770 research outputs found
Defect-Suppressed Atomic Crystals in an Optical Lattice
We present a coherent filtering scheme which dramatically reduces the site
occupation number defects for atoms in an optical lattice, by transferring a
chosen number of atoms to a different internal state via adiabatic passage.
With the addition of superlattices it is possible to engineer states with a
specific number of atoms per site (atomic crystals), which are required for
quantum computation and the realisation of models from condensed matter
physics, including doping and spatial patterns. The same techniques can be used
to measure two-body spatial correlation functions. We illustrate these ideas
with a scheme to study the creation of a BCS state with a chosen filling factor
from a degenerate Fermi gas in an optical lattice.Comment: 4 Pages, 5 Figures, REVTex
BDGS: A Scalable Big Data Generator Suite in Big Data Benchmarking
Data generation is a key issue in big data benchmarking that aims to generate
application-specific data sets to meet the 4V requirements of big data.
Specifically, big data generators need to generate scalable data (Volume) of
different types (Variety) under controllable generation rates (Velocity) while
keeping the important characteristics of raw data (Veracity). This gives rise
to various new challenges about how we design generators efficiently and
successfully. To date, most existing techniques can only generate limited types
of data and support specific big data systems such as Hadoop. Hence we develop
a tool, called Big Data Generator Suite (BDGS), to efficiently generate
scalable big data while employing data models derived from real data to
preserve data veracity. The effectiveness of BDGS is demonstrated by developing
six data generators covering three representative data types (structured,
semi-structured and unstructured) and three data sources (text, graph, and
table data)
Two-dimensional Lattice Gauge Theories with Superconducting Quantum Circuits
A quantum simulator of U(1) lattice gauge theories can be implemented with
superconducting circuits. This allows the investigation of confined and
deconfined phases in quantum link models, and of valence bond solid and spin
liquid phases in quantum dimer models. Fractionalized confining strings and the
real-time dynamics of quantum phase transitions are accessible as well. Here we
show how state-of-the-art superconducting technology allows us to simulate
these phenomena in relatively small circuit lattices. By exploiting the strong
non-linear couplings between quantized excitations emerging when
superconducting qubits are coupled, we show how to engineer gauge invariant
Hamiltonians, including ring-exchange and four-body Ising interactions. We
demonstrate that, despite decoherence and disorder effects, minimal circuit
instances allow us to investigate properties such as the dynamics of electric
flux strings, signaling confinement in gauge invariant field theories. The
experimental realization of these models in larger superconducting circuits
could address open questions beyond current computational capability.Comment: Published versio
Strong magnetic coupling between an electronic spin qubit and a mechanical resonator
We describe a technique that enables a strong, coherent coupling between a
single electronic spin qubit associated with a nitrogen-vacancy impurity in
diamond and the quantized motion of a magnetized nano-mechanical resonator tip.
This coupling is achieved via careful preparation of dressed spin states which
are highly sensitive to the motion of the resonator but insensitive to
perturbations from the nuclear spin bath. In combination with optical pumping
techniques, the coherent exchange between spin and motional excitations enables
ground state cooling and the controlled generation of arbitrary quantum
superpositions of resonator states. Optical spin readout techniques provide a
general measurement toolbox for the resonator with quantum limited precision
Long-Term Stability of Planets in Binary Systems
A simple question of celestial mechanics is investigated: in what regions of
phase space near a binary system can planets persist for long times? The
planets are taken to be test particles moving in the field of an eccentric
binary system. A range of values of the binary eccentricity and mass ratio is
studied, and both the case of planets orbiting close to one of the stars, and
that of planets outside the binary orbiting the system's center of mass, are
examined. From the results, empirical expressions are developed for both 1) the
largest orbit around each of the stars, and 2) the smallest orbit around the
binary system as a whole, in which test particles survive the length of the
integration (10^4 binary periods). The empirical expressions developed, which
are roughly linear in both the mass ratio mu and the binary eccentricity e, are
determined for the range 0.0 <= e <= 0.7-0.8 and 0.1 <= mu <= 0.9 in both
regions, and can be used to guide searches for planets in binary systems. After
considering the case of a single low-mass planet in binary systems, the
stability of a mutually-interacting system of planets orbiting one star of a
binary system is examined, though in less detail.Comment: 19 pages, 5 figures, 7 tables, accepted by the Astronomical Journa
Precision radial velocities of double-lined spectroscopic binaries with an iodine absorption cell
A spectroscopic technique employing an iodine absorption cell (I_2) to
superimpose a reference spectrum onto a stellar spectrum is currently the most
widely adopted approach to obtain precision radial velocities of solar-type
stars. It has been used to detect ~80 extrasolar planets out of ~130 know. Yet
in its original version, it only allows us to measure precise radial velocities
of single stars. In this paper, we present a novel method employing an I_2
absorption cell that enables us to accurately determine radial velocities of
both components of double-lined binaries. Our preliminary results based on the
data from the Keck I telescope and HIRES spectrograph demonstrate that 20-30
m/s radial velocity precision can be routinely obtained for "early" type
binaries (F3-F8). For later type binaries, the precision reaches ~10 m/s. We
discuss applications of the technique to stellar astronomy and searches for
extrasolar planets in binary systems. In particular, we combine the
interferometric data collected with the Palomar Testbed Interferometer with our
preliminary precision velocities of the spectroscopic double-lined binary HD
4676 to demonstrate that with such a combination one can routinely obtain
masses of the binary components accurate at least at the level of 1.0%.Comment: Accepted for publication in The Astrophysical Journa
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