45,531 research outputs found
Renormalization group approach to spinor Bose-Fermi mixtures in a shallow optical lattice
We study a mixture of ultracold spin-half fermionic and spin-one bosonic
atoms in a shallow optical lattice where the bosons are coupled to the fermions
via both density-density and spin-spin interactions. We consider the parameter
regime where the bosons are in a superfluid ground state, integrate them out,
and obtain an effective action for the fermions. We carry out a renormalization
group analysis of this effective fermionic action at low temperatures, show
that the presence of the spinor bosons may lead to a separation of Fermi
surfaces of the spin-up and spin-down fermions, and investigate the parameter
range where this phenomenon occurs. We also calculate the susceptibilities
corresponding to the possible superfluid instabilities of the fermions and
obtain their possible broken-symmetry ground states at low temperatures and
weak interactions.Comment: 8 pages, 8 figs v
Pairing and density-wave phases in Boson-Fermion mixtures at fixed filling
We study a mixture of fermionic and bosonic cold atoms on a two-dimensional
optical lattice, where the fermions are prepared in two hyperfine (isospin)
states and the bosons have Bose-Einstein condensed (BEC). The coupling between
the fermionic atoms and the bosonic fluctuations of the BEC has similarities
with the electron-phonon coupling in crystals. We study the phase diagram for
this system at fixed fermion density of one per site (half-filling). We find
that tuning of the lattice parameters and interaction strengths (for
fermion-fermion, fermion-boson and boson-boson interactions) drives the system
to undergo antiferromagnetic ordering, s-wave and d-wave pairing
superconductivity or a charge density wave phase. We use functional
renormalization group analysis where retardation effects are fully taken into
account by keeping the frequency dependence of the interaction vertices and
self-energies. We calculate response functions and also provide estimates of
the energy gap associated with the dominant order, and how it depends on
different parameters of the problem.Comment: 5 pages, 3 figure
Digital Switching in the Quantum Domain
In this paper, we present an architecture and implementation algorithm such
that digital data can be switched in the quantum domain. First we define the
connection digraph which can be used to describe the behavior of a switch at a
given time, then we show how a connection digraph can be implemented using
elementary quantum gates. The proposed mechanism supports unicasting as well as
multicasting, and is strict-sense non-blocking. It can be applied to perform
either circuit switching or packet switching. Compared with a traditional space
or time domain switch, the proposed switching mechanism is more scalable.
Assuming an n-by-n quantum switch, the space consumption grows linearly, i.e.
O(n), while the time complexity is O(1) for unicasting, and O(log n) for
multicasting. Based on these advantages, a high throughput switching device can
be built simply by increasing the number of I/O ports.Comment: 24 pages, 16 figures, LaTe
Microfluidic immunomagnetic multi-target sorting – a model for controlling deflection of paramagnetic beads
We describe a microfluidic system that uses a magnetic field to sort paramagnetic beads by deflecting them in the direction normal to the flow. Our experiments systematically study the dependence of the beads’ deflection on: bead size and susceptibility, magnet strength, fluid speed and viscosity, and device geometry. We also develop a design parameter that can aid in the design of microfluidic devices for immunomagnetic multi-target sorting
Remote sensing of sea state by laser altimeters
The reflection of short laser pulses from the ocean surface was analyzed based on the specular point theory of scattering. The expressions for the averaged received signal, shot noise and speckle induced noise were derived for a direct detection system. It is found that the reflected laser pulses have an average shape closely related to the probability density function associated with the surface profile. This result is applied to estimate the mean sea level and significant wave height from the receiver output of the laser altimeter
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