Control of non-controllable quantum systems: A quantum control algorithm based on Grover iteration

A new notion of controllability, eigenstate controllability, is defined for finite-dimensional bilinear quantum mechanical systems which are neither strongly completely controllably nor completely controllable. And a quantum control algorithm based on Grover iteration is designed to perform a quantum control task of steering a system, which is eigenstate controllable but may not be (strongly) completely controllable, from an arbitrary state to a target state.Comment: 7 pages, no figures, submitte

Experimental Hamiltonian Identification for Qubits subject to Multiple Independent Control Mechanisms

We consider a qubit subject to various independent control mechanisms and present a general strategy to identify both the internal Hamiltonian and the interaction Hamiltonian for each control mechanism, relying only on a single, fixed readout process such as $\sigma_z$ measurements.Comment: submitted to Proceedings of the QCMC04 (4 pages RevTeX, 5 figures

Degrees of controllability for quantum systems and applications to atomic systems

Precise definitions for different degrees of controllability for quantum systems are given, and necessary and sufficient conditions are discussed. The results are applied to determine the degree of controllability for various atomic systems with degenerate energy levels and transition frequencies.Comment: 20 pages, IoP LaTeX, revised and expanded versio

Quantum System Identification by Bayesian Analysis of Noisy Data: Beyond Hamiltonian Tomography

We consider how to characterize the dynamics of a quantum system from a restricted set of initial states and measurements using Bayesian analysis. Previous work has shown that Hamiltonian systems can be well estimated from analysis of noisy data. Here we show how to generalize this approach to systems with moderate dephasing in the eigenbasis of the Hamiltonian. We illustrate the process for a range of three-level quantum systems. The results suggest that the Bayesian estimation of the frequencies and dephasing rates is generally highly accurate and the main source of errors are errors in the reconstructed Hamiltonian basis.Comment: 6 pages, 3 figure

Meeting sexual partners online: associated sexual behaviour and prevalent chlamydia infection among adolescents in Norway: a cross-sectional study

OBJECTIVES: Evidence is mixed as to whether meeting sexual partners online ('internet-partners') is associated with risky sexual behaviour and/or sexually transmitted infection transmission. Accordingly, we sought to estimate the prevalence of reporting various online romantic and sexual activities among Norwegian adolescents, including internet-partners, and the reason for meeting them and to examine differences in sexual behaviour, partnership characteristics and chlamydia infection prevalence among those reporting internet-partners versus those reporting only offline partners. METHODS: Population-based cross-sectional survey among sexually experienced girls and boys, 15-20 years, using electronic questionnaires and collecting urine samples for Chlamydia trachomatis PCR testing (79% provided both, n=1023). We used logistic regression to examine associations, adjusting for potentially confounding variables. RESULTS: Overall, 30% of both genders reported internet-partners (ever). Boys (but not girls) with internet-partners had higher chlamydia prevalence than those reporting meeting sexual partners only offline (8.1%, 95% CI 4.3% to 13.7% vs 1.6%, 0.5% to 3.7%). Two-thirds of girls and 37% of boys reported meeting their most recent internet-partner to start a romantic relationship, while the remainder did so with the specific intention of having sex. Among both genders, reporting sexual (vs romantic) reasons for meeting their most recent internet-partners was associated with reporting several risky sexual behaviours, including multiple recent sex partners (adjusted OR girls: 3.27, boys: 2.48) and three-fold higher chlamydia prevalence. CONCLUSIONS: This population-based study suggests that internet-partners are common among adolescents in Norway, and the reason for meeting them was more strongly associated with additionally reporting sexual risk behaviours and prevalent chlamydia infection than the internet itself as a meeting venue

Clinical and functional characterisation of a novel TNFRSF1A c.605T > A/V173D cleavage site mutation associated with tumour necrosis factor receptor-associated periodic fever syndrome (TRAPS), cardiovascular complications and excellent response to etanercept treatment.

