3,060 research outputs found
Preparing and probing atomic number states with an atom interferometer
We describe the controlled loading and measurement of number-squeezed states
and Poisson states of atoms in individual sites of a double well optical
lattice. These states are input to an atom interferometer that is realized by
symmetrically splitting individual lattice sites into double wells, allowing
atoms in individual sites to evolve independently. The two paths then
interfere, creating a matter-wave double-slit diffraction pattern. The time
evolution of the double-slit diffraction pattern is used to measure the number
statistics of the input state. The flexibility of our double well lattice
provides a means to detect the presence of empty lattice sites, an important
and so far unmeasured factor in determining the purity of a Mott state
Driven Macroscopic Quantum Tunneling of Ultracold Atoms in Engineered Optical Lattices
Coherent macroscopic tunneling of a Bose-Einstein condensate between two
parts of an optical lattice separated by an energy barrier is theoretically
investigated. We show that by a pulsewise change of the barrier height, it is
possible to switch between tunneling regime and a self-trapped state of the
condensate. This property of the system is explained by effectively reducing
the dynamics to the nonlinear problem of a particle moving in a double square
well potential. The analysis is made for both attractive and repulsive
interatomic forces, and it highlights the experimental relevance of our
findings
A new method based on noise counting to monitor the frontend electronics of the LHCb muon detector
A new method has been developed to check the correct behaviour of the
frontend electronics of the LHCb muon detector. This method is based on the
measurement of the electronic noise rate at different thresholds of the
frontend discriminator. The method was used to choose the optimal discriminator
thresholds. A procedure based on this method was implemented in the detector
control system and allowed the detection of a small percentage of frontend
channels which had deteriorated. A Monte Carlo simulation has been performed to
check the validity of the method
Muon identification for LHCb Run 3
Muon identification is of paramount importance for the physics programme of
LHCb. In the upgrade phase, starting from Run 3 of the LHC, the trigger of the
experiment will be solely based on software. The luminosity increase to
cms will require an improvement of the muon
identification criteria, aiming at performances equal or better than those of
Run 2, but in a much more challenging environment. In this paper, two new muon
identification algorithms developed in view of the LHCb upgrade are presented,
and their performance in terms of signal efficiency versus background reduction
is shown
Nonlinear Dynamics in Double Square Well Potential
Considering the coherent nonlinear dynamics in double square well potential
we find the example of coexistence of Josephson oscillations with a
self-trapping regime. This macroscopic bistability is explained by proving
analytically the simultaneous existence of symmetric, antisymmetric and
asymmetric stationary solutions of the associated Gross-Pitaevskii equation.
The effect is illustrated and confirmed by numerical simulations. This property
allows to make suggestions on possible experiments using Bose-Einstein
condensates in engineered optical lattices or weakly coupled optical waveguide
arrays
Related peripheral blood stem cell donors experience more severe symptoms and less complete recovery at one year compared to unrelated donors
Atomic micromotion and geometric forces in a triaxial magnetic trap
Non-adiabatic motion of Bose-Einstein condensates of rubidium atoms arising
from the dynamical nature of a time-orbiting-potential (TOP) trap was observed
experimentally. The orbital micromotion of the condensate in velocity space at
the frequency of the rotating bias field of the TOP was detected by a
time-of-flight method. A dependence of the equilibrium position of the atoms on
the sense of rotation of the bias field was observed. We have compared our
experimental findings with numerical simulations. The nonadiabatic following of
the atomic spin in the trap rotating magnetic field produces geometric forces
acting on the trapped atoms.Comment: 4 pages, 4 figure
Adding control to arbitrary unknown quantum operations
While quantum computers promise significant advantages, the complexity of
quantum algorithms remains a major technological obstacle. We have developed
and demonstrated an architecture-independent technique that simplifies adding
control qubits to arbitrary quantum operations-a requirement in many quantum
algorithms, simulations and metrology. The technique is independent of how the
operation is done, does not require knowledge of what the operation is, and
largely separates the problems of how to implement a quantum operation in the
laboratory and how to add a control. We demonstrate an entanglement-based
version in a photonic system, realizing a range of different two-qubit gates
with high fidelity.Comment: 9 pages, 8 figure
China and the crisis : global power, domestic caution and local initiative
Even though the global crisis had a quick and dramatic impact on Chinese exports, the Chinese government responded with a range of policy responses that have helped maintain high rates of growth. This success has helped propel China to the centre of global politics, accelerating what many perceive to be a power shift from the West to China. But these gains were achieved by reversing policy in previous years designed to make a fundamental shift in China‟s mode of development, and have highlighted the problems associated with making such a transition. At the moment that many are looking at the Chinese "model" as a potential alternative to the Washington Consensus, one of the consequences of the crisis is to further question the long term efficacy of this "model" in China itself
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