9,667 research outputs found
Entangling spins by measuring charge: a parity-gate toolbox
The parity gate emerged recently as a promising resource for performing
universal quantum computation with fermions using only linear interactions.
Here we analyse the parity gate (P-gate) from a theoretical point of view in
the context of quantum networks. We present several schemes for entanglement
generation with P-gates and show that native networks simplify considerably the
resources required for producing multi-qubit entanglement, like n-GHZ states.
Other applications include a Bell-state analyser and teleportation. We also
show that cluster state fusion can be performed deterministically with parity
measurements. We then extend this analysis to hybrid quantum networks
containing spin and mode qubits. Starting from an easy-to-prepare resource
(spin-mode entanglement of single electrons) we show how to produce a spin
n-GHZ state with linear elements (beam-splitters and local spin-flips) and
charge-parity detectors; this state can be used as a resource in a spin quantum
computer or as a precursor for constructing cluster states. Finally, we
construct a novel spin CZ-gate by using the mode degrees of freedom as
ancillae.Comment: updated to the published versio
Reconfigurable photonic RF filter based on opto-VLSI processing
In this paper, a novel reconfigurable 5-tap photonic RF filter based on Opto-VLSI processor is proposed where an Opto-VLSI processor is used in conjunction with a 5-fibre Bragg grating (FBG) array to slice the spectrum of a broad band light source, thus achieving commensurate true-time delays and variable tap weights. The proposed photonic RF filterstructure is experimentally demonstrated by means of several examples which show the capability of the Opto-VLSI processor to synthesise transversal RF filter responses with adaptive weights
The design of a neural network compiler
Computer simulation is a flexible and economical way for
rapid prototyping and concept evaluation with Neural
Network (NN) models. Increasing research on NNs has led
to the development of several simulation programs. Not
all simulations have the same scope. Some simulations
allow only a fixed network model and some are more
general. Designing a simulation program for general
purpose NN models has become a current trend nowadays
because of its flexibility and efficiency. A proper
programming language specifically for NN models is
preferred since the existing high-level languages such as
C are for NN designers from a strong computer background.
The program translations for NN languages come from
combinations which are either interpreter and/or
compiler. There are also various styles of programming
languages such as a procedural, functional, descriptive
and object-oriented.
The main focus of this thesis is to study the
feasibility of using a compiler method for the
development of a general-purpose simulator - NEUCOMP that
compiles the program written as a list of mathematical
specifications of the particular NN model and translates
it into a chosen target program. The language supported
by NEUCOMP is based on a procedural style. Information
regarding the list of mathematical statements required by
the NN models are written in the program. The
mathematical statements used are represented by scalar,
vector and matrix assignments. NEUCOMP translates these
expressions into actual program loops.
NEUCOMP enables compilation of a simulation program
written in the NEUCOMP language for any NN model,
contains graphical facilities such as portraying the NN
architecture and displaying a graph of the result during
training and finally to have a program that can run on a
parallel shared memory multi-processor system
Opto-VLSI-based adaptive optical power splitter/combiner for next generation dynamic optical telecommunication networks
The demand for optical power splitters is growing globally, due to the rapid deployment of fibre-to-the-premises, optical metropolitan area network (MAN), and active optical cables for TV/Video signal transport. Optical splitters play an important role in passive optical network (PON) technology by enabling several hundred users to share one optical line terminal. However, current PONs, which use fixed optical power splitters, have limited reconfigurability particularly in adding/dropping users to/from an optical network unit.
An adaptive optical power splitter (OPS) can dynamically reallocate the opticalpower in the entire network according to the real-time distribution of users and services, thus providing numerous advantages such as improve an optical network efficiency, scalability, and reliability. An adaptive OPS is also important for realizing self-healing ring-to-ring optical MAN, thus offering automatic communication recovery when line break occurs. In addition, future optical line protection systems will require adaptive optical splitters to switch optical signals from faulty lines to active power lines, avoid the use of optical attenuators and/or amplifiers, and achieve real time line monitoring. An adaptive OPS can also be incorporated in tunable optical dispersion compensators, optical attenuator and optical gain equalizer, and reconfigurable optical switches.
