64 research outputs found
Large parity violating effects in atomic dysprosium with nearly degenerate Floquet eigenvalues
In this article we study effects of parity nonconservation in atomic
dysprosium, where one has a pair of nearly degenerate levels of opposite
parity. We consider the time evolution of this two-level system within
oscillatory electric and magnetic fields. These are chosen to have a periodical
structure with the same period, such that a Floquet matrix describes the time
evolution of the quantum states. We show that, if the states are unstable, the
eigenvalues of the Floquet matrix may have contributions proportional to the
square root of the parity violating interaction matrix element while they
are almost degenerate in their parity even part. This leads to beat frequencies
proportional to which are expected to be larger by several orders
of magnitude compared to ordinary P-violating contributions which are of order
. However, for the simple field configurations we considered, it still
seems to be difficult to observe these P-violating beat effects, since the
states decay too fast. On the other hand, we found that, within only a few
Floquet cycles, very large parity violating asymmetries with respect to
experimental setups of opposite chirality may be obtained. The electric and
magnetic fields as well as the time intervals necessary for this are in an
experimentally accessible range. For statistically significant effects beyond
one standard deviation a number of about atoms is required. Our ideas
may be applied directly to other 2-level atomic systems and different field
configurations. We hope that these ideas will stimulate experimental work in
this direction.Comment: Sep 1999, 29pp, 10 Fig
Long-range nature of Feshbach molecules in Bose-Einstein condensates
We discuss the long-range nature of the molecules produced in recent experiments on molecular Bose-Einstein condensation. The properties of these molecules depend on the full two-body Hamiltonian and not just on the states of the system in the absence of interchannel couplings. The very long-range nature of the state is crucial to the efficiency of production in the experiments. Our many-body treatment of the gas accounts for the full binary physics and describes properly how these molecular condensates can be directly probed
Free expansion of a Lieb-Liniger gas: Asymptotic form of the wave functions
The asymptotic form of the wave functions describing a freely expanding
Lieb-Liniger gas is derived by using a Fermi-Bose transformation for
time-dependent states, and the stationary phase approximation. We find that
asymptotically the wave functions approach the Tonks-Girardeau (TG) structure
as they vanish when any two of the particle coordinates coincide. We point out
that the properties of these asymptotic states can significantly differ from
the properties of a TG gas in a ground state of an external potential. The
dependence of the asymptotic wave function on the initial state is discussed.
The analysis encompasses a large class of initial conditions, including the
ground states of a Lieb-Liniger gas in physically realistic external
potentials. It is also demonstrated that the interaction energy asymptotically
decays as a universal power law with time, .Comment: Section VI added to v2; published versio
Matter Wave Turbulence: Beyond Kinetic Scaling
Turbulent scaling phenomena are studied in an ultracold Bose gas away from
thermal equilibrium. Fixed points of the dynamical evolution are characterized
in terms of universal scaling exponents of correlation functions. The scaling
behavior is determined analytically in the framework of quantum field theory,
using a nonperturbative approximation of the two-particle irreducible effective
action. While perturbative Kolmogorov scaling is recovered at higher energies,
scaling solutions with anomalously large exponents arise in the infrared regime
of the turbulence spectrum. The extraordinary enhancement in the momentum
dependence of long-range correlations could be experimentally accessible in
dilute ultracold atomic gases. Such experiments have the potential to provide
insight into dynamical phenomena directly relevant also in other present-day
focus areas like heavy-ion collisions and early-universe cosmology.Comment: 18 pages, 2 figure
Dynamic formation of Rydberg aggregates at off-resonant excitation
The dynamics of a cloud of ultra-cold two-level atoms is studied at
off-resonant laser driving to a Rydberg state. We find that resonant excitation
channels lead to strongly peaked spatial correlations associated with the
buildup of asymmetric excitation structures. These aggregates can extend over
the entire ensemble volume, but are in general not localized relative to the
system boundaries. The characteristic distances between neighboring excitations
depend on the laser detuning and on the interaction potential. These properties
lead to characteristic features in the spatial excitation density, the Mandel
parameter, and the total number of excitations. As an application an
implementation of the three-atom CSWAP or Fredkin gate with Rydberg atoms is
discussed. The gate not only exploits the Rydberg blockade, but also utilizes
the special features of an asymmetric geometric arrangement of the three atoms.
We show that continuous-wave off-resonant laser driving is sufficient to create
the required spatial arrangement of atoms out of a homogeneous cloud.Comment: 8 pages, 7 figure
Fermi-Bose transformation for the time-dependent Lieb-Liniger gas
Exact solutions of the Schrodinger equation describing a freely expanding
Lieb-Liniger (LL) gas of delta-interacting bosons in one spatial dimension are
constructed. The many-body wave function is obtained by transforming a fully
antisymmetric (fermionic) time-dependent wave function which obeys the
Schrodinger equation for a free gas. This transformation employs a differential
Fermi-Bose mapping operator which depends on the strength of the interaction
and the number of particles.Comment: 4+ pages, 1 figure; added reference
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