Robust phase-controlled gates for scalable atomic quantum processors using optical standing waves

A simple scheme is presented for realizing robust optically controlled quantum gates for scalable atomic quantum processors by driving the qubits with optical standing waves. Atoms localized close to the antinodes of the standing wave can realize phase-controlled quantum operations that are potentially more than an order of magnitude less sensitive to the local optical phase and atomic motion than corresponding travelling wave configurations. The scheme is compatible with robust optimal control techniques and spatial qubit addressing in atomic arrays to realize phase controlled operations without the need for tight focusing and precise positioning of the control lasers. This will be particularly beneficial for quantum gates involving Doppler sensitive optical frequency transitions and provides an all optical route to scaling up atomic quantum processors.Comment: Accepted in Quantu

Collective excitation of Rydberg-atom ensembles beyond the N\sqrt{N} enhancement

In an ensemble of laser-driven atoms involving strongly interacting Rydberg states, the excitation probability is usually strongly suppressed. In contrast, here we identify a regime in which the steady-state Rydberg excited fraction is enhanced by the interaction. This effect is associated with the build-up of many-body coherences, induced by coherent multi-photon excitations between collective states. The excitation enhancement should be observable under currently-existing experimental conditions, and may serve as a direct probe for the presence of coherent multi-photon dynamics involving collective quantum states.Comment: 7 pages, 4 figure

Sub-Poissonian statistics of Rydberg-interacting dark-state polaritons

Interfacing light and matter at the quantum level is at the heart of modern atomic and optical physics and enables new quantum technologies involving the manipulation of single photons and atoms. A prototypical atom-light interface is electromagnetically induced transparency, in which quantum interference gives rise to hybrid states of photons and atoms called dark-state polaritons. We have observed individual dark-state polaritons as they propagate through an ultracold atomic gas involving Rydberg states. Strong long-range interactions between Rydberg atoms give rise to an effective interaction blockade for dark-state polaritons, which results in large optical nonlinearities and modified polariton number statistics. The observed statistical fluctuations drop well below the quantum noise limit indicating that photon correlations modified by the strong interactions have a significant back-action on the Rydberg atom statistics.Comment: 7 pages, 4 figure

Two-dimensional spectroscopy of Rydberg gases

Two-dimensional (2D) spectroscopy uses multiple electromagnetic pulses to infer the properties of a complex system. A paradigmatic class of target systems are molecular aggregates, for which one can obtain information on the eigenstates, various types of static and dynamic disorder and on relaxation processes. However, two-dimensional spectra can be difficult to interpret without precise knowledge of how the signal components relate to microscopic Hamiltonian parameters and system-bath interactions. Here we show that two-dimensional spectroscopy can be mapped in the microwave domain to highly controllable Rydberg quantum simulators. By porting 2D spectroscopy to Rydberg atoms, we firstly open the possibility of its experimental quantum simulation, in a case where parameters and interactions are very well known. Secondly, the technique may provide additional handles for experimental access to coherences between system states and the ability to discriminate different types of decoherence mechanisms in Rydberg gases. We investigate the requirements for a specific implementation utilizing multiple phase coherent microwave pulses and a phase cycling technique to isolate signal components.Comment: 34 pages, 9 figure

Radiofrequency spectroscopy of a linear array of Bose-Einstein condensates in a magnetic lattice

We report site-resolved radiofrequency spectroscopy measurements of Bose-Einstein condensates of 87Rb atoms in about 100 sites of a one-dimensional 10 micron-period magnetic lattice produced by a grooved magnetic film plus bias fields. Site-to-site variations of the trap bottom, atom temperature, condensate fraction and chemical potential indicate that the magnetic lattice is remarkably uniform, with variations in trap bottoms of only +/- 0.4 mG. At the lowest trap frequencies (radial and axial frequencies 1.5 kHz and 260 Hz, respectively), temperatures down to 0.16 microkelvin are achieved in the magnetic lattice and at the smallest trap depths (50 kHz) condensate fractions up to 80% are observed. With increasing radial trap frequency (up to 20 kHz, or aspect ratio up to about 80) large condensate fractions persist and the highly elongated clouds approach the quasi-1D Bose gas regime. The temperature estimated from analysis of the spectra is found to increase by a factor of about five which may be due to suppression of rethermalising collisions in the quasi-1D Bose gas. Measurements for different holding times in the lattice indicate a decay of the atom number with a half-life of about 0.9 s due to three-body losses and the appearance of a high temperature (about 1.5 microkelvin) component which is attributed to atoms that have acquired energy through collisions with energetic three-body decay products

