Lower Bounds on Quantum Annealing Times

The adiabatic theorem provides sufficient conditions for the time needed to prepare a target ground state. While it is possible to prepare a target state much faster with more general quantum annealing protocols, rigorous results beyond the adiabatic regime are rare. Here, we provide such a result, deriving lower bounds on the time needed to successfully perform quantum annealing. The bounds are asymptotically saturated by three toy models where fast annealing schedules are known: the Roland and Cerf unstructured search model, the Hamming spike problem, and the ferromagnetic p-spin model. Our bounds demonstrate that these schedules have optimal scaling. Our results also show that rapid annealing requires coherent superpositions of energy eigenstates, singling out quantum coherence as a computational resource.Comment: accepted to PR

Simultaneous Stoquasticity

Stoquastic Hamiltonians play a role in the computational complexity of the local Hamiltonian problem as well as the study of classical simulability. In particular, stoquastic Hamiltonians can be straightforwardly simulated using Monte Carlo techniques. We address the question of whether two or more Hamiltonians may be made simultaneously stoquastic via a unitary transformation. This question has important implications for the complexity of simulating quantum annealing where quantum advantage is related to the stoquasticity of the Hamiltonians involved in the anneal. We find that for almost all problems no such unitary exists and show that the problem of determining the existence of such a unitary is equivalent to identifying if there is a solution to a system of polynomial (in)equalities in the matrix elements of the initial and transformed Hamiltonians. Solving such a system of equations is NP-hard. We highlight a geometric understanding of this problem in terms of a collection of generalized Bloch vectors.Comment: 11 pages, 1 figure; (v2) updated to match Physical Review A versio

Falling through the cracks: Gaps and barriers in the mental health system for America's disadvantaged children

The system for providing mental health services to children is fragmented and complex, and children and their families face multiple barriers to accessing care. This is especially true for children in low-income families, who have the greatest rate of mental health disorders but have the highest underutilization of services. The first section of this paper describes the unmet need for children's mental health services, including reasons for the disproportionate need among low-income children. The second section provides a brief overview of the history of children's mental health policies. The third section outlines the types of services available to children, highlighting the problems with this service delivery system. This is followed by a discussion of barriers that families face in accessing care. The paper concludes with recommendations for improving this fragmented system of service delivery.Mental health services Children Poverty

Reduzierung des Energie- und Waschmittelverbrauchs in gewerblichen Waeschereien Zusammenfassender Abschlussbericht

The aim of this research project was to investigate innovations regarding the reduction of energy and detergent consumption in industrial laundries under consideration of the present state of the art with regard to their feasibility. In the case of promising preresults, they were directly converted into new products. These new products were tested with regard to their suitability in practice. Basis for the evaluation were the corresponding test criteria applying according to RAL quality label 992 ''proper linen care'', which define the maintenance of the textile products regarding chemical and mechanical deterioration (chemical deterioration factor and strength reduction), white quality (degree of whiteness, basic white value and colour deviation number) as well as anorganic residues (anorganic encrustation). No damaging to the textile products could be determined. Within the framework of this research project 23 patents were applied for. Depending on the product water, energy and time savings of up to 50% compared with conventional processes are feasible. The lifetime of the textiles was not impaired. The innovative concepts, which were put into practice within the framework of this research project, thus contribute to a sustainable economization. (orig.)SIGLEAvailable from TIB Hannover: F04B1223 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung (BMBF), Bonn (Germany)DEGerman