4,939 research outputs found
Hybrid Atom--Photon Quantum Gate in a Superconducting Microwave Resonator
We propose a novel hybrid quantum gate between an atom and a microwave photon
in a superconducting coplanar waveguide cavity by exploiting the strong
resonant microwave coupling between adjacent Rydberg states. Using
experimentally achievable parameters gate fidelities are possible on
sub-s timescales for waveguide temperatures below 40 mK. This provides a
mechanism for generating entanglement between two disparate quantum systems and
represents an important step in the creation of a hybrid quantum interface
applicable for both quantum simulation and quantum information processing.Comment: 4 pages, 4 figure
Estimation of the geophysical properties of the ocean surface using aircraft microwave measurements
An improved model of the effects of sea state on microwave signature has been developed which incorporates the different effects of whitecaps and streaks to define the response of microwave channels to wind speed. This model has been demonstrated to agree with recent measurements. An approximation model has also been incorporated to describe the effects of precipitation on microwave radiation through a computationally rapid routine. The use of these models and a new technique to allow the selection of the most climatologically appropriate D-matrix is demonstrated in the inversion of data collected over the bering Sea. Surface wind speed agrees very well with observations while good results are obtained for integrated water vapor, and liquid water
Optimized Coplanar Waveguide Resonators for a Superconductor-Atom Interface
We describe the design and characterization of superconducting coplanar
waveguide cavities tailored to facilitate strong coupling between
superconducting quantum circuits and single trapped Rydberg atoms. For initial
superconductor-atom experiments at 4.2 K, we show that resonator quality
factors above can be readily achieved. Furthermore, we demonstrate that
the incorporation of thick-film copper electrodes at a voltage antinode of the
resonator provides a route to enhance the zero-point electric fields of the
resonator in a trapping region that is 40 m above the chip surface,
thereby minimizing chip heating from scattered trap light. The combination of
high resonator quality factor and strong electric dipole coupling between the
resonator and the atom should make it possible to achieve the strong coupling
limit of cavity quantum electrodynamics with this system.Comment: 4 pages, 4 figure
Multi-stakeholder process of co-designing small-scale fisheries policy in South Africa.
In 2005, a group of researchers, community-based organizations and lawyers got together with small-scale fishers to launch a class action law suit against the government of South Africa in its allocation system of Individual Transferable Quotas, on the ground that the system was unfair to small-scale fishing communities and threatened their right to practise their livelihoods. This effort resulted in the cabinet adoption of a new small-scale fisheries policy in 2014, with amendments being made to fisheries law (the Marine Living Resource Act 18 of 1998) to accommodate the issues and concerns of small-scale fisheries. Draft regulations and an implementation plan have recently been released, paving the way for the implementation of small-scale fisheries allocations in 2016. These legal and policy shifts are of great significance for small-scale fisheries, both in South Africa and elsewhere, and deserve careful examination. This paper discusses the processes leading to the development of a new small-scale fisheries policy and what has followed since. Specifically, the analysis focuses on a variety of collaborations between scholars from different disciplines; researchers from multiple fields; community practitioners representing diverse professional and community perspectives; and community organizations across local, state, national and international levels. The paper uses a model of change that crosses research and practitioner boundaries based on three key strategies: getting noticed; organizing at scale; and getting a seat at the negotiation table. It also considers the “transdisciplinary” process of involving all relevant actors in strategic, collective, reflection–action–reflection–action “from below”, which was crucial in the co-designing of this small-scale policy formulation in South Africa
Antiferromagnetic Domain Wall Engineering in Chromium Films
We have engineered an antiferromagnetic domain wall by utilizing a magnetic
frustration effect of a thin iron cap layer deposited on a chromium film.
Through lithography and wet etching we selectively remove areas of the Fe cap
layer to form a patterned ferromagnetic mask over the Cr film. Removing the Fe
locally removes magnetic frustration in user-defined regions of the Cr film. We
present x-ray microdiffraction microscopy results confirming the formation of a
90{\deg} spin-density wave propagation domain wall in Cr. This domain wall
nucleates at the boundary defined by our Fe mask.Comment: submitted to AP
MeerKAT HI line observations of the nearby interacting galaxy pair NGC 1512/1510
We present MeerKAT HI line observations of the nearby interacting galaxy pair
NGC 1512/1510. The MeerKAT data yield high-fidelity image sets characterised by
an excellent combination of high angular resolution (~20") and and sensitivity
(~0.08 Msun/pc^2), thereby offering the most detailed view of this well-studied
system's neutral atomic hydrogen content, especially the HI co-located with the
optical components of the galaxies. The stellar bulge and bar of NGC 1512 are
located within a central HI depression where surface densities fall below 1
Msun/pc^2, while the galaxy's starburst ring coincides with a well-defined HI
annulus delimited by a surface density of 3 Msun/pc^2. In stark contrast, the
star-bursting companion, NGC 1510, has its young stellar population precisely
matched to the highest HI over-densities we measure (~12.5 Msun/pc^2). The
improved quality of the MeerKAT data warrants the first detailed measurements
of the lengths and masses of the system's tidally-induced HI arms. We measure
the longest of the two prominent HI arms to extend over ~27 kpc and to contain
more than 30% of the system's total HI mass. We quantitatively explore the
spatial correlation between HI and far-ultraviolet flux over a large range of
HI mass surface densities spanning the outer disk. The results indicate the
system's HI content to play an important role in setting the pre-conditions
required for wide-spread, high-mass star formation. This work serves as a
demonstration of the remarkable efficiency and accuracy with which MeerKAT can
image nearby systems in HI line emission.Comment: 12 pages, 11 figures. Submitted only to arXi
Reducing Rydberg state dc polarizability by microwave dressing
We demonstrate reduction of the dc polarizability of Cesium atom Rydberg
states in a 77 K environment utilizing microwave field dressing. In particular
we reduce the polarizability of states which have resonances at
5.35 GHz to , suitable for interfacing Rydberg atoms to
superconducting resonators in a cryogenic environment. We measure the
polarizability of the Rydberg states using Magneto-Optical-Trap (MOT) loss
spectroscopy. Using an off-resonant radio-frequency (RF) dressing field
coupling and we demonstrate a reduction in dc
polarizability of the states over 80. Experimental findings
are in good agreement with a numerical model of the atom-dressing field system
developed using the Shirley-Floquet formalism. We also demonstrate that the dc
polarizability reduction is highly anisotropic, with near total nulling
possible when the dc and dressing fields are aligned, but only a factor of two
reduction in polarizability when the fields are orthogonal. These results may
aid in stabilizing Rydberg resonances against varying dc fields present near
surfaces, enabling advancement in the development of hybrid Rydberg atom -
superconducting resonator quantum gates
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