14 research outputs found
Photon number conservation and photon interference
The group theoretical aspect of the description of passive lossless optical
four-ports (beam splitters) is revisited. It is shown through an example, that
this approach can be useful in understanding interferometric schemes where a
low number of photons interfere. The formalism is extended to passive lossless
optical six-ports, their SU(3)-theory is outlined.Comment: Contribution at "Classical and Quantum Interference" workshop in RCO,
Olomouc, Oct. 25-26 2001. A corrected versio
Optimization of periodic single-photon sources based on combined multiplexing
We consider periodic single-photon sources with combined multiplexing in
which the outputs of several time-multiplexed sources are spatially
multiplexed. We give a full statistical description of such systems in order to
optimize them with respect to maximal single-photon probability. We carry out
the optimization for a particular scenario which can be realized in bulk optics
and its expected performance is potentially the best at the present state of
the art. We find that combined multiplexing outperforms purely spatially or
time multiplexed sources for certain parameters only, and we characterize these
cases. Combined multiplexing can have the advantages of possibly using less
nonlinear sources, achieving higher repetition rates, and the potential
applicability for continuous pumping. We estimate an achievable single-photon
probability between 85% and 89%.Comment: 11 pages, 6 figur
Optimization of periodic single-photon sources
We introduce a theoretical framework which is suitable for the description of
all spatial and time-multiplexed periodic single-photon sources realized or
proposed thus far. Our model takes into account all possibly relevant loss
mechanisms. This statistical analysis of the known schemes shows that
multiplexing systems can be optimized in order to produce maximal single-photon
probability for various sets of loss parameters by the appropriate choice of
the number of multiplexed units of spatial multiplexers or multiplexed time
intervals and the input mean photon pair number, and reveals the physical
reasons of the existence of the optimum. We propose a novel time-multiplexed
scheme to be realized in bulk optics, which, according to the present analysis,
would have promising performance when experimentally realized. It could provide
a single-photon probability of 85\% with a choice of experimental parameters
which are feasible according to the experiments known from the literature.Comment: 13 pages, 18 figure
Single-photon sources based on asymmetric spatial multiplexing with optimized inputs
We develop a statistical theory describing the operation of multiplexed single-photon sources equipped with photon-number-resolving detectors that includes the potential use of different input mean photon numbers in each of the multiplexed units. This theory accounts for all relevant loss mechanisms and allows for the maximization of the single-photon probabilities under realistic conditions by optimizing the different input mean photon numbers unit-wise and the detection strategy that can be defined in terms of actual detected photon numbers. We apply this description to analyze periodic single-photon sources based on asymmetric spatial multiplexing realized with general asymmetric routers. We show that optimizing the different input mean photon numbers results in maximal single-photon probabilities higher than those achieved by using optimal identical input mean photon numbers in this setup. We identify the parameter ranges of the system for which the enhancement in the single-photon probability for the various detection strategies is relevant. An additional advantage of the unit-wise optimization of the input mean photon numbers is that it can result in the decrease of the optimal system size needed to maximize the single-photon probability. We find that the highest single-photon probability that our scheme can achieve in principle when realized with state-of-the-art bulk optical elements is 0.935. This is the highest one to our knowledge that has been reported thus far in the literature for experimentally realizable single-photon sources
The Column Generatiion and Traiin Crew Scheduliing
Better productivity and efficiency is more and more required in the railway operation. The train crew management is one of the several problems that could be solved using mathematical methods. Crew management is a problem that is well-known in Operations Research. We compare two approaches for solving the train crew scheduling problem. The first approach consists of solving the original problem by single model. The second approach corresponds to the step-by-step column generation. This technique was originally based on Dantzig-Wolfe decomposition. The benchmarks used for comparison of both approaches originate in real problems from railway systems in Slovakia and Hungary
Preconditioning in the Backtracking Duty Generation of Passenger Rail Crew Scheduling: A Case Study
We describe briefly the crew scheduling and rostering approach implemented in Railm@n, the system used by MAV START, the passenger railway transport company of Hungary, to organize the work of passenger train crews that is, conductors. Then we discuss the scheduling (duty generation) phase of the algorithm in detail. When treated in full generality, the problem already scales to an untractable size. We describe our successful experience with the use of preconditioning to keep the problem tractable. The approach may be useful in timetable planning and depot planning, too