This thesis proposes and demonstrates the principle of a novel Opto-VLSI-based adaptive optical splitter/combiner for next generation dynamic optical telecommunication networks. The proposed splitter structure enables an input optical power to be split adaptively into a larger number of output fibre ports, through optimized phase holograms driving the Opto-VLSI processor. The new adaptive optical splitter has additional advantages including lossless operation, adequate inter-port crosstalk, compressed hardware and simple user interface.
This thesis demonstrates, in particular, the concept of an adaptive optical power splitter employing an Opto-VLSI processor and a 4-f imaging system experimentally in three stages as follow: (i) a 1×2 adaptive optical power splitter based on an Opto-VLSI processor, a fibre collimator array and 4-f imaging systems (single lens), (ii) a 1×4 adaptive optical power splitter based on an Opto-VLSI processor, a fibre array and 4-f imaging systems (single lens), and (iii) a 1×N lossless adaptive optical power splitter structure integrating an Opto-VLSI processor, optical amplifiers, a fibre array, and an array of 4-f imaging systems (lens array). The thesis also demonstrates the concept of an adaptive optical signal combiner which enables multiple signals to be combined with user-defined weight profiles into a single fibre port.
Experimental results demonstrate that an input optical signal can arbitrarily be split into N signals and coupled into optical fibre ports by uploading optimized multicasting phase holograms onto the Opto-VLSI processor. They also demonstrate that N input optical signals can be dynamically combined with arbitrary weights into a single optical fibre port. Excellent agreement between theoretical and experimental results is demonstrated. The total insertion loss of the optical power splitter is only 5 dB. Results also show that the optical amplifiers can compensate for the insertion and splitting losses, thus enabling lossless splitter operation. A crosstalk level around -25 dB and a wavelength spectral range exceeding 40 nm is experimentally realized.
In addition, a novel broadband adaptive RF power splitter/combiner based on Opto-VLSI processor is proposed and experimentally demonstrated. By uploading optimized multicasting phase holograms onto the software-driven Opto-VLSI processor, the input RF signal is dynamically split and directed to different output ports, with userdefined splitting ratios. Also, multiple input RF signals can be dynamically combined with arbitrary user-defined weights. As a proof-of-concept demonstration, two input RF signals are dynamically combined with different user-defined weight profiles.
We also propose and demonstrate a photonic microwave filter based on the use of an Opto-VLSI-based adaptive optical combiner. The experimental results demonstrate that the developed Opto-VLSI-based adaptive optical combiner can dynamically route multiple input optical signals to a single output, with user-defined weight profiles, thus realising a tunable microwave filter.
Overall this Opto-VLSI-based adaptive optical power splitter should allow as many as 32 output ports to be supported while achieving high splitting resolution and dynamic range. This will greatly enhance the efficiency of optical communication networks
Harnessing optical micro-combs for microwave photonics
In the past decade, optical frequency combs generated by high-Q
micro-resonators, or micro-combs, which feature compact device footprints, high
energy efficiency, and high-repetition-rates in broad optical bandwidths, have
led to a revolution in a wide range of fields including metrology, mode-locked
lasers, telecommunications, RF photonics, spectroscopy, sensing, and quantum
optics. Among these, an application that has attracted great interest is the
use of micro-combs for RF photonics, where they offer enhanced functionalities
as well as reduced size and power consumption over other approaches. This
article reviews the recent advances in this emerging field. We provide an
overview of the main achievements that have been obtained to date, and
highlight the strong potential of micro-combs for RF photonics applications. We
also discuss some of the open challenges and limitations that need to be met
for practical applications.Comment: 32 Pages, 13 Figures, 172 Reference
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