319 research outputs found
Single Atom Imaging with an sCMOS camera
Single atom imaging requires discrimination of weak photon count events above
background and has typically been performed using either EMCCD cameras,
photomultiplier tubes or single photon counting modules. sCMOS provides a cost
effective and highly scalable alternative to other single atom imaging
technologies, offering fast readout and larger sensor dimensions. We
demonstrate single atom resolved imaging of two site-addressable single atom
traps separated by 10~m using an sCMOS camera, offering a competitive
signal-to-noise ratio at intermediate count rates to allow high fidelity
readout discrimination (error ) and sub-m spatial resolution for
applications in quantum technologies.Comment: 4 pages, 4 figure
Trichloroethylene Extracted Soybean Oil Meal Poisoning
Studies conducted at Iowa State College during the past 10 months show that a fatal disease can be produced in cattle when fed certain batches of commercially prepared trichloroethylene-extracted soybean meal
Coherent control of addressable Rydberg atoms for hybrid quantum information processing
Neutral atoms provide an excellent resource for quantum information processing, combining the long atomic coherence times of the hyperfine ground-state with strong dipole-dipole interactions of highly excited Rydberg states for generating deterministic entanglement between qubits separated by < 10 µm [1]. Scalable long-range interactions can be obtained by coupling the atomic array to a superconducting microwave cavity enabling hybrid quantum information processing where the cavity-mediated entanglement allows atoms to be coupled over cm length scales. We present the first steps towards such an experiment incorporating high fidelity readout using an sCMOS camera [2] and the ability to drive fast, optically addressable rotations of the hyperfine-encoded qubits to the Rydberg state. Using our sub-kHz cavitystabilised laser system [3] we demonstrate coherent control of single Rydberg atoms, performing Ramsey spectroscopy to determine coherence time and to generate entanglement between a pair of atoms separated by 6 µm. Combining this excitation scheme with our ground-state Raman lasers we show progress towards the implementation of a mesoscopic Rydberg gate based on electromagnetically induced transparency (EIT) offering robust entanglement of multi-atom ensembles [4]
Entanglement of neutral-atom qubits with long ground-Rydberg coherence times
We report results of a ground-state entanglement protocol for a pair of Cs atoms separated by 6~μm, combining the Rydberg blockade mechanism with a two-photon Raman transitions to prepare the |Ψ+⟩=(|10⟩+|01⟩)/2‾√ Bell state with a loss-corrected fidelity of 0.81(5), equal to the best demonstrated fidelity for atoms trapped in optical tweezers but without the requirement for dynamically adjustable interatomic spacing. Qubit state coherence is also critical for quantum information applications, and we characterise both ground-state and ground-Rydberg dephasing rates using Ramsey spectroscopy. We demonstrate transverse dephasing times T∗2=10(1)~ms and T′2=0.14(1)~s for the qubit levels and achieve long ground-Rydberg coherence times of T∗2=17(2) μs as required for implementing high-fidelity multi-qubit gate sequences where a control atom remains in the Rydberg state while applying local operations on neighbouring target qubits
Quantum geometry from 2+1 AdS quantum gravity on the torus
Wilson observables for 2+1 quantum gravity with negative cosmological
constant, when the spatial manifold is a torus, exhibit several novel features:
signed area phases relate the observables assigned to homotopic loops, and
their commutators describe loop intersections, with properties that are not yet
fully understood. We describe progress in our study of this bracket, which can
be interpreted as a q-deformed Goldman bracket, and provide a geometrical
interpretation in terms of a quantum version of Pick's formula for the area of
a polygon with integer vertices.Comment: 19 pages, 11 figures, revised with more explanations, improved
figures and extra figures. To appear GER
Non-abelian gauge antisymmetric tensor fields
We construct the theory of non-abelian gauge antisymmetric tensor fields,
which generalize the standard Yang-MIlls fields and abelian gauge p-forms. The
corresponding gauge group acts on the space of inhomogeneous differential forms
and it is shown to be a supergroup. The wide class of generalized Chern-Simons
actions is constructed.Comment: 20 pages, Late
Abelian gerbes as a gauge theory of quantum mechanics on phase space
We construct a U(1) gerbe with a connection over a finite-dimensional,
classical phase space P. The connection is given by a triple of forms A,B,H: a
potential 1-form A, a Neveu-Schwarz potential 2-form B, and a field-strength
3-form H=dB. All three of them are defined exclusively in terms of elements
already present in P, the only external input being Planck's constant h. U(1)
