when applying a lower limit in terms of fixed absolute magnitude, a steep BO effect can be reproduced, while the blue fraction results less evolving when selecting samples by stellar mass or an evolving magnitude limit. We then find that also the RS-LFR behaviour, highly debated in the literature, is strongly dependent on the galaxy selection function: in particular its very mild evolution recovered when measured in terms of stellar mass, is in agreement with values reported for some of the highest redshift confirmed (proto)clusters. As to differences through environments, we find that normal groups and (to a lesser extent) cluster outskirts present the highest values of both star forming fraction and LFR at low z, while fossil groups and cluster cores the lowest: this separation among groups begins after z~0.5, while earlier all group star forming properties are undistinguishable.Comment: revised version, A&A accepted (11 pages, 6 figures

Evolution of the Mass-Metallicity relations in passive and star-forming galaxies from SPH-cosmological simulations

We present results from SPH-cosmological simulations, including self-consistent modelling of SN feedback and chemical evolution, of galaxies belonging to two clusters and twelve groups. We reproduce the mass-metallicity (ZM) relation of galaxies classified in two samples according to their star-forming activity, as parametrized by their sSFR, across a redshift range up to z=2. Its slope shows irrelevant evolution in the passive sample, being steeper in groups than in clusters. However, the sub-sample of high-mass passive galaxies only is characterized by a steep increase of the slope with redshift, from which it can be inferred that the bulk of the slope evolution of the ZM relation is driven by the more massive passive objects. (...ABRIDGED...) The ZM relation for the star-forming sample reveals an increasing scatter with redshift, indicating that it is still being built at early epochs. The star-forming galaxies make up a tight sequence in the SFR-M_* plane at high redshift, whose scatter increases with time alongside with the consolidation of the passive sequence. We also confirm the anti-correlation between sSFR and stellar mass, pointing at a key role of the former in determining the galaxy downsizing, as the most significant means of diagnostics of the star formation efficiency. Likewise, an anti-correlation between sSFR and metallicity can be established for the star-forming galaxies, while on the contrary more active galaxies in terms of simple SFR are also metal-richer. We discuss these results in terms of the mechanisms driving the evolution within the high- and low-mass regimes at different epochs: mergers, feedback-driven outflows and the intrinsic variation of the star formation efficiency.Comment: Emended list of author

Second trimester abnormal uterine artery Dopplers and adverse obstetric and neonatal outcomes when PAPP-a is normal

OBJECTIVES: To explore the association between abnormal uterine artery Dopplers (combined PI > 2.5) - with normal PAPP-A - and adverse obstetric/neonatal outcomes. METHODS: This was a retrospective cohort study of 800 patients between 1 March 2019 - 23 November 2021 in a tertiary UK hospital, where it is routine to measure uterine artery Dopplers of all pregnancies during their anomaly scans. 400 nulliparous women/birthing people with complete data were included. 400 nulliparous controls scanned in the same time frame (1.5 years) with normal PAPP-A and uterine artery Dopplers were matched for age and BMI. Outcomes included: mode of birth, postpartum complications, birth weight/centile, Apgar score, gestational age at delivery, neonatal unit admission, and clinical neonatal hypoglycemia. Multivariable analysis was used. RESULTS: Compared to controls, pregnancies with abnormal uterine artery Dopplers and normal PAPP-A were at increased risk of induction (46.5% vs 35.5%, p = .042), cesarean section (46.0% vs 38.0%, p = .002), emergency cesarean section (35.0% vs 26.5%, p = .009), and pre-eclampsia 5.8% vs 2.5%, p = .021). Their babies were more likely to be admitted to the neonatal unit - mostly for prematurity (15.3% vs 6.3%, p = .0004), hypoglycemia (4.0% vs 1.0%, p = .007), be small for gestational age (26.5% vs 11.5%, p = .0001), had intrauterine growth restriction (10.8% vs 1.3%, p = .0001), and be born prematurely (10.0% vs 3.5%, p = .002). Routine measurement of uterine artery Dopplers increased the detection rate of small for gestational age fetuses by 15.1%. Over half of the babies admitted with neonatal hypoglycemia in pregnancies with abnormal uterine artery Dopplers had an unexplained cause. CONCLUSIONS: Pregnancies with abnormal uterine Dopplers are not only at increased risk of pre-eclampsia and small for gestational age fetuses/intrauterine growth restriction, but are also at increased risk of emergency cesarean section and adverse neonatal outcomes. The increased incidence of neonatal hypoglycemia is likely driven to some degree by prematurity and placental complications, but possibly also by undiagnosed glucose dysmetabolism. This may warrant routine measurement of uterine artery Dopplers in all pregnancies (regardless of risk), where feasible, to aid antenatal management and counseling

Non-Newtonian gravity in finite nuclei

In this talk, we report our recent study of constraining the non-Newtonian gravity at femtometer scale. We incorporate the Yukawa-type non-Newtonian gravitational potential consistently to the Skyrme functional form using the exact treatment for the direct contribution and density-matrix expansion method for the exchange contribution. The effects from the non-Newtonian potential on finite nuclei properties are then studied together with a well-tested Skyrme force. Assuming that the framework without non-Newtonian gravity can explain the binding energies and charge radii of medium to heavy nuclei within 2% error, we set an upper limit for the strength of the non-Newtonian gravitational potential at femtometer scale.Comment: Talk given at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS

Protection of entanglement from sudden death using continuous dynamical decoupling

We show that continuous dynamical decoupling can protect a two-qubit entangled state from sudden death at finite temperature due to uncorrelated dephasing, bit flipping, and dissipation. We consider a situation where an entangled state shared between two non-interacting qubits is initially prepared and left evolve under the environmental perturbations and the protection of external fields. To illustrate the protection of the entanglement, we solve numerically a master equation in the Born approximation, considering independent boson fields at the same temperature coupled to the different error agents of each qubit

The first joint ESGAR/ ESPR consensus statement on the technical performance of cross-sectional small bowel and colonic imaging

Objectives: To develop guidelines describing a standardised approach to patient preparation and acquisition protocols for magnetic resonance imaging (MRI), computed tomography (CT) and ultrasound (US) of the small bowel and colon, with an emphasis on imaging inflammatory bowel disease. Methods: An expert consensus committee of 13 members from the European Society of Gastrointestinal and Abdominal Radiology (ESGAR) and European Society of Paediatric Radiology (ESPR) undertook a six-stage modified Delphi process, including a detailed literature review, to create a series of consensus statements concerning patient preparation, imaging hardware and image acquisition protocols. Results: One hundred and fifty-seven statements were scored for agreement by the panel of which 129 statements (82 %) achieved immediate consensus with a further 19 (12 %) achieving consensus after appropriate modification. Nine (6 %) statements were rejected as consensus could not be reached. Conclusions: These expert consensus recommendations can be used to help guide cross-sectional radiological practice for imaging the small bowel and colon. Key points: • Cross-sectional imaging is increasingly used to evaluate the bowel • Image quality is paramount to achieving high diagnostic accuracy • Guidelines concerning patient preparation and image acquisition protocols are provided