Identification of single-input–single-output quantum linear systems

The purpose of this paper is to investigate system identification for single-input–single-output general (active or passive) quantum linear systems. For a given input we address the following questions: (1) Which parameters can be identified by measuring the output? (2) How can we construct a system realization from sufficient input-output data? We show that for time-dependent inputs, the systems which cannot be distinguished are related by symplectic transformations acting on the space of system modes. This complements a previous result of Guţă and Yamamoto [IEEE Trans. Autom. Control 61, 921 (2016)] for passive linear systems. In the regime of stationary quantum noise input, the output is completely determined by the power spectrum. We define the notion of global minimality for a given power spectrum, and characterize globally minimal systems as those with a fully mixed stationary state. We show that in the case of systems with a cascade realization, the power spectrum completely fixes the transfer function, so the system can be identified up to a symplectic transformation. We give a method for constructing a globally minimal subsystem direct from the power spectrum. Restricting to passive systems the analysis simplifies so that identifiability may be completely understood from the eigenvalues of a particular system matrix

The Quantum Theory of MIMO Markovian Feedback with Diffusive Measurements

Feedback control engineers have been interested in MIMO (multiple-input multiple-output) extensions of SISO (single-input single-output) results of various kinds due to its rich mathematical structure and practical applications. An outstanding problem in quantum feedback control is the extension of the SISO theory of Markovian feedback by Wiseman and Milburn [Phys. Rev. Lett. {\bf 70}, 548 (1993)] to multiple inputs and multiple outputs. Here we generalize the SISO homodyne-mediated feedback theory to allow for multiple inputs, multiple outputs, and \emph{arbitrary} diffusive quantum measurements. We thus obtain a MIMO framework which resembles the SISO theory and whose additional mathematical structure is highlighted by the extensive use of vector-operator algebra.Comment: 17 pages, 2 figure

Major and minor fisheries harbours of India. 8. Fisherries harbours along the coasts of North Andhra Pradesh, Orissa and West Bengal

The present account gives information about the three major and five minor fisheries harbours along the coasts of north Andhra Pradesh, Orissa and West Benga

Stock assessment of tunas from the Indian seas

The tuna catch in India in the small scale sector fluctuated between 23 170 tonnes and 35 610 tonnes during 1984-88, the average catch for the priod being 29 146 tonnes. In 1989, 45,240 tonnes of tunas were landed by the artisanal sector

The tribological performance of ultra-hard ceramic composite coatings obtained through microarc oxidation

A dense ceramic oxide coating approximately 100 μm thick was prepared on a 7075 Al alloy by microarc oxidation in an alkali-silicate electrolytic solution. Coating thickness and surface roughness (Ra) were measured during coating formation. The influence of current density, electrolyte temperature and inter-electrode distance on coating kinetics was investigated. Microstructure and phase compositions were analysed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The microhardness of the coating was also measured. The tribological performance of the coatings was evaluated using a dry sand abrasion test, a solid particle erosion test and a pin-on-disc sliding wear test. In addition, the results are compared to detonation-sprayed alumina (Al2O3) coating and bulk Al2O3. The basic mechanism of microarc coating formation is explained. The material removal mechanism during solid particle erosion was investigated, and structure-property correlations were established