A representation is put forward for wave functions of quantum particles in
periodic lattice potentials subjected to homogeneous time-periodic forcing,
based on an expansion with respect to Bloch-like states which embody both the
spatial and the temporal periodicity. It is shown that there exists a
generalization of Bloch's famous acceleration theorem which grows out of this
representation and captures the effect of a weak probe force applied in
addition to a strong dressing force. Taken together, these elements point at a
"dressing and probing" strategy for coherent wave-packet manipulation, which
could be implemented in present experiments with optical lattices.Comment: 12 pages, 4 figure
We argue that ultracold atoms in strongly shaken optical lattices can be
subjected to conditions similar to those experienced by electrons in
laser-irradiated crystalline solids, but without introducing secondary
polarization effects. As a consequence one can induce nonperturbative
multiphoton-like resonances due to the mutual penetration of ac-Stark-shifted
Bloch bands. These phenomena can be detected with a combination of currently
available laboratory techniques.Comment: 5 pages, 5 figure
In a parameter regime for which the mean-field (Gross-Pitaevskii) dynamics becomes chaotic, mesoscopic quantum superpositions in phase space can occur in a double-well potential which is shaken periodically. For experimentally realistic initial states like the ground state of some 100 atoms, the emergence of mesoscopic quantum superpositions in phase space is investigated numerically. It is shown to be reproducible even if the initial conditions slightly change. While the final state is not a perfect superposition of two distinct phase-states, the superposition is reached an order of magnitude faster than in the case of the collapse and revival phenomenon. Furthermore, a generator of entanglement is identified.
Motivated by recent experimental progress achieved with ultracold atoms in
kilohertz-driven optical lattices, we provide a theoretical discussion of
mechanisms governing the response of a particle in a cosine lattice potential
to strong forcing pulses with smooth envelope. Such pulses effectuate adiabatic
motion of a wave packet's momentum distribution on quasienergy surfaces created
by spatiotemporal Bloch waves. Deviations from adiabaticity can then
deliberately be exploited for exerting coherent control and for reaching target
states which may not be accessible by other means. As one particular example,
we consider an analog of the \pi-pulses known from optical resonance. We also
suggest adapting further techniques previously developed for controlling atomic
and molecular dynamics by laser pulses to the coherent control of matter waves
in shaken optical lattices.Comment: 11 pages, 10 figure
Time-of-flight (TOF) magnetic sensing of rolling immunomagnetically-labeled cells offers great potential for single cell function analysis at the bedside in even optically opaque media, such as whole blood. However, due to the spatial resolution of the sensor and the low flow rate regime required to observe the behavior of rolling cells, the concentration range of such a workflow is limited. Potential clinical applications, such as testing of leukocyte function, require a cytometer which can cover a cell concentration range of several orders of magnitude. This is a challenging task for an integrated dilution-free workflow, as for high cell concentrations coincidences need to be avoided, while for low cell concentrations sufficient statistics should be provided in a reasonable time-to-result. Here, we extend the spatial bandwidth of a magnetoresistive sensor with an adaptive and integratable workflow concept combining mechanical and magnetophoretic guiding of magnetically labeled targets for in-situ enrichment over a dynamic concentration range of 3 orders of magnitude. We achieve hybrid integration of the enrichment strategy in a cartridge mold and a giant-magnetoresistance (GMR) sensor in a functionalized Quad Flat No-Lead (QFN) package, which allows for miniaturization of the Si footprint for potential low-cost bedside testing. The enrichment results demonstrate that TOF magnetic flow cytometry with adaptive particle focusing can match the clinical requirements for a point-of-care (POC) cytometer and can potentially be of interest for other sheath-less methodologies requiring workflow integration.
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