4,853 research outputs found
Anderson localization of entangled photons in an integrated quantum walk
Waves fail to propagate in random media. First predicted for quantum
particles in the presence of a disordered potential, Anderson localization has
been observed also in classical acoustics, electromagnetism and optics. Here,
for the first time, we report the observation of Anderson localization of pairs
of entangled photons in a two-particle discrete quantum walk affected by
position dependent disorder. A quantum walk on a disordered lattice is realized
by an integrated array of interferometers fabricated in glass by femtosecond
laser writing. A novel technique is used to introduce a controlled phase shift
into each unit mesh of the network. Polarization entanglement is exploited to
simulate the different symmetries of the two-walker system. We are thus able to
experimentally investigate the genuine effect of (bosonic and fermionic)
statistics in the absence of interaction between the particles. We will show
how different types of randomness and the symmetry of the wave-function affect
the localization of the entangled walkers.Comment: 7 pages, 5 figures, revised version published on Nature Photonics 7,
322-328 (2013
Two bosonic quantum walkers in one-dimensional optical lattices
Dynamical properties of two bosonic quantum walkers in a one-dimensional
lattice are studied theoretically. Depending on the initial state,
interactions, lattice tilting, and lattice disorder, whole plethora of
different behaviors are observed. Particularly, it is shown that two bosons
system manifests the many-body localization like behavior in the presence of a
quenched disorder. The whole analysis is based on a specific decomposition of
the temporal density profile into different contributions from singly and
doubly occupied sites. In this way, the role of interactions is extracted.
Since the contributions can be directly measured in experiments with ultra-cold
atoms in optical lattices, the predictions presented may have some importance
for upcoming experiment.Comment: upgraded reference
Quantum simulation of bosonic-fermionic non-interacting particles in disordered systems via quantum walk
We report on the theoretical analysis of bosonic and fermionic
non-interacting systems in a discrete two-particle quantum walk affected by
different kinds of disorder. We considered up to 100-step QWs with a spatial,
temporal and space-temporal disorder observing how the randomness and the
wavefunction symmetry non-trivially affect the final spatial probability
distribution, the transport properties and the Shannon entropy of the walkers.Comment: 13 pages, 10 figures. arXiv admin note: text overlap with
arXiv:1101.2638 by other author
Simulating quantum statistics with entangled photons: a continuous transition from bosons to fermions
In contrast to classical physics, quantum mechanics divides particles into
two classes-bosons and fermions-whose exchange statistics dictate the dynamics
of systems at a fundamental level. In two dimensions quasi-particles known as
'anyons' exhibit fractional exchange statistics intermediate between these two
classes. The ability to simulate and observe behaviour associated to
fundamentally different quantum particles is important for simulating complex
quantum systems. Here we use the symmetry and quantum correlations of entangled
photons subjected to multiple copies of a quantum process to directly simulate
quantum interference of fermions, bosons and a continuum of fractional
behaviour exhibited by anyons. We observe an average similarity of 93.6\pm0.2%
between an ideal model and experimental observation. The approach generalises
to an arbitrary number of particles and is independent of the statistics of the
particles used, indicating application with other quantum systems and large
scale application.Comment: 10 pages, 5 figure
Universal computation by multi-particle quantum walk
A quantum walk is a time-homogeneous quantum-mechanical process on a graph
defined by analogy to classical random walk. The quantum walker is a particle
that moves from a given vertex to adjacent vertices in quantum superposition.
Here we consider a generalization of quantum walk to systems with more than one
walker. A continuous-time multi-particle quantum walk is generated by a
time-independent Hamiltonian with a term corresponding to a single-particle
quantum walk for each particle, along with an interaction term. Multi-particle
quantum walk includes a broad class of interacting many-body systems such as
the Bose-Hubbard model and systems of fermions or distinguishable particles
with nearest-neighbor interactions. We show that multi-particle quantum walk is
capable of universal quantum computation. Since it is also possible to
efficiently simulate a multi-particle quantum walk of the type we consider
using a universal quantum computer, this model exactly captures the power of
quantum computation. In principle our construction could be used as an
architecture for building a scalable quantum computer with no need for
time-dependent control
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