54 research outputs found
Molecular Feshbach dissociation as a source for motionally entangled atoms
We describe the dissociation of a diatomic Feshbach molecule due to a
time-varying external magnetic field in a realistic trap and guide setting. An
analytic expression for the asymptotic state of the two ultracold atoms is
derived, which can serve as a basis for the analysis of dissociation protocols
to generate motionally entangled states. For instance, the gradual dissociation
by sequences of magnetic field pulses may delocalize the atoms into
macroscopically distinct wave packets, whose motional entanglement can be
addressed interferometrically. The established relation between the applied
magnetic field pulse and the generated dissociation state reveals that
square-shaped magnetic field pulses minimize the momentum spread of the atoms.
This is required to control the detrimental influence of dispersion in a
recently proposed experiment to perform a Bell test in the motion of the two
atoms [C. Gneiting and K. Hornberger, Phys. Rev. Lett. 101, 260503 (2008)].Comment: 12 pages, 3 figures; corresponds to published versio
Effective dynamics of disordered quantum systems
We derive general evolution equations describing the ensemble-average quantum
dynamics generated by disordered Hamiltonians. The disorder average affects the
coherence of the evolution and can be accounted for by suitably tailored
effective coupling agents and associated rates which encode the specific
statistical properties of the Hamiltonian's eigenvectors and eigenvalues,
respectively. Spectral disorder and isotropically disordered eigenvector
distributions are considered as paradigmatic test cases.Comment: 20 page
Quantum phase-space representation for curved configuration spaces
We extend the Wigner-Weyl-Moyal phase-space formulation of quantum mechanics
to general curved configuration spaces. The underlying phase space is based on
the chosen coordinates of the manifold and their canonically conjugate momenta.
The resulting Wigner function displays the axioms of a quasiprobability
distribution, and any Weyl-ordered operator gets associated with the
corresponding phase-space function, even in the absence of continuous
symmetries. The corresponding quantum Liouville equation reduces to the
classical curved space Liouville equation in the semiclassical limit. We
demonstrate the formalism for a point particle moving on two-dimensional
manifolds, such as a paraboloid or the surface of a sphere. The latter
clarifies the treatment of compact coordinate spaces as well as the relation of
the presented phase-space representation to symmetry groups of the
configuration space.Comment: 14 pages. Corresponds to published versio
- …