Speeding up thermalisation via open quantum system variational optimisation

Optimising open quantum system evolution is an important step on the way to achieving quantum computing and quantum thermodynamic tasks. In this article, we approach optimisation via variational principles and derive an open quantum system variational algorithm explicitly for Lindblad evolution in Liouville space. As an example of such control over open system evolution, we control the thermalisation of a qubit attached to a thermal Lindbladian bath with a damping rate γ. Since thermalisation is an asymptotic process and the variational algorithm we consider is for fixed time, we present a way to discuss the potential speedup of thermalisation that can be expected from such variational algorithms.     

Preparative high-performance liquid chromatographic separation of naphthodianthrones from St. John's Wort

St. John's Wort (Hypericum perforatum), a perennial flowering plant, has been used medicinally for thousands of years and has most recently been identified as an effective treatment for mild to moderate depression and neuralgic disorders. This work presents a procedure for the isolation of naphthodianthrones from St. John's Wort by an accelerated extraction and separation of marker compounds by preparative high-performance liquid chromatography (HPLC) with photodiode array detection. The accelerated extraction method minimizes the extraction time and increases the yield, and the marker compounds obtained by preparative HPLC are of 98% purity. The compounds are characterized by liquid chromatography-mass spectrometry (electrospray ionization) and NMR spectra.     

Two-color photoionization spectroscopy of uranium in a U–Ne hollow cathode discharge tube

A U–Ne hollow cathode discharge tube is used as a source of uranium atomic vapors as well as a photoelectron/photoion detector for carrying out two-color three-photon photoionization spectroscopy of uranium. Using the uranium excitation transition 0 cm⁻¹ (⁵L ₆ ⁰ ) → 16 900.38 cm⁻¹ (⁷M₇) at 591.5-nm laser wavelength as a first step transition and scanning the wavelength of a second laser from 558 to 568 nm, high-lying odd-parity atomic levels of uranium are studied in the energy region 34 500–34 813 cm⁻¹. All the expected 21 odd-parity atomic levels identified by various researchers in this region are observed in a single spectrum, demonstrating the high sensitivity achieved therein. In addition to this, we have identified eight autoionization resonances of uranium starting from its odd-parity atomic level at 33 801.06 cm⁻¹ pumped by two-photon excitation. Four out of these eight autoionization resonances are observed for the first time.     

Selective identification of specific aptamers for the detection of non-typhoidal salmonellosis in an apta-impedimetric sensing format

Microchimica Acta - The authors report on an aptamer-based method for the detection of S. Typhimurium. The aptamers were identified by using a modified cell-based SELEX method (cell-SELEX) by...     

Effect of Nd3+ concentration on CW and pulsed performance of fiber-coupled diode laser pumped Nd:YVO4 laser at 1064 nm

The effect of Nd³⁺ concentration on the CW and Q-switched laser performances at 1064 nm from Nd: YVO₄ has been studied under diode laser pumping in identical laser configuration. The Nd³⁺ concentrations used were 1, 2 and 3 at.% in YVO₄ crystals. Under the CW operations we have compared the thermal lensing effect, slope efficiencies and also the beam quality at the fourth-order degeneracy configuration. Q-switching was done with the help of an acousto-optic modulator and we have compared the pulses obtained from Nd: YVO₄ laser with different doping concentration. It was found that the 1 at.%-doped crystal is the best, offering highest optical-to-optical conversion efficiency (55%), lowest fractional heat load (24%), highest pulse energy (80 μJ) and shortest pulse width (20 ns). It was also found that there was not much difference in performances for 2 and 3 at.%-doped crystals both in CW and Q-switched configurations.     

Computing the link center of a simple polygon

The link center of a simple polygonP is the set of pointsx insideP at which the maximal link-distance fromx to any other point inP is minimized. Here the link distance between two pointsx, y insideP is defined to be the smallest number of straight edges in a polygonal path insideP connectingx toy. We prove several geometric properties of the link center and present an algorithm that calculates this set in timeO(n ²), wheren is the number of sides ofP. We also give anO(n logn) algorithm for finding an approximate link center, that is, a pointx such that the maximal link distance fromx to any point inP is at most one more than the value attained from the true link center.Work on this paper by the second author has been supported by National Science Foundation Grant DMS-8501947. Work by the third author has been supported by the Canadian National Science and Engineering Research Council, Grant A0332. Work by the fifth author has been supported by Office of Naval Research Grant N00014-82-K-0381, National Science Foundation Grant DCR-83-20085, and by grants from the Digital Equipment Corporation, and the IBM Corporation. Work by the seventh author has been supported by a Killam Senior Research Fellowship from the Canada Council, and work by the ninth author has been supported by the National Science Foundation Grants DCR-84-01898 and DCR-84-01633. Part of the work on this paper has been carried out at the Workshop on Movable Separability of Sets at the Bellairs Research Institute of McGill University, Barbados, February 1986. Further acknowledgments can be obtained from the tenth author upon request.     

A technique for on-line sensitivity analysis of flexible manufacturing systems

The recent perturbation analysis approach to discrete event systems is applied to flexible manufacturing systems (FMS). While analytic (queueing) models are useful in preliminary design of such systems, they are not accurate enough at the detailed design/operation stage. Thus, experimentation on detailed simulations or on the actual system has been the way to optimize system performance. Perturbation analysis allows us to derive the sensitivity of system performance, with respect to several design/operating parameters, by observing a single experiment (and without having to actually alter the parameters — often a costly operation). Thus, observation of one experiment can give accurate directions for the improvement of several parameter values. Here we give a simulation example illustrating how perturbation analysis could be used on-line on an FMS to improve its performance, including reducing its operating cost. Experimental results are also presented validating the estimates obtained from this technique.Work supported by U.S. Office of Naval Research Contracts N00014-75-C-0648 and N00014-79-C-0776, and NSF Grant ENG78-15231, at Harvard University.A preliminary version of this paper appeared in the Proc. 1st ORSA/TIMS Conf. on Flexible Manufacturing Systems, August 1984. This version includes two appendices, which relate to implementation of the technique described in the main body of the paper.