16,115 research outputs found
Disorder effects on the quantum coherence of a many-boson system
The effects of disorders on the quantum coherence for many-bosons are studied
in a double well model. For the ground state, the disorder enhances the quantum
coherence. In the deep Mott regime, dynamical evolution reveals periodical
collapses and revivals of the quantum coherence which is robust against the
disorder. The average over variations in both the on-site energy and the
interaction reveals a beat phenomenon of the coherence-decoherence oscillation
in the temporal evolution.Comment: 4 figure
Quantum gates with weak van der Waals interactions of neutral Rydberg atoms
Neutral atoms are promising for large-scale quantum computing, but accurate
neutral-atom entanglement depends on large Rydberg interactions which strongly
limit the interatomic distances. Via a phase accumulation in detuned Rabi
cycles enabled by a Rydberg interaction of similar magnitude to the Rydberg
Rabi frequency, we study a controlled-phase gate with an arbitrary phase and
extend it to the controlled-NOT gate. The gates need only three steps for
coupling one Rydberg state, depend on easily accessible van der Waals
interaction that naturally arises between distant atoms, and have no rotation
error in the weak interaction regime. Importantly, they can work with very weak
interactions so that well-separated qubits can be entangled. The gates are
sensitive to the irremovable fluctuation of Rydberg interactions, but can still
have a fidelity over 98\% with realistic position fluctuation of qubits
separated over 20~m.Comment: 7 pages, 3 figure
Revealing the cosmic web dependent halo bias
Halo bias is the one of the key ingredients of the halo models. It was shown
at a given redshift to be only dependent, to the first order, on the halo mass.
In this study, four types of cosmic web environments: clusters, filaments,
sheets and voids are defined within a state of the art high resolution -body
simulation. Within those environments, we use both halo-dark matter
cross-correlation and halo-halo auto correlation functions to probe the
clustering properties of halos. The nature of the halo bias differs strongly
among the four different cosmic web environments we describe. With respect to
the overall population, halos in clusters have significantly lower biases in
the {} mass range. In other
environments however, halos show extremely enhanced biases up to a factor 10 in
voids for halos of mass {}. Such a strong
cosmic web environment dependence in the halo bias may play an important role
in future cosmological and galaxy formation studies. Within this cosmic web
framework, the age dependency of halo bias is found to be only significant in
clusters and filaments for relatively small halos \la 10^{12.5}\msunh.Comment: 14 pages, 14 figures, ApJ accepte
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