699 research outputs found
Spinor Dynamics-Driven Formation of a Dual-Beam Atom Laser
We demonstrate a novel dual-beam atom laser formed by outcoupling oppositely
polarized components of an F=1 spinor Bose-Einstein condensate whose Zeeman
sublevel populations have been coherently evolved through spin dynamics. The
condensate is formed through all-optical means using a single-beam running-wave
dipole trap. We create a condensate in the field-insensitive state, and
drive coherent spin-mixing evolution through adiabatic compression of the
initially weak trap. Such dual beams, number-correlated through the angular
momentum-conserving reaction , have been
proposed as tools to explore entanglement and squeezing in Bose-Einstein
condensates, and have potential use in precision phase measurements.Comment: 4 pages, 4 figure
Synthetic clock transitions via continuous dynamical decoupling
Decoherence of quantum systems due to uncontrolled fluctuations of the
environment presents fundamental obstacles in quantum science. `Clock'
transitions which are insensitive to such fluctuations are used to improve
coherence, however, they are not present in all systems or for arbitrary system
parameters. Here, we create a trio of synthetic clock transitions using
continuous dynamical decoupling in a spin-1 Bose-Einstein condensate in which
we observe a reduction of sensitivity to magnetic field noise of up to four
orders of magnitude; this work complements the parallel work by Anderson et al.
(submitted, 2017). In addition, using a concatenated scheme, we demonstrate
suppression of sensitivity to fluctuations in our control fields. These
field-insensitive states represent an ideal foundation for the next generation
of cold atom experiments focused on fragile many-body phases relevant to
quantum magnetism, artificial gauge fields, and topological matter.Comment: 8 pages, 4 figures, Supplemental material
Differential Light Shift Cancellation in a Magnetic-Field-Insensitive Transition of Rb
We demonstrate near-complete cancellation of the differential light shift of
a two-photon magnetic-field-insensitive microwave hyperfine (clock) transition
in Rb atoms trapped in an optical lattice. Up to of the
differential light shift is canceled while maintaining magnetic-field
insensitivity. This technique should have applications in quantum information
and frequency metrology.Comment: 5 pages, 4 figure
Observations of structure in a low-loss radiofrequency-dressed optical lattice
We load a Bose-Einstein condensate into a one-dimensional (1D) optical
lattice altered through the use of radiofrequency (rf) dressing. The rf
resonantly couples the three levels of the Rb manifold and
combines with a spin-dependent "bare" optical lattice to result in adiabatic
potentials of variable shape, depth, and spatial frequency content. We choose
dressing parameters such that the altered lattice is stable over lifetimes
exceeding tens of ms at higher depths than in previous work. We observe
significant differences between the BEC momentum distributions of the dressed
lattice as compared to the bare lattice, and find general agreement with a 1D
band structure calculation informed by the dressing parameters. Previous work
using such lattices was limited by very shallow dressed lattices and strong
Landau-Zener tunnelling loss between adiabatic potentials, equivalent to
failure of the adiabatic criterion. In this work we operate with significantly
stronger rf coupling (increasing the avoided-crossing gap between adiabatic
potentials), observing dressed lifetimes of interest for optical lattice-based
analogue solid-state physics.Comment: 5 pages, 3 figure
Shell potentials for microgravity Bose-Einstein condensates
Extending the understanding of Bose-Einstein condensate (BEC) physics to new
geometries and topologies has a long and varied history in ultracold atomic
physics. One such new geometry is that of a bubble, where a condensate would be
confined to the surface of an ellipsoidal shell. Study of this geometry would
give insight into new collective modes, self-interference effects,
topology-dependent vortex behavior, dimensionality crossovers from thick to
thin shells, and the properties of condensates pushed into the ultradilute
limit. Here we discuss a proposal to implement a realistic experimental
framework for generating shell-geometry BEC using radiofrequency dressing of
magnetically-trapped samples. Such a tantalizing state of matter is
inaccessible terrestrially due to the distorting effect of gravity on
experimentally-feasible shell potentials. The debut of an orbital BEC machine
(NASA Cold Atom Laboratory, aboard the International Space Station) has enabled
the operation of quantum-gas experiments in a regime of perpetual freefall, and
thus has permitted the planning of microgravity shell-geometry BEC experiments.
We discuss specific experimental configurations, applicable inhomogeneities and
other experimental challenges, and outline potential experiments.Comment: 6 pages, 3 figure
Modulation of telomere terminal structure by telomerase components in Candida albicans
The telomerase ribonucleoprotein in Candida albicans is presumed to contain at least three Est proteins: CaEst1p, CaEst2p/TERT and CaEst3p. We constructed mutants missing each of the protein subunit of telomerase and analyzed overall telomere dynamics and single-stranded telomere overhangs over the course of many generations. The est1-ΔΔ mutant manifested abrupt telomere loss and recovery, consistent with heightened recombination. Both the est2-ΔΔ and est3-ΔΔ mutant exhibited progressive telomere loss, followed by the gradual emergence of survivors with long telomeres. In no case was telomere loss accompanied by severe growth defects, suggesting that cells with short telomeres can continue to proliferate. Furthermore, the amount of G-strand terminal overhangs was greatly increased in the est2-ΔΔ mutant, but not others. Our results suggest that in addition to their well-characterized function in telomere elongation, both CaEst1p and CaEst2p mediate some aspects of telomere protection in Candida, with the former suppressing excessive recombination, and the latter preventing excessive C-strand degradation
Atoms in a radiofrequency-dressed optical lattice
We load cold atoms into an optical lattice dramatically reshaped by
radiofrequency (rf) coupling of state-dependent lattice potentials. This rf
dressing changes the unit cell of the lattice at a subwavelength scale, such
that its curvature and topology departs strongly from that of a simple
sinusoidal lattice potential. Radiofrequency dressing has previously been
performed at length scales from mm to tens of microns, but not at the
single-optical-wavelength scale. At this length scale significant coupling
between adiabatic potentials leads to nonadiabatic transitions, which we
measure as a function of lattice depth and dressing frequency and amplitude. We
also investigate the dressing by measuring changes in the momentum distribution
of the dressed states.Comment: 5 pages, 4 figure
Comment on ''Long-Term Effects of Diesel Exhaust Particles on Airway Inflammation and Remodeling in a Mouse Model" by Kim et al.
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