50,088 research outputs found
Frequency Multiplexing for Quasi-Deterministic Heralded Single-Photon Sources
Single-photon sources based on optical parametric processes have been used
extensively for quantum information applications due to their flexibility,
room-temperature operation and potential for photonic integration. However, the
intrinsically probabilistic nature of these sources is a major limitation for
realizing large-scale quantum networks. Active feedforward switching of photons
from multiple probabilistic sources is a promising approach that can be used to
build a deterministic source. However, previous implementations of this
approach that utilize spatial and/or temporal multiplexing suffer from rapidly
increasing switching losses when scaled to a large number of modes. Here, we
break this limitation via frequency multiplexing in which the switching losses
remain fixed irrespective of the number of modes. We use the third-order
nonlinear process of Bragg scattering four-wave mixing as an efficient
ultra-low noise frequency switch and demonstrate multiplexing of three
frequency modes. We achieve a record generation rate of
multiplexed photons per second with an ultra-low = 0.07, indicating
high single-photon purity. Our scalable, all-fiber multiplexing system has a
total loss of just 1.3 dB independent of the number of multiplexed modes, such
that the 4.8 dB enhancement from multiplexing three frequency modes markedly
overcomes switching loss. Our approach offers a highly promising path to
creating a deterministic photon source that can be integrated on a chip-based
platform.Comment: 28 pages, 9 figures. Comments welcom
Fast recursive filters for simulating nonlinear dynamic systems
A fast and accurate computational scheme for simulating nonlinear dynamic
systems is presented. The scheme assumes that the system can be represented by
a combination of components of only two different types: first-order low-pass
filters and static nonlinearities. The parameters of these filters and
nonlinearities may depend on system variables, and the topology of the system
may be complex, including feedback. Several examples taken from neuroscience
are given: phototransduction, photopigment bleaching, and spike generation
according to the Hodgkin-Huxley equations. The scheme uses two slightly
different forms of autoregressive filters, with an implicit delay of zero for
feedforward control and an implicit delay of half a sample distance for
feedback control. On a fairly complex model of the macaque retinal horizontal
cell it computes, for a given level of accuracy, 1-2 orders of magnitude faster
than 4th-order Runge-Kutta. The computational scheme has minimal memory
requirements, and is also suited for computation on a stream processor, such as
a GPU (Graphical Processing Unit).Comment: 20 pages, 8 figures, 1 table. A comparison with 4th-order Runge-Kutta
integration shows that the new algorithm is 1-2 orders of magnitude faster.
The paper is in press now at Neural Computatio
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