1,822 research outputs found
Heralding two- and four-photon path entanglement on chip
Generating quantum entanglement is not only an important scientific endeavor,
but will be essential to realizing quantum-enhanced technologies, in
particular, quantum-enhanced measurements with precision beyond classical
limits. We investigate the heralded generation of multiphoton entanglement for
quantum metrology using a reconfigurable integrated waveguide device in which
projective measurement of auxiliary photons heralds the generation of
path-entangled states. We use four and six-photon inputs, to analyze the
heralding process of two- and four-photon NOON states-a superposition of N
photons in two paths, capable of enabling phase supersensitive measurements at
the Heisenberg limit. Realistic devices will include imperfections; as part of
the heralded state preparation, we demonstrate phase superresolution within our
chip with a state that is more robust to photon loss
Optimizing a basket against the efficient market hypothesis
[No abstract available
Dual impressions in Coriolanus
The moral tone of Shakespeare\u27s Coriolanus is disturbingly ambivalent. At one and the same time in numerous scenes and incidents Shakespeare presents dual opposing impressions of the protangonist and his society
Emergence of chaotic behaviour in linearly stable systems
Strong nonlinear effects combined with diffusive coupling may give rise to
unpredictable evolution in spatially extended deterministic dynamical systems
even in the presence of a fully negative spectrum of Lyapunov exponents. This
regime, denoted as ``stable chaos'', has been so far mainly characterized by
numerical studies. In this manuscript we investigate the mechanisms that are at
the basis of this form of unpredictable evolution generated by a nonlinear
information flow through the boundaries. In order to clarify how linear
stability can coexist with nonlinear instability, we construct a suitable
stochastic model. In the absence of spatial coupling, the model does not reveal
the existence of any self-sustained chaotic phase. Nevertheless, already this
simple regime reveals peculiar differences between the behaviour of finite-size
and that of infinitesimal perturbations. A mean-field analysis of the truly
spatially extended case clarifies that the onset of chaotic behaviour can be
traced back to the diffusion process that tends to shift the growth rate of
finite perturbations from the quenched to the annealed average. The possible
characterization of the transition as the onset of directed percolation is also
briefly discussed as well as the connections with a synchronization transition.Comment: 30 pages, 8 figures, Submitted to Journal of Physics
Shor's quantum factoring algorithm on a photonic chip
Shor's quantum factoring algorithm finds the prime factors of a large number
exponentially faster than any other known method a task that lies at the heart
of modern information security, particularly on the internet. This algorithm
requires a quantum computer a device which harnesses the `massive parallelism'
afforded by quantum superposition and entanglement of quantum bits (or qubits).
We report the demonstration of a compiled version of Shor's algorithm on an
integrated waveguide silica-on-silicon chip that guides four single-photon
qubits through the computation to factor 15.Comment: 2 pages, 1 figur
Nonmonotonic roughness evolution in unstable growth
The roughness of vapor-deposited thin films can display a nonmonotonic
dependence on film thickness, if the smoothening of the small-scale features of
the substrate dominates over growth-induced roughening in the early stage of
evolution. We present a detailed analysis of this phenomenon in the framework
of the continuum theory of unstable homoepitaxy. Using the spherical
approximation of phase ordering kinetics, the effect of nonlinearities and
noise can be treated explicitly. The substrate roughness is characterized by
the dimensionless parameter , where denotes the
roughness amplitude, is the small scale cutoff wavenumber of the
roughness spectrum, and is the lattice constant. Depending on , the
diffusion length and the Ehrlich-Schwoebel length , five regimes
are identified in which the position of the roughness minimum is determined by
different physical mechanisms. The analytic estimates are compared by numerical
simulations of the full nonlinear evolution equation.Comment: 16 pages, 6 figures, to appear on Phys. Rev.
Dynamic model of fiber bundles
A realistic continuous-time dynamics for fiber bundles is introduced and
studied both analytically and numerically. The equation of motion reproduces
known stationary-state results in the deterministic limit while the system
under non-vanishing stress always breaks down in the presence of noise.
Revealed in particular is the characteristic time evolution that the system
tends to resist the stress for considerable time, followed by sudden complete
rupture. The critical stress beyond which the complete rupture emerges is also
obtained
Characterizing dynamics with covariant Lyapunov vectors
A general method to determine covariant Lyapunov vectors in both discrete-
and continuous-time dynamical systems is introduced. This allows to address
fundamental questions such as the degree of hyperbolicity, which can be
quantified in terms of the transversality of these intrinsic vectors. For
spatially extended systems, the covariant Lyapunov vectors have localization
properties and spatial Fourier spectra qualitatively different from those
composing the orthonormalized basis obtained in the standard procedure used to
calculate the Lyapunov exponents.Comment: 4 pages, 3 figures, submitted to Physical Review letter
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