UBRI Photometry of Globular Clusters in the Leo Group Galaxy NGC 3379

We present wide area UBRI photometry for globular clusters around the Leo group galaxy NGC 3379. Globular cluster candidates are selected from their B-band magnitudes and their (U-B)o vs (B-I)o colours. A colour-colour selection region was defined from photometry of the Milky Way and M31 globular cluster systems. We detect 133 globular cluster candidates which, supports previous claims of a low specific frequency for NGC 3379. The Milky Way and M31 reveal blue and red subpopulations, with (U-B)o and (B-I)o colours indicating mean metallicities similar to those expected based on previous spectroscopic work. The stellar population models of Maraston (2003) and Brocato etal (2000) are consistent with both subpopulations being old, and with metallicities of [Fe/H] \~ -1.5 and -0.6 for the blue and red subpopulations respectively. The models of Worthey (1994) do not reproduce the (U-B)o colours of the red (metal-rich) subpopulation for any modelled age. For NGC 3379 we detect a blue subpopulation with similar colours and presumably age/metallicity, to that of the Milky Way and M31 globular cluster systems. The red subpopulation is less well defined, perhaps due to increased photometric errors, but indicates a mean metallicity of [Fe/H] ~ -0.6.Comment: 12 pages, Latex, 10 figures, 1 table, submitted for publication in MNRAS, Fig. 11 available in source file or from [email protected]

Magnetic Lattices for Ultracold Atoms

This article reviews the development in our laboratory of magnetic lattices comprising periodic arrays of magnetic microtraps created by patterned magnetic films to trap periodic arrays of ultracold atoms. Recent achievements include the realisation of multiple Bose-Einstein condensates in a 10 $\mu$m-period one-dimensional magnetic lattice; the fabrication of sub-micron-period square and triangular magnetic lattice structures suitable for quantum tunnelling experiments; the trapping of ultracold atoms in a sub-micron-period triangular magnetic lattice; and a proposal to use long-range interacting Rydberg atoms to achieve spin-spin interactions between sites in a large-spacing magnetic lattice

Control of western corn rootworm via RNAi traits in maize: Lethal and sublethal effects of Sec23 dsRNA

Background: RNA interference (RNAi) triggered by maize plants expressing RNA hairpins against specific western corn rootworm ( WCR) transcripts have proven to be effective at controlling this pest. To provide robust crop protection, mRNA transcripts targeted by double-stranded RNA must be sensitive to knockdown and encode essential proteins. Results: Using WCR adult feeding assays, we identified Sec23 as a highly lethal RNAi target. Sec23 encodes a coatomer protein, a component of the coat protein (COPII) complex that mediates ER-Golgi transport. The lethality detected in WCR adults was also observed in early instar larvae, the life stage causing most of the crop damage, suggesting that WCR adults can serve as an alternative to larvae for dsRNA screening. Surprisingly, over 85% transcript inhibition resulted in less than 40% protein knockdown, suggesting that complete protein knockdown is not necessary for Sec23 RNAi-mediated mortality. The efficacy of Sec23 dsRNA for rootworm control was confirmed in planta; T0maize events carrying rootwormSec23 hairpin transgenes showed high levels of root protection in greenhouse assays. A reduction in larval survival and weight were observed in the offspring of WCR females exposed to Sec23 dsRNA LC25in diet bioassays. Conclusion: We describe Sec23 as RNAi target for in planta rootworm control. High mortality in exposed adult and larvae and moderate sublethal effects in the offspring of females exposed to Sec23 dsRNA LC25, suggest the potential for field application of this RNAi trait and the need to factor in responses to sublethal exposure into insect resistance management programs. Includes supplemental materials

RNAi targeting of rootworm \u3ci\u3eTroponin I\u3c/i\u3e transcripts confers root protection in maize

Western corn rootworm, Diabrotica virgifera virgifera, is the major agronomically important pest of maize in the US Corn Belt. To augment the repertoire of the available dsRNA-based traits that control rootworm, we explored a potentially haplolethal gene target, wings up A (wupA), which encodes Troponin I. Troponin I, a component of the Troponin-Tropomyosin complex, is an inhibitory protein involved in muscle contraction. In situ hybridization showed that feeding on wupA-targeted dsRNAs caused systemic transcript knockdown in D. v. virgifera larvae. The knockdown of wupA transcript, and by extension Troponin I protein, led to deterioration of the striated banding pattern in larval body muscle and decreased muscle integrity. Additionally, the loss of function of the circular muscles surrounding the alimentary system led to significant accumulation of food material in the hind gut, which is consistent with a loss of peristaltic motion of the alimentary canal. In this study, we demonstrate that wupA dsRNA is lethal in D. v. virgifera larvae when fed via artificial diet, with growth inhibition of up to 50% within two days of application. Further, wupA hairpins can be stably expressed and detected in maize. Maize expressing wupA hairpins exhibit robust root protection in greenhouse bioassays, with several maize transgene integration events showing root protection equivalent to commercial insecticidal protein-expressing maize