Higher order traps for some strongly degenerate quantum control systems

Quantum control is necessary for a variety of modern quantum technologies as it allows to optimally manipulate quantum systems. An important problem in quantum control is to establish whether the control objective functional has trapping behaviour or no, namely if it has or no traps -- controls from which it is difficult to escape by local search optimization methods. Higher order traps were previously introduced in [A. N. Pechen, D. J. Tannor, "Are there traps in quantum control landscapes?", Phys. Rev. Lett., 106 (2011), 120402], where 3-rd order traps were found. In this note we show that traps of arbitrarily high order exist for controllable quantum systems with special symmetry in the Hamiltonian.Comment: 4 pages, final versio

On the detailed structure of quantum control landscape for fast single qubit phase-shift gate generation

In this work, we study the detailed structure of quantum control landscape for the problem of single-qubit phase shift gate generation on the fast time scale. In previous works, the absence of traps for this problem was proven on various time scales. A special critical point which was known to exist in quantum control landscapes was shown to be either a saddle or a global extremum, depending on the parameters of the control system. However, in the case of saddle the numbers of negative and positive eigenvalues of Hessian at this point and their magnitudes have not been studied. At the same time, these numbers and magnitudes determine the relative ease or difficulty for practical optimization in a vicinity of the critical point. In this work, we compute the numbers of negative and positive eigenvalues of Hessian at this saddle point and moreover, give estimates on magnitude of these eigenvalues. We also significantly simplify our previous proof of the theorem about this saddle point of the Hessian [Theorem~3 in B.O.~Volkov, O.V.~Morzhin, A.N.~Pechen, J.~Phys.~A: Math. Theor. {\bf 54}, 215303 (2021)].Comment: 12 pages, 2 figures, final versio

Evaluating Application of Knowledge and Skills: The Use of Consensus Expert Review to Assess Conference Abstracts of Field Epidemiology Training Participants

Background: Often evaluations of training programs are limited — with many focusing on the aspects that are easy to measure (e.g., reaction of trainees) without addressing the important outcomes of training, such as how trainees applied their new knowledge, skills, and attitudes. Numerous evaluations fail to measure training’s effect on job performance because few effective methods are available to do so. Particularly difficult is the problem of evaluating multisite training programs that vary considerably in structure and implementation from one site to another. Purpose: NA Setting: NA  Intervention: NA Research Design: We devised a method of a consensus expert review to evaluate the quality of conference abstracts submitted by participants in Field Epidemiology Training Programs – an approach that can provide useful information on how well trainees apply knowledge and skills gained in training, complementing data obtained from other sources and methods. This method is practical, minimally intrusive, and resource-efficient, and it may prove useful for evaluation practice in diverse fields that require training. Data Collection and Analysis: NA Findings: NA