9,116 research outputs found
Quantum Theory of a Resonant Photonic Crystal
We present a quantum model of two-level atoms localized in a 3D lattice,
based on the Hopfield theory of exciton polaritons. In addition to a
polaritonic gap at the exciton energy, a photonic bandgap opens up at the
Brillouin zone boundary. Upon tuning the lattice period or angle of incidence
to match the photonic gap with the exciton energy, one obtains a combined
polaritonic and photonic gap as a generalization of Rabi splitting. For typical
experimental parameters, the size of the combined gap is on the order of 25
cm^{-1}, up to 10^5 times the detuned gap size. The dispersion curve contains a
branch supporting slow-light modes with vanishing exciton probability density.Comment: 4 pages, 3 figure
Measurement of Holmium Rydberg series through MOT depletion spectroscopy
We report measurements of the absolute excitation frequencies of Ho
and odd-parity Rydberg series. The states are
detected through depletion of a magneto-optical trap via a two-photon
excitation scheme. Measurements of 162 Rydberg levels in the range
yield quantum defects well described by the Rydberg-Ritz formula. We observe a
strong perturbation in the series around due to an unidentified
interloper at 48515.47(4) cm. From the series convergence, we determine
the first ionization potential cm, which is
three orders of magnitude more accurate than previous work. This work
represents the first time such spectroscopy has been done in Holmium and is an
important step towards using Ho atoms for collective encoding of a quantum
register.Comment: 6 figure
Atom interferometry with Bose-Einstein condensates in a double-well potential
A trapped-atom interferometer was demonstrated using gaseous Bose-Einstein
condensates coherently split by deforming an optical single-well potential into
a double-well potential. The relative phase between the two condensates was
determined from the spatial phase of the matter wave interference pattern
formed upon releasing the condensates from the separated potential wells.
Coherent phase evolution was observed for condensates held separated by 13
m for up to 5 ms and was controlled by applying ac Stark shift potentials
to either of the two separated condensates.Comment: 4 pages, 4 figure
Do structured methods help eco-innovation: An evaluation of the product ideas tree diagram
This paper reports on the first test of the Product Ideas Tree diagram (PIT): a structured method aimed to help Eco-innovation. The PIT diagram structures ideas output from chaotic idea generating sessions. This study compared four ways of conducting an Eco-innovation workshop. The results show that structured methods help Eco-innovation by improving the constructive communication between the participants. Further development of the PIT diagram promises to contribute several new approaches to sustainable product and process design
Contrast Interferometry Using Bose-Einstein Condensates to Measure h/m and the Fine Structure Constant
The kinetic energy of an atom recoiling due to absorption of a photon was
measured as a frequency using an interferometric technique called ``contrast
interferometry''. Optical standing wave pulses were used as atom-optical
elements to create a symmetric three-path interferometer with a Bose-Einstein
condensate. The recoil phase accumulated in different paths was measured using
a single-shot detection technique. The scheme allows for additional photon
recoils within the interferometer and its symmetry suppresses several random
and systematic errors including those from vibrations and ac Stark shifts. We
have measured the photon recoil frequency of sodium to ppm precision, using
a simple realization of this scheme. Plausible extensions should yield a
sufficient precision to bring within reach a ppb-level determination of
and the fine structure constant
Distillation of Bose-Einstein condensates in a double-well potential
Bose-Einstein condensates of sodium atoms, prepared in an optical dipole
trap, were distilled into a second empty dipole trap adjacent to the first one.
The distillation was driven by thermal atoms spilling over the potential
barrier separating the two wells and then forming a new condensate. This
process serves as a model system for metastability in condensates, provides a
test for quantum kinetic theories of condensate formation, and also represents
a novel technique for creating or replenishing condensates in new locations
Demonstration of an inductively coupled ring trap for cold atoms
We report the first demonstration of an inductively coupled magnetic ring trap for cold atoms. A uniform, ac magnetic field is used to induce current in a copper ring, which creates an opposing magnetic field that is time-averaged to produce a smooth cylindrically symmetric ring trap of radius 5 mm. We use a laser-cooled atomic sample to characterize the loading efficiency and adiabaticity of the magnetic potential, achieving a vacuum-limited lifetime in the trap. This technique is suitable for creating scalable toroidal waveguides for applications in matter-wave interferometry, offering long interaction times and large enclosed areas
Physical oceanographic investigations in the Eastern Bering and Chukchi Seas during the summer of 1947
New information on the physical properties of the waters in the eastern Bering and Chukchi seas is discussed. It shows that, in summer, the water masses of this area are complicated by the circulation and advective processes. In general, the southern Bering Sea water flows northward and is modified by warm low-salinity water from rivers along the Alaskan coast and from intrusions of cold high-salinity water from the western Bering Sea. This mixture of water funn els through the Bering Strait principally at the surface on the eastern side...
A method for determining mean longitudinal velocities in a coastal plain estuary
It is shown that the longitudinal component of the mean velocity in a coastal plain estuary may be computed by indirect methods. To do this, use is made of the lateral and longitudinal components of the equation of motion, the tidal velocity amplitudes, and a deduced relationship between the vertical and lateral eddy stresses. The method is evaluated for a station in the James River estuary. The resultant computed velocities agree quantitatively with the corresponding observed velocities
A test of mixing length theories in a coastal plain estuary
Observations of vertical and horizontal variations in salinity and velocity in the James River estuary have been previously employed in the indirect determination of the vertical eddy flux of salt
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