The purpose of this paper is to formulate and solve a H ∞ controller synthesis problem for a class of non-commutative linear stochastic systems which includes many examples of interest in quantum technology. The paper includes results on the class of such systems for which the quantum commutation relations are preserved (such a requirement must be satisfied in a physical quantum system). A quantum version of standard (classical) dissipativity results are presented and from this a quantum version of the Strict Bounded Real Lemma is derived. This enables a quantum version of the two Riccati solution to the H ∞ control problem to be presented. This result leads to controllers which may be realized using purely quantum, purely classical or a mixture of quantum and classical elements. This issue of physical realizability of the controller is examined in detail, and necessary and sufficient conditions are given. Our results are constructive in the sense that we provide explicit formulas for the Hamiltonian function and coupling operator corresponding to the controller.
Abstract-This paper considers the problem of robust stability for a class of uncertain quantum systems subject to unknown perturbations in the system Hamiltonian. Some general stability results are given for different classes of perturbations to the system Hamiltonian. Then, the special case of a nominal linear quantum system is considered with either quadratic or nonquadratic perturbations to the system Hamiltonian. In this case, robust stability conditions are given in terms of strict bounded real conditions.
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AbstractPurpose -The purpose of this paper is to determine what factors contributed to three universities achieving environmental sustainability. Design/methodology/approach -A case study methodology was used to determine how each factor contributed to the institutions' sustainability. Site visits, fieldwork, document reviews, and interviews with administration, faculty, staff, and students from the participating institutions were employed as primary data collection strategies. Findings -The six factors identified in the literature as contributing to environmental sustainability were present at all three institutions: green campus operation measures; campus administration, organization, and leadership; teaching, research, and service; campus-wide actions and activities; institutional assessment of campus sustainability measures; and established methods for overcoming barriers.Research limitations/implications -This study was delimited to the six factors that were identified in the literature and the three institutions that participated in this study. The research will add to the literature on creating sustainable campuses and will also provide a foundation for further study on the progress and impact of campus sustainability efforts. Originality/value -A number of individual case studies have described what certain institutions have done. A smaller number of case studies have identified what factors have contributed to certain institutions' achieved environmental sustainability.
This paper considers a Popov type approach to the problem of robust stability for a class of uncertain linear quantum systems subject to unknown perturbations in the system Hamiltonian. A general stability result is given for a general class of perturbations to the system Hamiltonian. Then, the special case of a nominal linear quantum system is considered with quadratic perturbations to the system Hamiltonian. In this case, a robust stability condition is given in terms of a frequency domain condition which is of the same form as the standard Popov stability condition.
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