2,578 research outputs found
Digital Quantum Rabi and Dicke Models in Superconducting Circuits
We propose the analog-digital quantum simulation of the quantum Rabi and
Dicke models using circuit quantum electrodynamics (QED). We find that all
physical regimes, in particular those which are impossible to realize in
typical cavity QED setups, can be simulated via unitary decomposition into
digital steps. Furthermore, we show the emergence of the Dirac equation
dynamics from the quantum Rabi model when the mode frequency vanishes. Finally,
we analyze the feasibility of this proposal under realistic superconducting
circuit scenarios.Comment: 5 pages, 3 figures. Published in Scientific Report
Surface and smectic layering transitions in binary mixtures of parallel hard rods
The surface phase behavior of binary mixtures of colloidal hard rods in
contact with a solid substrate (hard wall) is studied, with special emphasis on
the region of the phase diagram that includes the smectic A phase. The
colloidal rods are modelled as hard cylinders of the same diameter and
different lengths, in the approximation of perfect alignment. A
fundamental--measure density functional is used to obtain equilibrium density
profiles and thermodynamic properties such as surface tensions and adsorption
coefficients. The bulk phase diagram exhibits nematic-smectic and
smectic-smectic demixing, with smectic phases having different compositions; in
some cases they are microfractionated. The calculated surface phase diagram of
the wall-nematic interface shows a very rich phase behavior, including layering
transitions and complete wetting at high pressures, whereby an infinitely thick
smectic film grows at the wall via an infinite sequence of stepwise
first--order layering transitions. For lower pressures complete wetting also
obtains, but here the smectic film grows in a continuous fashion. Finally, at
very low pressures, the wall-nematic interface exhibits critical adsorption by
the smectic phase, due to the second-order character of the bulk
nematic-smectic transition.Comment: 13 pages, 13 figures. Accepted for publication in Physical Review
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