49 research outputs found
Quantum Correlations in Two-Particle Anderson Localization
We predict the quantum correlations between non-interacting particles
evolving simultaneously in a disordered medium. While the particle density
follows the single-particle dynamics and exhibits Anderson localization, the
two-particle correlation develops unique features that depend on the quantum
statistics of the particles and their initial separation. On short time scales,
the localization of one particle becomes dependent on whether the other
particle is localized or not. On long time scales, the localized particles show
oscillatory correlations within the localization length. These effects can be
observed in Anderson localization of non-classical light and ultra-cold atoms.Comment: 4 pages, 4 figures, comments welcom
Aging on the edge of stability in disordered systems
Many complex and disordered systems fail to reach equilibrium after they have
been quenched or perturbed. Instead, they sluggishly relax toward equilibrium
at an ever-slowing, history-dependent rate, a process termed physical aging.
The microscopic processes underlying the dynamic slow-down during aging and the
reason for its similar occurrence in different systems remain poorly
understood. Here, through experiments in crumpled sheets and simulations of a
minimal mechanical model - a disordered network of bi-stable elastic elements -
we reveal the structural mechanism underlying logarithmic aging in this system.
We show that under load, the system self-organizes to a metastable state poised
on the verge of an instability, where it can remain for long, but finite times.
The system's relaxation is intermittent, advancing via rapid sequences of
instabilities, grouped into self-similar, aging avalanches. Crucially, the
quiescent dwell times between avalanches grow in proportion to the system's
age, due to a slow increase of the lowest effective energy barrier. This
slow-down leads to an overall logarithmic aging process.Comment: 7 pages, 3 figure
Topological Pumping over a Photonic Fibonacci Quasicrystal
Quasiperiodic lattices have recently been shown to be a non-trivial
topological phase of matter. Charge pumping -- one of the hallmarks of
topological states of matter -- was recently realized for photons in a
one-dimensional (1D) off-diagonal Harper model implemented in a photonic
waveguide array. The topologically nontrivial 1D Fibonacci quasicrystal (QC) is
expected to facilitate a similar phenomenon, but its discrete nature and lack
of pumping parameter hinder the experimental study of such topological effects.
In this work we overcome these obstacles by utilizing a family of topologically
equivalent QCs which ranges from the Fibonacci QC to the Harper model.
Implemented in photonic waveguide arrays, we observe the topological properties
of this family, and perform a topological pumping of photons across a Fibonacci
QC.Comment: 5 pages, 4 figures, comments are welcom
Bloch oscillations of Path-Entangled Photons
We show that when photons in N-particle path entangled |N,0> + |0,N> state
undergo Bloch oscillations, they exhibit a periodic transition between
spatially bunched and antibunched states. The transition occurs even when the
photons are well separated in space. We study the scaling of the
bunching-antibunching period, and show it is proportional to 1/N.Comment: An error in figure 1b of the original manuscript was corrected, and
the period was redefine
Quantum Walk of Two Interacting Bosons
We study the effect of interactions on the bosonic two-particle quantum walk
and its corresponding spatial correlations. The combined effect of interactions
and Hanbury-Brown Twiss interference results in unique spatial correlations
which depend on the strength of the interaction, but not on its sign. The
results are explained in light of the two-particle spectrum and the physics of
attractively and repulsively bound pairs. We experimentally measure the weak
interaction limit of these effects in nonlinear photonic lattices. Finally, we
discuss an experimental approach to observe the strong interaction limit using
single atoms in optical lattices.Comment: 4 pages, 5 figures. Comments wellcom