Objectives: To study the clinical outcome, treatment response, T-cell subsets and functional consequences of a novel tumour necrosis factor (TNF) receptor type 1 (TNFRSF1A) mutation affecting the receptor cleavage site. Methods: Patients with symptoms suggestive of tumour necrosis factor receptor-associated periodic syndrome (TRAPS) and 22 healthy controls (HC) were screened for mutations in the TNFRSF1A gene. Soluble TNFRSF1A and inflammatory cytokines were measured by ELISAs. TNFRSF1A shedding was examined by stimulation of peripheral blood mononuclear cells (PBMCs) with phorbol 12-myristate 13-acetate followed by flow cytometric analysis (FACS). Apoptosis of PBMCs was studied by stimulation with TNFa in the presence of cycloheximide and annexin V staining. T cell phenotypes were monitored by FACS. Results: TNFRSF1A sequencing disclosed a novel V173D/ p.Val202Asp substitution encoded by exon 6 in one family, the c.194–14G.A splice variant in another and the R92Q/p.Arg121Gln substitution in two families. Cardiovascular complications (lethal heart attack and peripheral arterial thrombosis) developed in two V173D patients. Subsequent etanercept treatment of the V173D carriers was highly effective over an 18-month follow-up period. Serum TNFRSF1A levels did not differ between TRAPS patients and HC, while TNFRSF1A cleavage from monocytes was significantly reduced in V173D and R92Q patients. TNFa-induced apoptosis of PBMCs and T-cell senescence were comparable between V173D patients and HC. Conclusions: The TNFRSF1A V173D cleavage site mutation may be associated with an increased risk for cardiovascular complications and shows a strong response to etanercept. T-cell senescence does not seem to have a pathogenetic role in affected patients

Optimal Control of One-Qubit Gates

We consider the problem of carrying an initial Bloch vector to a final Bloch vector in a specified amount of time under the action of three control fields (a vector control field). We show that this control problem is solvable and therefore it is possible to optimize the control. We choose the physically motivated criteria of minimum energy spent in the control, minimum magnitude of the rate of change of the control and a combination of both. We find exact analytical solutions.Comment: 5 page

Review of biorthogonal coupled cluster representations for electronic excitation

Single reference coupled-cluster (CC) methods for electronic excitation are based on a biorthogonal representation (bCC) of the (shifted) Hamiltonian in terms of excited CC states, also referred to as correlated excited (CE) states, and an associated set of states biorthogonal to the CE states, the latter being essentially configuration interaction (CI) configurations. The bCC representation generates a non-hermitian secular matrix, the eigenvalues representing excitation energies, while the corresponding spectral intensities are to be derived from both the left and right eigenvectors. Using the perspective of the bCC representation, a systematic and comprehensive analysis of the excited-state CC methods is given, extending and generalizing previous such studies. Here, the essential topics are the truncation error characteristics and the separability properties, the latter being crucial for designing size-consistent approximation schemes. Based on the general order relations for the bCC secular matrix and the (left and right) eigenvector matrices, formulas for the perturbation-theoretical (PT) order of the truncation errors (TEO) are derived for energies, transition moments, and property matrix elements of arbitrary excitation classes and truncation levels. In the analysis of the separability properties of the transition moments, the decisive role of the so-called dual ground state is revealed. Due to the use of CE states the bCC approach can be compared to so-called intermediate state representation (ISR) methods based exclusively on suitably orthonormalized CE states. As the present analysis shows, the bCC approach has decisive advantages over the conventional CI treatment, but also distinctly weaker TEO and separability properties in comparison with a full (and hermitian) ISR method

Hotline update of clinical trials and registries presented at the German Cardiac Society Meeting 2009

This review article gives an overview on a number of novel clinical trials and registries in the field of cardiovascular medicine. Key presentations made at the 75th annual meeting of the German Cardiac Society, held in Mannheim, Germany, in April 2009 are reported. The data were presented by leading experts in the field with relevant positions in the trials and registries. These comprehensive summaries should provide the readers with the most recent data on diagnostic and therapeutic developments in cardiovascular medicine similar as previously reported (Rosenkranz et al. in Clin Res Cardiol 96:457–468, 9; Maier et al. in Clin Res Cardiol 97:356–363, 3)

Identifying an Experimental Two-State Hamiltonian to Arbitrary Accuracy

Precision control of a quantum system requires accurate determination of the effective system Hamiltonian. We develop a method for estimating the Hamiltonian parameters for some unknown two-state system and providing uncertainty bounds on these parameters. This method requires only one measurement basis and the ability to initialise the system in some arbitrary state which is not an eigenstate of the Hamiltonian in question. The scaling of the uncertainty is studied for large numbers of measurements and found to be proportional to one on the square-root of the number of measurements.Comment: Minor corrections, Accepted for publication in Physical Review