1,185 research outputs found
Quantum walk on distinguishable non-interacting many-particles and indistinguishable two-particle
We present an investigation of many-particle quantum walks in systems of
non-interacting distinguishable particles. Along with a redistribution of the
many-particle density profile we show that the collective evolution of the
many-particle system resembles the single-particle quantum walk evolution when
the number of steps is greater than the number of particles in the system. For
non-uniform initial states we show that the quantum walks can be effectively
used to separate the basis states of the particle in position space and
grouping like state together. We also discuss a two-particle quantum walk on a
two- dimensional lattice and demonstrate an evolution leading to the
localization of both particles at the center of the lattice. Finally we discuss
the outcome of a quantum walk of two indistinguishable particles interacting at
some point during the evolution.Comment: 8 pages, 7 figures, To appear in special issue: "quantum walks" to be
published in Quantum Information Processin
Directional correlations in quantum walks with two particles
Quantum walks on a line with a single particle possess a classical analogue. Involving more walkers opens up the possibility of studying collective quantum effects, such as many-particle correlations. In this context, entangled initial states and the indistinguishability of the particles play a role. We consider the directional correlations between two particles performing a quantum walk on a line. For non-interacting particles, we find analytic asymptotic expressions and give the limits of directional correlations. We show that by introducing delta-interaction between the particles, one can exceed the limits for non-interacting particles
The Hong-Ou-Mandel effect with atoms
Controlling light at the level of individual photons has led to advances in
fields ranging from quantum information and precision sensing to fundamental
tests of quantum mechanics. A central development that followed the advent of
single photon sources was the observation of the Hong-Ou- Mandel (HOM) effect,
a novel two-photon path interference phenomenon experienced by
indistinguishable photons. The effect is now a central technique in the field
of quantum optics, harnessed for a variety of applications such as diagnosing
single photon sources and creating probabilistic entanglement in linear quantum
computing. Recently, several distinct experiments using atomic sources have
realized the requisite control to observe and exploit Hong-Ou-Mandel
interference of atoms. This article provides a summary of this phenomenon and
discusses some of its implications for atomic systems. Transitioning from the
domain of photons to atoms opens new perspectives on fundamental concepts, such
as the classification of entanglement of identical particles. It aids in the
design of novel probes of quantities such as entanglement entropy by combining
well established tools of AMO physics - unity single-atom detection, tunable
interactions, and scalability - with the Hong-Ou-Mandel interference.
Furthermore, it is now possible for established protocols in the photon
community, such as measurement-induced entanglement, to be employed in atomic
experiments that possess deterministic single-particle production and
detection. Hence, the realization of the HOM effect with atoms represents a
productive union of central ideas in quantum control of atoms and photons.Comment: 19 pages, 7 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
Counting Statistics of Many-Particle Quantum Walks
We study quantum walks of many non-interacting particles on a beam splitter
array, as a paradigmatic testing ground for the competition of single- and
many-particle interference in a multi-mode system. We derive a general
expression for multi-mode particle-number correlation functions, valid for
bosons and fermions, and infer pronounced signatures of many-particle
interferences in the counting statistics.Comment: 4 pages, 4 figure
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