380 research outputs found
Theory of RF-spectroscopy of strongly interacting Fermions
We show that strong pairing correlations in Fermi gases lead to the
appearance of a gap-like structure in the RF-spectrum, both in the balanced
superfluid and in the normal phase above the Clogston-Chandrasekhar limit. The
average RF-shift of a unitary gas is proportional to the ratio of the Fermi
velocity and the scattering length with the final state. In the strongly
imbalanced case, the RF-spectrum measures the binding energy of a minority atom
to the Fermi sea of majority atoms. Our results provide a qualitative
understanding of recent experiments by Schunck et.al.Comment: revised version, 4 pages, 3 figures, RevTex
Extended Bose-Hubbard model with incompressible states at fractional numbers
The Bose-Hubbard model is extended to include nearest and far neighbor
interactions and is related to the fractional quantum Hall effect (FQHE). Both
models may be studied in optical lattices with quantum gases. The ground state
is calculated for the extended Bose-Hubbard model with strong repulsive
interactions (weak hopping). Incompressible Mott insulator states are found at
rational filling fractions compatible with the principal and secondary FQHE
filling fractions of the lowest Landau levels observed experimentally. It is
discussed to which extent these states at fractional filling survive or
undergoes a Mott insulator transition to a superfluid as hopping terms are
included.Comment: Revised version, to appear in PR
Spatial correlations of trapped 1d bosons in an optical lattice
We investigate a quasi-one dimensional system of trapped cold bosonic atoms
in an optical lattice by using the density matrix renormalization group to
study the Bose-Hubbard model at T=0 for experimentally realistic numbers of
lattice sites. It is shown that a properly rescaled one-particle density matrix
characterizes superfluid versus insulating states just as in the homogeneous
system. For typical parabolic traps we also confirm the widely used local
density approach for describing correlations in the limit of weak interaction.
Finally, we note that the superfluid to Mott-insulating transition is seen most
directly in the half width of the interference peak
Long-range big quantum-data transmission
We introduce an alternative type of quantum repeater for long-range quantum
communication with improved scaling with the distance. We show that by
employing hashing, a deterministic entanglement distillation protocol with
one-way communication, one obtains a scalable scheme that allows one to reach
arbitrary distances, with constant overhead in resources per repeater station,
and ultrahigh rates. In practical terms, we show that also with moderate
resources of a few hundred qubits at each repeater station, one can reach
intercontinental distances. At the same time, a measurement-based
implementation allows one to tolerate high loss, but also operational and
memory errors of the order of several percent per qubit. This opens the way for
long-distance communication of big quantum data.Comment: revised manuscript including new result
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