55 research outputs found
Towards Improved Quantum Simulations and Sensing with Trapped 2D Ion Crystals via Parametric Amplification
Improving coherence is a fundamental challenge in quantum simulation and
sensing experiments with trapped ions. Here we discuss, experimentally
demonstrate, and estimate the potential impacts of two different protocols that
enhance, through motional parametric excitation, the coherent spin-motion
coupling of ions obtained with a spin-dependent force. The experiments are
performed on 2D crystal arrays of approximately one hundred Be ions
confined in a Penning trap. By modulating the trapping potential at close to
twice the center-of-mass mode frequency, we squeeze the motional mode and
enhance the spin-motion coupling while maintaining spin coherence. With a
stroboscopic protocol, we measure dB of motional squeezing below
the ground-state motion, from which theory predicts a dB enhancement in
the sensitivity for measuring small displacements using a recently demonstrated
protocol [Science , 673 (2021)]. With a continuous squeezing
protocol, we measure and accurately calibrate the parametric coupling strength.
Theory suggests this protocol can be used to improve quantum spin squeezing,
limited in our system by off-resonant light scatter. We illustrate numerically
the trade-offs between strong parametric amplification and motional dephasing
in the form of center-of-mass frequency fluctuations for improving quantum spin
squeezing in our set-up.Comment: 11 pages, 6 figure
Comparison of Spontaneous Emission in Trapped Ion Multiqubit Gates at High Magnetic Fields
Penning traps have been used for performing quantum simulations and sensing
with hundreds of ions and provide a promising route toward scaling up trapped
ion quantum platforms because of the ability to trap and control up to
thousands of ions in 2D and 3D crystals. A leading source of decoherence in
laser-based multiqubit operations on trapped ions is off-resonant spontaneous
emission. While many trapped ion quantum computers or simulators utilize clock
qubits, other systems rely on Zeeman qubits, which require a more complex
calculation of this decoherence. We examine theoretically the impacts of
spontaneous emission on quantum gates performed with trapped ions in a high
magnetic field. We consider two types of gates -- light-shift and
Molmer-Sorensen gates -- and compare the decoherence errors in each. We also
compare different detunings, polarizations, and required intensities of the
laser beams used to drive the gates. We show that both gates can have similar
performance at their optimal operating conditions and examine the experimental
feasibility of various operating points. By examining the magnetic field
dependence of each gate, we demonstrate that when the state fine structure
splitting is large compared to the Zeeman splittings, the theoretical
performance of the Molmer-Sorensen gate is significantly better than that of
the light-shift gate. Additionally, for the light-shift gate, we make an
approximate comparison between the fidelities that can be achieved at high
fields with the fidelities of state-of-the-art two-qubit trapped ion quantum
gates. We show that, with regard to spontaneous emission, the achievable
infidelity of our current configuration is about an order of magnitude larger
than that of the best low-field gates, but we also discuss alternative
configurations with potential error rates that are comparable with
state-of-the-art trapped ion gates.Comment: Main text: 19 pages, 13 figures, Appendix: 7 pages, 1 figure, updated
to improve presentatio
Plasmodium malariae in Haitian Refugees, Jamaica
Since 1963, reported malaria transmission in Haiti has been restricted to Plasmodium falciparum. However, screening of Haitian refugees in Jamaica in 2004, by microscopic examination, identified P. falciparum, P. vivax, and P. malariae. PCR confirmed the P. malariae and P. falciparum but not P. vivax infections. DNA sequencing and rRNA gene sequences showed transmission of P. malariae. This report confirms that P. malariae is still being transmitted in Haiti
LSST: from Science Drivers to Reference Design and Anticipated Data Products
(Abridged) We describe here the most ambitious survey currently planned in
the optical, the Large Synoptic Survey Telescope (LSST). A vast array of
science will be enabled by a single wide-deep-fast sky survey, and LSST will
have unique survey capability in the faint time domain. The LSST design is
driven by four main science themes: probing dark energy and dark matter, taking
an inventory of the Solar System, exploring the transient optical sky, and
mapping the Milky Way. LSST will be a wide-field ground-based system sited at
Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m
effective) primary mirror, a 9.6 deg field of view, and a 3.2 Gigapixel
camera. The standard observing sequence will consist of pairs of 15-second
exposures in a given field, with two such visits in each pointing in a given
night. With these repeats, the LSST system is capable of imaging about 10,000
square degrees of sky in a single filter in three nights. The typical 5
point-source depth in a single visit in will be (AB). The
project is in the construction phase and will begin regular survey operations
by 2022. The survey area will be contained within 30,000 deg with
, and will be imaged multiple times in six bands, ,
covering the wavelength range 320--1050 nm. About 90\% of the observing time
will be devoted to a deep-wide-fast survey mode which will uniformly observe a
18,000 deg region about 800 times (summed over all six bands) during the
anticipated 10 years of operations, and yield a coadded map to . The
remaining 10\% of the observing time will be allocated to projects such as a
Very Deep and Fast time domain survey. The goal is to make LSST data products,
including a relational database of about 32 trillion observations of 40 billion
objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures
available from https://www.lsst.org/overvie
Comparing Notes: Recording and Criticism
This chapter charts the ways in which recording has changed the nature of music criticism. It both provides an overview of the history of recording and music criticism, from the advent of Edison’s Phonograph to the present day, and examines the issues arising from this new technology and the consequent transformation of critical thought and practice
Wider Still and Wider: British Music Criticism since the Second World War
This chapter provides the first historical examination of music criticism in Britain since the Second World War. In the process, it also challenges the simplistic prevailing view of this being a period of decline from a golden age in music criticism
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