gauge transformations acting on the triple A,B,H are also defined, parametrised
either by a 0-form or by a 1-form. While H remains gauge invariant in all
cases, quantumness vs. classicality appears as a choice of 0-form gauge for the
1-form A. The fact that [H]/2i\pi is an integral class in de Rham cohomology is
related with the discretisation of symplectic area on P. This is an equivalent,
coordinate-free reexpression of Heisenberg's uncertainty principle. A choice of
1-form gauge for the 2-form B relates our construction with generalised complex
structures on classical phase space. Altogether this allows one to interpret
the quantum mechanics corresponding to P as an Abelian gauge theory.Comment: 18 pages, 1 figure available from the authors upon reques
Extreme low flow effects on riverine fauna: a perspective on methodological assessments
River flow regimes face increasing pressure from human activities including water resource management operations and climate change. Consequently, extreme hydrological events are becoming more severe and commonplace, and there is a pressing need to understand and manage their ecological effects. Extreme low-flows (ELFs) – those displaying significantly greater magnitudes and durations than typical low-flow conditions – are being increasingly experienced globally. Fish and macroinvertebrate responses to ELFs have been more widely researched relative to other organism groups in riverine environments, although such studies have employed variable methodological techniques. In this perspective piece, we identify field-based assessments and controlled experiments as two key research paradigms used to examine riverine faunal responses to ELFs. Field-based assessments are often explorative and can benefit from utilising large-scale and long-term datasets. Alternatively, controlled experiments typically employ more hypothesis-driven approaches and can establish strong cause and effect linkages through high replication and control over potentially confounding parameters. Each paradigm clearly possesses their respective strengths, which we highlight and discuss how these could be better harnessed to optimise scientific advancements. To date, studies examining faunal responses to ELFs in these two research paradigms have largely been undertaken in parallel. Here, we argue that future research should seek to develop closer synergies to optimise the quality and quantity of evidence to better understand riverine faunal responses to ELFs. Such scientific advances are of paramount importance given the vulnerability of riverine fauna, and the ecosystems they comprise, as they face a new era of ELFs in many global regions
Non-holomorphic terms in N=2 SUSY Wilsonian actions and RG equation
In this paper we first investigate the Ansatz of one of the present authors
for K(\Psi,\bar\Psi), the adimensional modular invariant non-holomorphic
correction to the Wilsonian effective Lagrangian of an N=2 globally
supersymmetric gauge theory. The renormalisation group beta-function of the
theory crucially allows us to express K(\Psi,\bar\Psi) in a form that easily
generalises to the case in which the theory is coupled to N_F hypermultiplets
in the fundamental representation of the gauge group. This function satisfies
an equation which should be viewed as a fully non-perturbative ``non-chiral
superconformal Ward identity". We also determine its renormalisation group
equation. Furthermore, as a first step towards checking the validity of this
Ansatz, we compute the contribution to K(\Psi,\bar\Psi) from instantons of
winding number k=1 and k=2. As a by-product of our analysis we check a
non-renormalisation theorem for N_F=4.Comment: 39 pages, LaTex file, no figure
Pair Interaction Potentials of Colloids by Extrapolation of Confocal Microscopy Measurements of Collective Structure
A method for measuring the pair interaction potential between colloidal
particles by extrapolation measurement of collective structure to infinite
dilution is presented and explored using simulation and experiment. The method
is particularly well suited to systems in which the colloid is fluorescent and
refractive index matched with the solvent. The method involves characterizing
the potential of mean force between colloidal particles in suspension by
measurement of the radial distribution function using 3D direct visualization.
The potentials of mean force are extrapolated to infinite dilution to yield an
estimate of the pair interaction potential, . We use Monte Carlo (MC)
simulation to test and establish our methodology as well as to explore the
effects of polydispersity on the accuracy. We use poly-12-hydroxystearic
acid-stabilized poly(methyl methacrylate) (PHSA-PMMA) particles dispersed in
the solvent dioctyl phthalate (DOP) to test the method and assess its accuracy
for three different repulsive systems for which the range has been manipulated
by addition of electrolyte.Comment: 35 pages, 14 figure
- …